HDTV via GNU Radio

NortonDC writes "High Definition TV has been successfully captured in its native data stream from an over the air broadcast by a software defined radio that is Free and open source from the GNU Software Defined Radio project."

Comments

Oh great.

[Big Mark]

GNU TV, where the scripts are open-sourced before the show airs and you know all the jokes before the intro starts rolling.

Mind you, if you knew when to cringe in Nerds (the competitor to Friends, where housebound geeks spend their days in an eternal LAN party with the occasional visit to the pizza parlour) at the "jokes", it mightn't be so bad...

-Mark

Re:Oh great.

[Fulcrum of Evil]

GNU TV, where the scripts are open-sourced before the show airs and you know all the jokes before the intro starts rolling.

How is different from network tv, where the scripts are rehashes of something from 10 or 20 years ago and you know the entire plot (painful jokes included) in the first two minutes.

Re:Oh great.

[gregorio]

How is different from network tv, where the scripts are rehashes of something from 10 or 20 years ago and you know the entire plot (painful jokes included) in the first two minutes.

The jokes aren't that bad if who's watching it's not a bitter person like you are.

Re:Oh great.

[generic-man]

GNU TV would feature some of the funniest shows on television, powered by the Internet's funniest humor archive.

Re:Oh great.

[jd142]

20 years? I wish they were that fresh. Most sitcoms can trace their jokes back to Plautus.

Re:Oh great.

[jdclucidly]

Humor is something an intelligent remark in the context of an ironic situation. Opportunistic bashing of minorities is not humor. Atleast, not for most people.

Re:Oh great.

[jdclucidly]

Queers. Not Aliens. Queers. Opportunistic bashing of gay people is not humor. Further, I'm extremly disappointed in the other moderators that modded me down for simply crying foul. Have we gotten so jadded that critizing someone in a public forum is no longer acceptable? It's our responsibility as human beings to stand up for what we believe in.

Re:Oh great.

[Rasta Prefect]

Queers. Not Aliens. Queers.Have we gotten so jadded that critizing someone in a public forum is no longer acceptable?

I'm curious in what way his sig constitutes gay-bashing. I'd always considered the sig a moderately amusing mockery of conspiracy nuts. Granted "queer" isn't the preferred form of reference for those who date their own gender, but it goes better with the general cant of the sig.

Re:Oh great.

[Anonymous Coward]

http://www.deadmilkmen.com/lyrics/stuart.html

Re:Oh great.

[jericho4.0]

I followed your link.
That was so bad I can hardly even begin to complain....

Re:Oh great.

[Sygnus]

I'm gay, and I didn't find anything offensive about his sig. Lighten up.

Re:Oh great.

[Ponty]

I'm gay. I think his sig is hilarious. I've always thought it was hilarious. I'm a big time Liberal. I think the problem with a dimension of modern liberalism is that people have lost their senses of humor and respond poorly to things that are legitimately funny.

Re:Oh great.

[TXG1112]

It's a line from a very funny song. "Stuart", by the Dead Milk Men. See link for details.

http://www.getlyrics.com/lyrics.php?Artist=Dead+ Mi lkmen&Album=Stuart&Song=Stuart

Re:Oh great.

[unitron]

In your assessment of this situation you have shown perception and intelligence.

There's no place for those of your ilk here on Slashdot. Begone.

In other news...

[Tuxinatorium]

...Scientists at the Smithsonian have decided that GNU is the stupidest acronym in the history of mankind, and decided to make an exhibit about it...

hmmm

[Anonymous Coward]

Sounds too useful to exist.

It will taste the blade of DMCA before the end of the month.

Re:hmmm

[DoraLives]

It will taste the blade of DMCA before the end of the month.

Which ordinarily might goad myself and others to scramble around and get it before the lid gets clamped down good and tight.

Except for one small problem.

When all is said and done, you're receiving television.

Never mind.

Re:hmmm

[yomegaman]

This isn't 'Interesting', it's stupid. In what way would you need to circumvent encryption to receive over-the air TV broadcasts?

Cool, but..... so?

[AvantLegion]

Why am I looking at 4MB images of Lenny Briscoe?

GNU/Correction

[Amsterdam Vallon]

"GNU/High GNU/Definition GNU/TV GNU/has GNU/been GNU/successfully GNU/captured GNU/in GNU/its GNU/native GNU/data GNU/stream GNU/from GNU/an GNU/over GNU/the GNU/air GNU/broadcast GNU/by GNU/software GNU/defined GNU/radio GNU/that GNU/is GNU/Free GNU/and GNU/open GNU/source GNU/from GNU/the GNU/GNU GNU/Software GNU/Defined GNU/Radio GNU/project."

Re:GNU/Correction

[erpbridge]

I think you forgot a GNU/... oh wait, sorry, guess you didn't.

Never Mind.

Re:GNU/Correction

[u38cg]

Gnu are not gnu/funny.

Re:GNU/Correction

[More Karma Than God]

At least all those repeated strings allow them to compress well.

Re:GNU/Correction

[Anonymous Coward]

degnuing your docgnumentation is easy;

sed -es"/GNU\///"g

Not being bothered by Richard Stallman is just as easy.. simply ignure him..

Re:GNU/Correction

[Sygnus]

Not being bothered by Richard Stallman is just as easy.. simply ignure him.

Heh. Sneaky bastard that RMS is ;)

Re:GNU/Correction

[Guppy06]

RMS: "I don't get it."

Re:GNU/Correction

[yomegaman]

I hear that it's also correct to call it 'High DefiGNUtion TV'. Credit where credit is due you know...

Totally 1337 stuff

[Amsterdam Vallon]

Here is the entire collection of mailing list conversations for the entirety of this project's lifetime.

You can see how tough roadblocks were overcome by a dedicated and brilliant team of GNU coders.

Great California Earthquake

[Alien54]

As all of the Movie Studio and TV execs throw themselves a temper tantrum the size of their already oversized egos.

For some life is not fair if things don't go their way all of the time.

news at 11

Re:Great California Earthquake

[yomegaman]

Why would they throw a temper tantrum? Because people want to watch the TV shows and movies that they are broadcasting over the air specifically for that purpose? I don't get it.

Aspect ratio?

[Anonymous Coward]

HDTV is either 1920x1080 (1080i) or 1280x720 (720p). Where did the 2730x1088 resolution come from? It's obviously wrong (the images are obviously scrunched vertically).

Re:Aspect ratio?

[Qzukk]

The page says the images were exported from xine using its snapshot, so maybe the user had the window stretched or something?

Re:Aspect ratio?

[BJH]

Overscanning, most likely - same as what's done with NTSC or PAL to ensure that there's no weird border around your screen.

Re:Aspect ratio?

[Anonymous Coward]

HDTV is digital, other datastreams arent included in the video stream like they were in analog TV. The video feed is exactly that resolution, and it's the TV maker's job to make sure it shows up correctly.

Re:Aspect ratio?

[nedron]

I thought that was weird as well. It looks as though each capture is 1.4 times too wide for the height of the capture. Eg. if you resize the 1001x309 captures to 709x399 (or 1001x565), then you get the correct aspect ratio of 1.77 as the capture looks correct.

It's odd that the captures are this odd aspect reatio. Is this just a problem with the GNU Radio package, or with the way they captured in GIMP?

-David

Re: Aspect ratio?

[shadowhillway]

This is completely wrong. Overscan is a function of a display, not any signal source.

Re:Aspect ratio?

[cpt kangarooski]

Perhaps HDTV pixels aren't square? I really don't know much about the format, but IIRC this was an issue with NTSC. (and some computers have had non-square pixels, including the Apple Lisa, I believe)

Re: Aspect ratio?

[BJH]

You're probably right that I'm incorrect as to the reason for the strange resolution, but overscan can be a function of the signal source - the Amiga was doing it in the 1980s to provide a "full-screen" image.

Re:Aspect ratio?

[mosch]

HDTV pixels are square (HD resolutions 143 1920x1080 and 1280x720 on 16:9 screens). I haven't a damned clue why those screenshots are screwy.

Re: Aspect ratio?

[Thowllly]

Overscaning on the Amiga wasn't actually overscanning anything, rather, it was the normal Amiga resolutions that were underscanned.

Re:Aspect ratio?

[qodfathr]

HDTV pixels are square, and NTSC pixels are not. Perhaps the viewing software was adjusting for rectangular pixels when it should not have been.

Re:Aspect ratio?

[jrs47]

The strange aspect ratio is from a bug in xine-ui's snapshot code.

It assumes that it is dealing with a 16:9 PAL DVD and needs to stretch the picture horizontally to get a snapshot with the correct aspect ratio (because the pixels on a DVD are not square).

resolition

[Anonymous Coward]

Why does the image exceed 1920x1080? Isn't the highest HDTV resolution 1080p?

Re:resolition

[blair1q]

Because they're receiving it from the future.

Re:resolition

[MeanMF]

Why does the image exceed 1920x1080? Isn't the highest HDTV resolution 1080p?

The highest resolution is 1080i, which runs at 1920x1080, interlaced. The GNU project threw in an extra 750 horizontal pixels for free (as in beer).

Re:resolition

[Stonent1]

Well, I watched a show on PBS last night and it said "Welcome to the future. PBS Digital" SO I guess he is right.

Price

[swtaarrs]

How much does the card that they used cost? Is it reasonable?

Re:Price

[Gabrill]

PCI-DAS4020/12 Ultra High-Speed PCI-bus Compatible, 4-Channel, 12-Bit Analog Input Board with Two Analog Output Channels & 24 Digital I/O Channels $1,299.00

a little expensive for my taste.

What?

[ziplux]

Is anyone else really confused about what has been accomplished here? What does GNU Radio do? The site's not too helpful.

Re:What?

[MBCook]

If I am reading it correctly, they used a special radio card under Linux to capture radio waves. Then they ran those waves through a piece of software that could decode them into video, because the waves they tuned into were an HDTV broadcast. The difference here is that they simply record the wave, it's not decoded in hardware. This way they can ues the same card to get FM, AM, HDTV, VHF, UHF, or whatever (in theory). Anyone actually know the answer to this question?

Re:What?

[sulli]

My understanding is that it is a fight against copy protection. Open (Free) software defined radio means that the user can pull down any (unencrypted) broadcast and save it - whether or not the "broadcast flag" (no-copy bit) has been used. In a future in which hardware televisions can't save copies of anything, this will allow the user to save copies and play back later (or do anything else) on a future PC or TiVo. Good stuff.

Re:What?

[josecanuc]

It's not so much a special radio card as it is just any wide-banded data acquisition board and a little frequency-translation unit.

There is a "tuner" that multiplies the incoming radio signals by a variable frequency. When you mix two oscillating signals (by multiplication) you get harmonics. If the variable frequency is just a sine wave (i.e., not modulated with any information), then the harmonics are identical in modulation to the original, but at a difference frequency. The tuning box is used to bring various radio signals down to a frequency that can be digitized by any ordinary data acquisition board.

These data acquisition boards are designed to basically sample voltages of whatever is tied to their inputs, and to sample it very very quickly and very often. Since these boards (and computers also) are getting more advanced (i.e. faster), they are able to sample real radio frequencies (stuff in the ones of MHz ranges).

After you get the signal digitized, it's just a simple matter of writing software that mathematically performs the functions that all the circuitry in the 'old-fashioned' receivers would do with their capacitors, resistors, and inductors (and more).

That's pretty much how it works.

Re:What?

[Qzukk]

From my understanding this is exactly what the project is about: Developing a radio-wave processor that can be modified freely to do whatever you want to the radio waves you capture.

This way you could have just as easily turned the radio waves into music (although it might just come out random static, depending on how you performed the conversion) or done any number of other transforms on the signal.

Re:What?

[NortonDC]

Explanation: What that means is that there is now a free-of-charge and user modifiable software system that can, in combination with hardware built to a freely available specification, use a normal personal computer to recieve and save bit for bit copies of the high definition television signals already being beamed out by broadcasters. That means you can create perfect copies, with color, fidelity and detail that far outstrips what you are used to from standard television or even direct broadcast satellite (like DirecTV), and use them at your convenience and in the full range of uses allowed under fair use, the legal doctrine that gives you considerable freedom to save, copy and even distribute copyrighted materials.

In the long term fight for the maintenance of fair use against the MPAA and the RIAA, it's a very big deal. It's the DeCSS of HDTV.

The current industry/legislature proposals do not lean on encryption, but on a "broadcast flag" that tags broadcast content with what level of freedom viewers have to capture, caopy, manipulate and distribute the broadcast material, with all of the available restrictions imposed at the whim of the broadcaster, to be enforced in the receiver.

Wanna guess what the defaults would be like?

Wouldn't it be nice to have an open, non-proprietary receiver that you have intimate control over?

Re:What?

[Qzukk]

It could be used for that (assuming you have a way to rebroadcast the signal later? Without the FCC hunting your signal down?), but the purpose of the software is to provide signal-processing software targeted at radio signal processing. If that signal is an HDTV signal, than so be it, but it could just as easily be X-Ray signals from space (assuming your sampling device could capture them) or some AM Radio talk show.

If you look at the site you can see a number of other examples. Since you are no longer limited by a standard radio's hardware, you can do completely different stuff like receive two different frequencies at the same time.

Re:What?

[Guppy06]

"It's the DeCSS of HDTV."

Ehh... not quite. As I understand it, the standard is about copying/storing the radio transmission as-is, with no decoding of anything. It would leave any HDCP/"broadcast flags" (if present) in tact.

This is less DeCSS and more copying DVDs bit-by-bit. You'll still need a decoder.

Re:What?

[marcjw]

Oh. Well, that certainly clears things up...

Re:What?

[frdmfghtr]

The images look a little squished, but VERY cool tech-wise. Very cool indeed!

But of course, since the over-the-air HDTV signals are able to be stored and played back with zero loss in fidelity, how long do you suppose that the Minions of Lucifer (aka RIAA and MPAA) scream bloody murder and make this technology illegal using the DMCA as their Evil Shield? After all, if capturing videos and movies digitally will drag down revenues the way that P2P file sharing ALLEGEDLY did (how conveniently they overlook the overall economy) there's now way in Bloody Hell they're going to let their material be broadcast over HDTV, the very TV format that is being legislated into use.

(No, I didn't mistake the RIAA/MPAA for government in that statement...how many reps in DC do you think they already have under their evil greenback spell?)

Too bad that such great innovation and effort gets torn to bits by the almighty dollar.

Re:What?

[wowbagger]

A few nitpicks:

You don't get harmonics (frequencies that are related to the fundimental by an integer multiple), you get mixing products, also known as "sum and difference".

You get harmonics when you feed a single signal into a non-linear element - feed f1 in, get f1, 2*f1, 3*f1, 4*f1,... out. This is commonly used in tranmsitters to allow the use of a lower-frequency crystal to generate higher frequency carriers - you use a 10 MHz crystal, and the feed it into a non-linear element such as a squaring amp, and pick off the tenth harmonic to get 100 MHz.

Mixing involves feeding 2 signals f1 and f2 into a multiplier - you get f1, f2, f1-f2, and f1+f2 out. Mixing allows changing a frequency by a non-integer relationship. You have heard this used in the voice distorters used on TV to mask mob informants - they mix the person's voice with a low-frequency signal to change the pitch of the speaker's voice. This is also the basis of any modern superheterodyne receiver - you mix two different (heterogenous) signals together.

The idea is to take the signal from whatever frequency it is on, and move it to the frequency you have designed your circuit to work at - an "intermediate frequency", or IF. You then filter the signal, amplify it to a specified level, and repeat as necessary to get the signal where you want it. For example, a standard FM radio might go from the broadcast frequency to a 10.7 MHz first IF, then to a 455 kHz second IF, then finally to the FM detector circuit.

Eventually, in a design like GnuRadio, you sample the signal. The tricky bit is you have to sample at a frequency not less than twice the highest bandwidth in the signal (Nyquist's criterion). For a 6MHz wide TV signal, that means you need to sample at not less than 12 million samples per second.

Then, for a system like HDTV, you are dealing with a complex signal - and I mean complex as in sqrt(-1), not just as in "not simple" - you need both the real (in-phase, or I signal - the "real" part) and the quadrature (out-of-phase, or Q signal - the imaginary part). The signal is 8VSB - eight level vestigial sideband. So you have to do carrier recovery and tracking (because the carrier itself was removed - that is what makes it a sideband signal), then you have to convert the signals from the analog RF signal into one of 8 levels (slicing is the technical term). However, you have to slice accurately in 2 dimensions - you have to slice at the correct level (is .7 volts a 6 or a 5?), and you have to slice at the correct time (the symbols are only defined at certain times - any other time the signal isn't valid, it is a blend of the current and the (next|previous) symbol - what is called inter-symbol interference or ISI). So you have to do symbol tracking - figuring out when to sample, and at what levels to slice.

Finally, once you have a symbol stream, you then have to do all the foward error correction - you have to de-interleave the signal (think of unshuffling a deck of cards) - interleaving is done so that a transient interference (like a lightning strike) doesn't scramble adjacent bits - the errors are spread out.

Then you do your block error correction - this can undo a small number of bit errors per block (again, that's why you interleave the signal: so that block error correction needs to only correct a few bit errors per block).

Then you do some more protocol recovery, and you have an MPEG stream.

Normally, you do this sort of stuff with a big FPGA or an ASIC. The GnuRadio folks are doing it in software. The up side is that you can more easily tweak the code. The downside is that you are not going to be real-time for a few more iterations of Moore's "Law".

What gets to be REALLY fun is when, in addition to all of the above, you have to compute parametrics on the signal - not just recover the bits, but measure how far out of ideal the signal was (that's the sort of stuff I do for a living.) When you do that, you have to do all of the above, THEN once you have an error corrected bit stream you have to regenerate an ideal signal and compare the received signal against it, and measure how far away from the ideal signal the real signal is.

And THAT is when you start using multi-GHz processors, 10 million gate FPGAs, big-ass DSPs, and all sorts of other fun stuff.

Re:What?

[awfar]

But it does a lot more, I guess. Since after all the digital emulation of the analog signal, you then have to take that psuedo-analog signal and *once again* find, sychronize, and extract the encoded digital information (mpeg2) stream from that, and then do something with it.

Re:What?

[burns210]

"Is anyone else really confused about what has been accomplished here? What does GNU Radio do?"

Simple Answer: You can watch HDTV on Linux.

Re:What?

[evilviper]

It could be used for that (assuming you have a way to rebroadcast the signal later? Without the FCC hunting your signal down?)

Umm, what?! If you are talking about Tivo-style uses, it's ridiculous to think that the FCC could track down some mW signal that only survives for a few inches. Besides, you could just as well watch the saved broadcasts on a trusty old computer monitor.

Re:What?

[Hercynium]

Granted, I'm mainly asking because you seem to know what you're talking about, but what I want to know is: What hardware is needed for GnuRadio to work?

From the sound of it, it seems like you need an antenna, a tuner, and an a/d converter -- and that's it. The software does all the signal decoding and converting into a format that can be output via screen, speakers, or data stream.

If that's the case, how is it that they claim that GnuRadio can pick up more than one frequency simultaneously? Isn't that a function of the tuner and antenna?

This stuff fascinates me.

Re:What?

[wowbagger]

Yes, basically what you need is a tuner, a digitizer, and enough CPU to do the job. The last one can be the killer, though.

Here's how you can receive multiple signals at once with one tuner - let's pick on ordinary FM, and let's say I want to receive 95.1 MHz and 96.3 MHz.

The first requirement is that the two signals in question have to be reasonably close in strength - if one signal is coming in at -60 dBm (one millionth of a milliwatt) and the other at -120 dBm (one millionth of one millionth of a milliwatt) it's not going to work. But let's say both signals are coming in at -100 dBm, so there isn't a problem there.

OK, so what I do is make a receiver that will amplify all signals around 95.7 Mhz (half-way between the two) and downshift that to a convenient IF, say 10.7 MHz. Ideally, I'd want to bandwidth limit the signal to about 1.5 Mhz - that way I get both the signals I want, and not much else.

So my receiver is now outputting a signal at 0 dBm (1 milliwatt). If I look at that signal on my spectrum analzyer, I see 2 peaks - one at 10.1 MHz (the signal that used to be 95.1 Mhz), and one at 11.6 Mhz (the signal that used to be at 96.3 Mhz).

OK, now I digitize the signal. I need to sample at more than 3 Msample/sec (Nyquist's criterion) - any less and the two signals will be "folded" into one, and it's game over. To keep it simple, I will digitize the signal at 40 MSample/sec.

Now, I have a bitstream that contains the information for both signals. First, I multiply the signal by a mathematically generated cosine and sine wave at 10.1 MHz. This will give me two signals - I and Q. I is the "in phase" signal - the product of the cosine signal and the digitized signal. Q is the "quadrature" signal - it is 90 degrees, or a quarter circle out of phase with "in phase" signal (hence the name quadrature).

Next, I lowpass the signal - I run I and Q through a digital filter that removes all frequency components above 75 KHz.

Now, I compute a four-quadrant arctan() on the I and Q filters - this gives me the phase angle of the signal. I then differentiate that signal - subtract each sample from the previous sample. That gives me the instantanious frequency of the 95.1 MHz carrier - and there's your audio (if you want stereo I have to go trhough a few more steps....)

Now, I do the exact same thing, except this time I use a mathematically generated 11.6 MHz cosine/sine wave. The end result is the 96.3 MHz signal.

Now, as you can guess, that's a lot of math. Hoever, there are chips that do all of that for you. The Intersil 50216 I keep mentioning has 4 independant sections, each of which will do all of those steps, on a 40 MHz signal (or faster), in real time. If you do the math, the chip works out to about 5 to 10 billion operations a second, for 10 watts.

Chips like the 50216 are used by cellular folks - the idea is they grab the entire cellular band, digitize it, and the pull the calls out of the mix. You have only 1 drify, nasty analog receiver section, and hundreds of nice, stable digital sections.

There are a few problems with this approach, however:

1) The wider the receiver, the more noise it picks up. A receiver that is listening to 1 MHz of the spectrum picks up roughtly ten times as much noise as a receiver listening to 100 kHz of spectrum. That extra noise limits what you can tune in.
2) Strong signals in your receiver's bandwidth will prevent you from hearing weak signals - this is called "desense". It's one of the things that makes CDMA and TDMA cellular harder to do than dumb old AMPS - a phone near the tower has to be told to speak softly, so that the tower can hear distant phones.
3) Faster is harder - digitizing a 455 kHz IF is dirt cheap. Digitizing a 10.7 MHz IF is harder. Digitizing a 100 MHz IF to be able to cover the whole cell band is a bitch.

Re:What?

[Giant Robot]

If you have two sinusoids (say 1 Hz, and 2 Hz) and you want to pick both of these up, then you just need to sample at 4Hz (righ?) to get the whole band from 0-2Hz. You can "filter" each sinusoid out afterwards. This is probably a too simple version of it, but the concept is the same.

Re:What?

[NoMoreNicksLeft]

Screw that. I just want a hardware board that will pump the digital bitstream into my computer. QPSK signals, in the 70-130mhz range... what do I need? Besides the seemingly required doctorate in RFE/EE ?

Let me guess, it will be another $1300 card.

*frown*

Re:What?

[wowbagger]

Actually, all I have is a BSEE. That, and 13 years experience in this field.

And what, exactly, are you wanting to decode? The stuff between 70 MHz and 130 MHz you could probably do with the simpler solution that GnuRadio targets - basically a receiver and your sound card.

Narrowband stuff like broadcast FM and the like are pretty easy to do - it's wideband stuff like video that gets hard.

Re:What?

[Defiler]

Where do I learn more about this, other than the obvious BS in EE option?

Re:What?

[shepd]

>It could be used for that (assuming you have a way to rebroadcast the signal later? Without the FCC hunting your signal down?)

100 mW or 1/4 mile at any frequency (Military frequencies might be excepted). Considering your average antenna jack draws 13 mA (1 V/75 Ohms), I think there's no power restriction type problems... Otherwise there'd be no RF modulators! :)

Re:What?

[Giant Robot]

Wow-you really know your stuff from your comments!!

I'll get my BSEE in about two months... It's refreshing, I actually understand all this stuff! (but I don't think most of my classmates do.)

I actually find this GNU radio REALLY cool, I wish they introduced something like this in school earlier. It would be much more interesting to code something that grabs a TV/FM signal digitizes it _AND_ play it on the computer. It wouldn't be thar hard to do with the proper libraries as well, plus the $1300 receiver pales in comparison to other lab equipment.

It sure beats doing repetitive MATLAB/Simulink simulations (don't learn ANYTHING, just cut and paste graphs!). I bet things were a lot more hardcore 13 years ago.

Most of my classmates don't care about learning this stuff, and they will likely graduate without understanding stuff like SSB/VSB, noise shaping, or C (blame Java). Only a few of us are actually interested in this stuff sigh...

Re:What?

[nathanh]

Strong signals in your receiver's bandwidth will prevent you from hearing weak signals - this is called "desense". It's one of the things that makes CDMA and TDMA cellular harder to do than dumb old AMPS - a phone near the tower has to be told to speak softly, so that the tower can hear distant phones.

Does this mean denial-of-service attacks against CDMA towers are easier than similar attacks against AMPS? Just tell your phone to "speak" as loudly as possible and ignore the tower's request to be quiet? I'm assuming AMPS is what GSM phones use? I recently read a New Scientist article on how GSM cells and phones work, but it didn't go into any detail for CDMA.

Re:What?

[roybadami]

AMPS is the old US analogue system.

Re:What?

[wowbagger]

I agree with BigBlockMopar - I regret not taking the extra time to get my BAMath - if you get a BSEE you are only a few credit hours from a BAMath. And for this sort of work, LaPlace is your buddy - almost all this work involves working in the LaPlace domain (or transforming into the z domain for digitial systems.)

I'm rather the inverse of BigBlockMopar - I don't do the electromagnetic field theory, rather I do the modulation and software engineering work.

Get a degree, get a ham license, get into a shop that does this - Motorola, Ericcsson, E.F. Johnson, Agilent, IFR/Aeroflex, anybody like that.

Re:What?

[wowbagger]

Well, when I do the IF filter designs for the digital sections, I generally use Matlab/Signal Processing tool or Mathcad - if you think I to the inverse FFTs by hand you are crazy. But yes, when I was an undergrad, I had to work through all the equations by hand - an assignment took hours to complete</voice>.

However - yes, if nothing else start playing around with DSP using your soundcard - practical experience rules!

As for your classmates - yeah, I had fun during my labs:
them: "OK, which one is the 1k resistor?"
Me: "Uhh... This one."
them: "How do you know? You didn't measure it!"
Me: "Brown, Black, Red - 1K"
Them: "Huh?"

Of course, I was the guy who brought his own logic probe, ICs, prototyping board, oscilloscope, and databook to digital logic class - my brother had given me these back when I was 12 (Thank you, Bob - RIP).

And I do almost ALL my work in C++ - without multiple inheritance Java won't cut it (and speed is king, as well).

Re:What?

[NoMoreNicksLeft]

The signal I want to listen to is likely QPSK (though I can't be sure, there is a slight chance it is QAM16). Speed is approximately 2.5mps... exact frequency is 75.25mhz (though I'd like to be able to do up to about 130mhz later on). Other than that, I don't know much else about it... kinda the reason I want to listen in.

The reciever/sound card sounds cool, but I still don't really know what I need.

Re:What?

[sjames]

Even though real time conversion is not realistic for a few more CPU generations, just having the whole thing implemented (and documented) in Free software is a big benefit. It at least provides a good template for a Free FPGA design.

Re:What?

[smallpaul]

What does it mean to "decode" a flag? You just ignore it!

Re:What?

[wowbagger]

OK, perhaps you could tell me WHAT you are wanting to listen to - then I could probably tell you the protocol.

But if you are looking at a 2 MBaud signal, you aren't going to be able to do this with simple stuff - you will need a fast digitizer card.

And if it is a QPSK or QAM signal, you are going to need a good tuner.

Re:What?

[NoMoreNicksLeft]

The out of band data signal on digital cable TV. Sometimes referred to as the FDC. I know the frequency, and I'm fairly certain of the modulation. I have a pretty good idea of what sort of data to expect on it, but I would like to be able to know for sure, one way or the other.

Sweet! OpenSource HDTV!

[digital photo]

Wow, guess that's one less application I would need to worry about needing specialized hardware for. Time to fire up the ol'deb box...

Wonder how much those cards cost... :|

Price and Distributors

[i_am_nitrogen]

I've tried various google searches for terms like MC4020, MC4020 data acquisition card, MC4020 data card, etc., and the only results that actually refer to a data acquisition card of some kind are on either the gnu radio page, or the MC4020 Linux kernel driver mailing list archive. I can't find pricing or distributor info anywhere.

If it costs less than $400, though (which is unlikely), I'd pick up an MC4020 instead of a traditional HDTV tuner card.

Does anybody know if atsc_rx can be run realtime?

Re:Price and Distributors

[dmanny]

I posted mfgr link in comment below. $1300

Re:Price and Distributors

[MShook]

Yuck...

Cool, but how fast is it?

[chafey]

Definitely looks cool, but I couldn't find any information about how long it takes to process each HDTV frame. I doubt it is nothing near real time!

Re:Cool, but how fast is it?

[tjp]

The A->D card costs that much because it can sample the high frequencies used in radio (up to 20Mhz for this card; compare to your plain old sound card that can only sample up to 44Khz). That part is indeed realtime (otherwise you wouldn't get all of your data...). It's the software running on the host PC that isn't realtime (yet), due to the large amount of processing required for HDTV.

Hardware

[Ed Avis]

So, can I go out and buy off the shelf suitable hardware to use with GNU Radio? Assuming I have a box with a reasonably fast CPU and a spare PCI slot. The web site seems strangely coy about covering this, unlike most driver sites where they say 'we successfully got working the card XXX from manufacturer YYY, available for $44.50 from ZZZ'.

Do I need an A/D converter, or what? Knowing nothing about electronics, where do I get such a thing? I just threw away my BBC Micro with its built-in 12-bit A/D... was that a mistake? ;-)

Re:Hardware

[josh crawley]

No, you need a very expensive DSP board. I'm guessing it's about 500-600$ here in the US. Look at my other post in this thread for the site.

Re:Hardware

[Ed Avis]

Well, it looks like a DAS4020 board has 12-bit resolution and so does the BBC Micro (although it might be only 10 bits in practice). The difference comes in sample rates: 20MHz versus 100Hz! So people are not going to be recording any UHF broadcasts through the analogue port. Unless they manage some serious overclocking.

Re:Hardware

[Beryllium Sphere(tm)]

Depends on what you want to do. Eric Blossom answered this very same question here at Codecon.

Remember that you don't have to do HDTV. The concept here is to have a universal radio, one that can be an FM receiver, a garage door opener, or something nobody's ever thought of yet, just by loading appropriate software in the DSP.

You can get into the math and maybe solve some real-world problems by using the audio output of a normal narrow-band radio receiver as your source and your sound card as your ADC.

Yes, I mean real-world problems. Amateur radio operators are using an audio->sound card->DSP software system called PSK31 to communicate through noisy bands with modest power and ultra-narrow bandwidth.

If you want to do other cool things like listening to every radio transmission at the same time, the hardware demands go way up.

Neato..

[josh crawley]

Seems really neat, but I found that card on a science site. ONLY 1000 pounds (Great Britan). I suspect that this isn't much cheaper in the US either ;-(

https://directory.adeptscience.co.uk/controller. js p?action=GetProduct&pid=91&sid=1

Those aspect ratios are off.

[kalgen]

The images on the site are at 2740x1088 resolution, but HDTV at max resolution is 1920x1080. You can tell from looking at the images that they're horizontally stretched, so something weird is going on.

Nice

[sulli]

But will they implement the Broadcast Flag?

Good And Bad

[sidespace]

A Linux-friendly HDTV recording solution is definitely needed. Unfortunately, it seems that in order to record HDTV you need a $1300 Analog Input Board.

Can anyone with more knowledge about this project please post a less expensive solution if one exists?

Re:Good And Bad

[Maxwell]

The 20Mhz is the killer thing here. That is some Serious converting. Your Cd player converts DA 16bits at 44khz. A high end studio type- audio card does 24bits at 96khz, in either direction.

This thing is doing 12bits at 20,000khz. Holy crap. That is hauling ass, hope your damn good with a sauldering iron !

JON

Re:Good And Bad

[Enraged_jawa]

please post a less expensive solution if one exists?
There are lots of DTV tuner cards available on EBAY, (Hauphauge Wintv-D comes to mind) for around $100 that include capture to disk.

Holy run-on sentences, Batman!

[Rayonic]

"High Definition TV has been successfully captured in its native data stream from an over the air broadcast by a software defined radio that is Free and open source from the GNU Software Defined Radio project."

Huh?

Re:Cool

[Thing 1]

Can I FTP the second season of west wing yet? No? Okay then

You can get many TV shows you might have missed by using BitTorrent .

This site has a list of links to various sites which contain TV shows available through BitTorrent.

A West Wing episode is available here (The West Wing - s04e16 - California 47th [ftv].mpg.torrent) (but you need to have installed BitTorrent prior to clicking on that link).

I don't follow West Wing so I don't know whether that's from second season, and your comment is accurate -- that's the only one available from that site. One other is The.West.Wing.S04E14.Inauguration.Day.Part.I .

Enjoy!

Broadcast flag?

[Corrupt System]

Shouldn't this project be illegal under the new FCC broadcast flag rule. Unless it incorporates DRM to force the user to respect the broadcast flag, that is.

Re:Broadcast flag?

[Wesley Felter]

The broadcast flag is a proposal, not a regulation. But if the broadcast flag is issued, it sure looks like GNU Radio will be illegal.

Re:Broadcast flag?

[ColaMan]

Maybe it *will* be illegal in your country.

But eventually Supply and Demand will kick in - someone will want to tape "Friends, 2009", so presto! the means will appear. Soon enough you'll be able to buy the equivalent HDTV VCR from China for $120 that "mistakenly" ignores the broadcast flag, a-la DVD zoning.

Pity it means that some other country's tech industry gets the "3) Profit!".

Side note:
Sure won't be worrying about how illegal it is in my country (Australia) for a long while yet.
Is "the switch" happening in 2008? And have we sorted whether we're going for SDTV or HDTV?
Anyone with a set-top DTV box in .au care to comment on the current digital transmissions?
Anyone? Anyone? Bueller?

Re:Broadcast flag?

[Guppy06]

"Pity it means that some other country's tech industry gets the "3) Profit!"."

Look on the bright side: At least we're allowed to use shortwave receivers.

Speaking of HDTV in Linux...

[i_am_nitrogen]

Does anyone know where to find an HDTV tuner card with drivers for Linux? I'd really like to move my whole theater into the digital domain, without installing Windows (which is DEFINITELY not the right tool for the job, so don't give me one of those "use the right tool for the job fool" posts.. Windows is never the right tool for the job, unless the job is to annoy your boss/employees/coworkers and waste all your money).

Re:Speaking of HDTV in Linux...

[Wesley Felter]

There are none. Check the Linux HTPC AVS forum for plenty of whining on this topic.

Re:okay...

[t0ny]

it means that now you can pirate an HDTV program, buy sawing out the commercials and saving it to your hard drive.

Think TiVo, except its easier to get at the saved programming

Top 5 reasons to process HDTV signals on your PC

[Amsterdam Vallon]

5 -- You think a $3,500 computer with a 17 inch monitor is better than a $2,000 HDTV set with a 35 inch screen

4 -- You wanna take screenshots of Joe Millionaire and set them as your desktop wallpaper

3 -- You're unemployed and have nothing else to do aside from incessant blogging

2 -- Regular TV is _so_ '90s.

1 -- Record Cinemax skin flicks as part of the Masturbate For Peace campaign

Courtesy of The *nix Top 5

Cost: $1,299.00

[jdclucidly]

At $1,299.00 for the PCI card that their driver is written for, I do not see this in my future. For that matter, I don't see that in the future of many hobbiests which makes this project rather useless to the general population at present.

See here for information on the product the GNU Radio project wrote the driver for: Measurement Computing

Maybe some day...

Re:Cost: $1,299.00

[cybermace5]

By taking this defeatist attitude, you are creating a self-fulfilling prophecy.

The card is $1,300. The reason is economics: people do not buy them in mass quantities, therefore they are rare and expensive. These cards are typically used in fringe high-tech situations, and honestly $1,300 is an awfully good deal considering what the same capabilities would have cost five or ten years ago.

If the card is already down to $1,300, instead of $13,000 or $130,000, the price can be reduced to $130. Once software radio becomes a demanded product, the push to increase production will make the cards more available.

Again, if you want to play around with cutting-edge tech, the card is pretty inexpensive. I've been dealing with high-speed video vendors who want $60,000 for essentially an overclocked VCR. And that's half of what they cost ten years ago.

These guys have done something few are able to do: take an idea and actually follow it to completion. The first personal computers weren't cheap enough to give away in cereal boxes either, so give this some time and encouragement.

Re:Cost: $1,299.00

[More Karma Than God]

Don't bet on that kind of price reduction due to quantity.

You have to get the quantity first, before the prices go down. But until the prices go down you can't get the quantity.

It's the chicken and the egg problem all over again. You can't get chickens without eggs, and you can't get eggs without chickens, therefore neither chickens or eggs exist.

For receiving HDTV signals wouldn't it be cheaper to buy a tuner and put a high end vidio capture card in your PC? Control the tuner using LIRC for an integrated system.

Re:Cost: $1,299.00

[Anonymous Coward]

Name one, just one, hi-tech device that hit the market at a consumer acceptable price. Calculators? Digital cameras? Televisions? VCRs? Assuming you weren't demonstrating the concept of redundant, what's your point?

Re:Cost: $1,299.00

[cybermace5]

For receiving HDTV signals wouldn't it be cheaper to buy a tuner and put a high end vidio capture card in your PC? Control the tuner using LIRC for an integrated system.

Might be cheaper to do that for HDTV.

But would the same setup be able to do broadcast TV, cable TV, slow-scan satellite feeds, AM and FM commercial broadcast, ham radio, weather radio, police and other emergency bands, shortwave, CB, and whatever else exists?

If the software radio can do all of the above, many would jump at the opportunity to pay only $1,300 for the necessary piece of hardware.

If they ever get transmit capabilities, this will be a seriously wicked piece of technology (ignoring the impossibility of ever licensing the monster).

Re:Cost: $1,299.00

[matts.nu]

Don't bet on that kind of price reduction due to quantity. You have to get the quantity first, before the prices go down. But until the prices go down you can't get the quantity.

Wrong. You have to get the demand first, but not necessarily the quantity.

Re:Cost: $1,299.00

[More Karma Than God]

True, but most folks don't need/want all that stuff. A few dedicated devices would still be cheaper.

Re:Cost: $1,299.00

[More Karma Than God]

I'll bet you're one of those folks who believes in the existance of chickens despite the fact that the only way to get chickens is from eggs and the only way to get eggs is from chickens.

Re:Cost: $1,299.00

[DickBreath]

At $1,299.00 for the PCI card that their driver is written for, I do not see this in my future. For that matter, I don't see that in the future of many hobbiests which makes this project rather useless to the general population at present.

Rewind to about 1977.

At the prices of these so called "personal computers" that these hobbyists tinker with, I don't see one in my future. Such an expensive device doesn't serve any useful purpose.

Have a little bit of vision. Please. How much were sound cards when they first appeared? CDROM drives? Etc. Just imagine a possible future...

Imagine... An IF/RF card is a modestly priced PCI card.

Imagine the software applications for this card...

• AM / FM radio
• NTSC television
• Shortwave radio
• GPS receiver
• Walkie talkie
• Cordless microphone
• Police scanner (but because it is software, it is not artificially "restricted" to only certian bands, such as excluding cell phones)
• Cell phone implemented entirely in software (how about a cell phone that supports all standards. GSM 1800, GSM 1900, PCS, TDMA, CDMA, and Analog)
• Baby monitor
• Bluetooth (with the radio part done in software)
• Remote Controlled car transmitter (software that controls those radio controlled cars, by doing the "radio" part totally in software)
• X10 radio transmiatter or receiver for remotes
• Transmit or receive garage door opener signals on your computer using some application you download from Freshmeat

Use your creativity. Imagine possible uses. The uses will drive economics.

Microprocessors in many embedded systems are overkill. Do I need a microprocessor in a Microwave Oven Controller? No, just some dedicated logic circuits would do. A custom chip. But a microprocessor with firmware is easier and quicker to do. Of the shelf parts. Just send the manufacturer your firmware, and they "manufacture" it into a single chip that has microprocessor, RAM, ROM (your firmware), VIA's, timers, I/O ports, etc. Yes, overkill. But easy and flexible.

Now instead of software replacing just "logic" hardware and "controller" hardware, imagine software also replacing "radio" hardware.

Just as open source is a disruptive technology; and just as open source and other audio/video encoders/decoders, P2P, and cheap broadband upset the RIAA/MPAA; just imagine how freely available software defined radio would upset many other powerful interests. For example, right now you can't get a scanner that will pick up analog cell phones because some idiot legislated it to be "secure".

Just think about every use of radio waves for any purpose, like the keyless entry thingy on your keychain that unlocks your car doors from a distance. Imagine what software defined radio could do?

Imagine some hypothetical PDA that has an antenna, the necessary IF/RF hardware, and all of the above applications running on that PDA. In fact, such a PDA would be a "universal gadget". One moment it is a pocket TV. Another moment it is a walkie talkie. Then just run a different application and it is a cell phone. Then a hand held GPS receiver.

Re:Cost: $1,299.00

[jdclucidly]

Read my post again. I clearly state: "which makes this project rather useless to the general population at present "

Not only that, but then I clearly state "Maybe some day..."

I agree this is a good thing but it needs to come down in price before most of us can afford it. If you had read the other posts, you might have seen that someone suggested this could be built for under $500.

Calm down...

Re:Cost: $1,299.00

[DickBreath]

Yeah, I have read some of the other posts.

Yes, I probably am too excited by the possibilities.

I did see some interesting discussion of hardware involving custom FPGA's. I also think the possibilities of "open hardware" are about as equally interesting. When anyone can reasonably cheaply make their own custom reasonably large scale IC's, things will change.

Just as open source is a disruptive technology. So will be software radio, and open hardware.

What exactly do I need to buy? And other FAQs

[Anonymous Cowdog]

What exactly do I need to buy to start playing with this?

I'm more interested in the radio part than the TV part, but either way, the site doesn't give any indication of whether this is within the reach of the average geek or not.

What do we need, a TV tuner card with FM, or no card at all (is that why it's called software radio)?

If a card is needed, which cards satisfy BOTH of the following two conditions: 1) the card works under Linux/BSD and 2) the card is actually still available on the market today. (I ask that last part because of experience with old cards being supported, but not available in stores, for other functions like video and networking). And how much does the card cost? Is an antenna required? How much does everything cost?

Someone please clue us in. Thanks.

Board cost $1300 but computational time?

[dmanny]

Here is a link for the board. $1300 is a little high for my budget but increased quantities would drive that down.

I have not yet got a feel for the computational power required to approach real time processing or typical performance. Does anyone else know?

Re:Board cost $1300 but computational time?

[Wesley Felter]

40 times slower than realtime (on unkown hardware).

Re:Board cost $1300 but computational time?

[dmanny]

Firstly, thank you for finding that metric for all to see. I was coming up empty.

Secondly, 1/40th real time? My first reaction is ouch. My second is 'Well...so?' I have two Tivo's and I can tell you from experience that we do not recieve a worthwhile signal 1/40th of the time. I should say worthwhile in content quality -- signal quality is fine but most content is crap.

Still this is unoptimized performance. I wonder to what extent distributed processing, ala reusing a Cinerella render farm, might help. With the input being primarly a chronological stream, I don't see much issue. Just break up the signal with a little bit of overlap...

Re:Slashdotted

[claygate]

You would think gnu.org might be able to take the /. effect? I'm just downloading some of the 4MB .pngs to see who well their server holds up. There should be about half a million people doing the same in a couple minutes.

The most painful part of that?

[Merk]

Looking at the images and seeing that huge ugly NBC bug in the lower-right corner. You'd think that at HD resolution the least they could do is make it smaller, but no. At least this was on the original broadcast network. When I watch The Daily Show on Canada's comedy network they plaster their opaque bug on top of the original comedy central one, and as a result I every so often miss out on something that the bug is crawling over. Is there any hope of HDTV killing these things? If it's a digital signal couldn't they transmit the bug out of band and let the TV reconstruct it when people change channels or something?

Re:The most painful part of that?

[91degrees]

No.

Sorry, but I'm afraid you want that bug. It's a fundamental part of your viewing experience.

Re:The most painful part of that?

[GoRK]

What would be useful is writing an algorithm for some media player, xine for instance, that would detect and filter out any bug in the corner. You'd lose some (or a lot) of the color detail, but you could get rid of it.

Then implement it in a TV!

Hardware....

[wowbagger]

Man, I wish the Gnu folks would build their own hardware card rather than the card they are currently using - it's quite expensive.

I'd love to see them put a decent FPGA, an Intersil 50216 4 channel digital downconverter, and a nice 60 Msample/sec 12 bit flash A/D converter on the card - they could do that for a bill of materials of about US$200, and have enough power to do the capture properly.

Before you say "Fine - why don't YOU design it?": I'd love to get more involved in GnuRadio, but I'm afraid of potential conflicts of interest both ways - contaminating GnuRadio with my professional work and possibly exposing my employer to problems with GPL infringment.

Also, is anybody big in the Gnu Radio project going to be at IWCE (International Wireless Convenention and Exposition) March 10 - 14? If so, where? I'm getting in on an exhibitor's badge - maybe I could get pictures?

Re:Hardware....

[josh crawley]

Wowbagger, read the post I just posted and follow the link to the FSF.. You're actually quoted on there for asking a GnuRadio question ;-)

Surprise! You're on Slashdot camera.

Re:Hardware....

[wowbagger]

Well, I DO do this stuff for a living, as well as being a computer geek and a ham.

But really, $1300 for the digitizer card is a bit steep - I work with a system using a 40 MSamp/sec 12 bit flash converter and Intersil 50214. The Intersil is about $30, and I don't think the flash converter is much more. Add a $50 FPGA to do the interfacing to the PCI bus, and you could do scatter-gather busmastering capture to the main system pretty easily.

Use a $50 Intersil 50216, and you could do most of the heavy lifting with it - Final IF filtering, I/Q recovery, post-detection filtering, symbol tracking, etc. That would remove a lot of the CPU load from the system, possibly allowing for real-time aquisition and decode.

Go to one of the board fab houses, and you could probably get a board built for about $500, maybe less.

Considering that people are spending $500 for video cards, this might not be so bad.

Re:Hardware....

[cheese_wallet]

"Add a $50 FPGA to do the interfacing to the PCI bus"

PCI interfaces aren't exactly simple. It could take a very long time to write your own pci interface from scratch. I haven't been to opencores in a while, but it looks like their PCI core is done. Has anyone tried to use it?

Re:Hardware....

[wowbagger]

Yes, things like a PCI core are DEFINITELY something you want to be able to use, not create!

That's where Gnu + hardware is a great thing - opencores and the like are GREAT ideas.

Re:Hardware....

[ChrisDolan]

I'd love to see them put a decent FPGA, an Intersil 50216 ... could do that for a bill of materials of about US$200

Have you considered donating the hardware? Since you can't participate in the coding, as you have explained, perhaps financial support is more in order.

Re:Hardware....

[benjamindees]

Are you suggesting something like this?
(I'm actually curious. At $750, this seems much more reasonable than the $1300 device listed above.)

Re:Hardware....

[wowbagger]

6 Msample/sec at 12 bits is a little weak for this sort of thing - I'd either want more bits or more speed - prefereably more speed, like 40 MSample/sec or better.

Re:Hardware....

[wowbagger]

I'm not sure what you mean by "donating the hardware" - do you mean giving the GnuRadio folks a sample board, or what?

The problem is this: even if I wanted to give them a sample board, I could very will a) get in trouble with my employer, since that's what we do for a living, and b) get the GnuRadio folks in trouble by causing them to infringe on my employer's intellectual property.

That's the rub - I'm too close to this thing to safely get seriously involved. It would be like one of the core folks on the Windows software team being involved in the Wine project.

Re:Hardware....

[ChrisDolan]

Ahh, it was not clear from your previous post that the board you were advocating was made by your company. Why not get your company to donate a sample board rather than you do it yourself? Surely it could only help sales if you got more people writing software for your board. Or are you saying that the money your company makes is on the software for the board? Gnu Radio is your competition?? If that's the case, well, this is a pretty pointless discussion.

Re:Hardware....

[nathanh]

Well, I DO do this stuff for a living, as well as being a computer geek and a ham.

But really, $1300 for the digitizer card is a bit steep - I work with a system using a 40 MSamp/sec 12 bit flash converter and Intersil 50214. The Intersil is about $30, and I don't think the flash converter is much more. Add a $50 FPGA to do the interfacing to the PCI bus, and you could do scatter-gather busmastering capture to the main system pretty easily.

Well I don't do this stuff for a living, and I'm exceedingly jealous of people who do :-) However I reckon the reason that the card costs $1300 instead of a mere $200 is because the company is trying to recoup R&D costs as well as turn a tidy profit. Prices will drop as demand increases and from what you're saying those prices could drop as low as $200. I can't wait!

Re:Hardware....

[wowbagger]

We don't make the board as a seperate product - it is a part of a piece of test equipment we sell. What makes our equipment worth the money is the total package - software and hardware. GnuRadio might not be a competitor, but.... Once you can digitally recover the signal, doing the parametrics on it is just more programming. So in theory GnuRadio could be a competitor.

<personal opinion !employer opinion>
I'd welcome the chance to work with GnuRadio - most of the protocols we work with are patented and licensed, and GnuRadio probably couldn't implement them legally, and so couldn't compete. However, I'm not a C?O - just a senior engineer. I don't set policy, and somehow I doubt the muckety-mucks would go for this.
</personal opinion>

Re:Hardware....

[wowbagger]

However I reckon the reason that the card costs $1300 instead of a mere $200 is because the company is trying to recoup R&D costs as well as turn a tidy profit.

Yes and no. This card is a standard card that folks like me would use to build a system, so they don't sell in quantity, so the non-recurring engineering costs aren't amortized over a large number of cards.

However, this card is also pretty over-engineered for what the GnuRadio folks use - that is why I think that a dedicated RF capture card would a) do a better job and b) be less expensive overall.

(now, I wait for the 2 minute comment timeout. Dope-de-doe).

Tangential Q

[sam_handelman]

I have a TV tuner card which takes the feed from my cable box.

Does anyone know of any software that would enable me to unscramble cable signals in software? The tuner controller runs from software, but I can't use my computer as a TIVO b/c I have to use the cablebox to get anything.

google cache

[TerraFrost]

here's the google cache of the site: http://216.239.33.100/search?q=cache:KWJY96KyuCAJ: www.gnu.org/software/gnuradio/ also, if you're interested in HDTV samples, this site has a bunch of HDTV trailers (complete with Dolby Digital 5.1 surround sound, as per the HDTV spec): http://www.eecs.umich.edu/~balazer/hd_ads/

Rough Explanation

[tweakt]

I'm not 100% up to speed about this, but I saw the project explained at Defcon last year...

Bascially the aim is to drastically decrease cost and increase flexibility of radio signal reception and decoding by replacing lots of specialized electronics with software.

Now instead of a very expensive ATSC decoder for your HDTV-Ready TV, you will now have a box with an antenna, maybe a preamp, and a powerful DSP running in software.

The cool part is, you can reprogram or adjust the software as needed to create other capabilities, use other frequencies, or increase performance even after the product is shipped.

I'm sure I drastically oversimplified this, and probably don't realize the full scope of the benifits. Read up on it, use google.

But as applied to HDTV, this is an AMAZING accomplishment. We might soon have open-source HDTV decoding. I for one, would love to have the ability to directly access the native format of the TV signal, stream it to disk, multicast it on my home lan to the living room, whatever. COOL STUFF!

Re:Rough Explanation

[SN74S181]

Intel tried to do this about five years ago. The project was called Native Signal Processing, or NSP. The idea was to do DSP in the main processor, and eliminate the specialized DSP chips in PCs.

It was a failure, except for one product that came out of it. The WinModem.

Re:Rough Explanation

[unitron]

"It was a failure, except for one product that came out of it. The WinModem."

I see that success is very much a matter of perspective.

Re:Rough Explanation

[SN74S181]

If you weren't there to see the hype, you'd realize that they promoted NSP as something that we should ALL learn. That it turned into a single niche closed-source product is a significant failure.

Re:Rough Explanation

[unitron]

Nothing spoils humor quite so much as having to explain it, but I was trying to snidely make the point that not all of us consider the "success" of the Winmodem to be a good thing. Without it 56K modems with all the necessary hardware on board to do the job without burdening the CPU or locking you in to a particular OS would have been in higher demand which would have led to more choices at lower prices as happened with the 33K modems after a year or so.

For those who miss the point

[tweakt]

Here's the quick version from the site:

GNU Radio is a collection of software that when combined with minimal hardware, allows the construction of radios where the actual waveforms transmitted and received are defined by software. What this means is that it turns the digital modulation schemes used in today's high performance wireless devices into software problems.

Read the site! This is very important stuff and could have a huge impact on technology.

Re:For those who miss the point

[TheRaven64]

In my world, the phrase 'minimal hardware' does not include a $1300 PCI card...

Re:For those who miss the point

[anthony_dipierro]

In my world, the phrase 'minimal hardware' does not include a $1300 PCI card...

True, for now, but in theory the price would be able to be brought down to less than the current HDTV tuner cards (and act as an 802.11 card to boot).

Re:For those who miss the point

[Anonymous Coward]

The goal is to have minimal hardware requirements. Right now, it's not like that. So either help em out, or quit complaining.
Nuff' said.

Re:For those who miss the point

[exhilaration]

... and lets you listen to your neighbor's cordless phone conversation, lets you peek into GSM/TDMA mobile phone traffic, lets you listen to your local police CB traffic, lets you control remote control cars/planes/etc., lets you open your garage door from your desk

oh yeah, it also gives you TV/HDTV/FM/AM - maybe even satellite radio (but that's probably encrypted).

This is a *universal* radio - you just have to write software to make it do what you want.

Re:For those who miss the point

[Anonymous Coward]

...(but that's probably encrypted).

As are your neighbor's cordless phone, GSM/TDMA mobile phone traffic, police CB, and your garage door opener. Next.

Re:For those who miss the point

[Anonymous Coward]

...(but that's probably encrypted).

As are your neighbor's cordless phone,

Read the package carefully. Most cordless phones only encrypt the phone's identity so no one can remotely make calls over your phone line. It is incredibly difficult to find a cordless phone that also encrypts the conversation.

GSM/TDMA mobile phone traffic

I have no idea.

police CB

Many police departments do not encrypt their radio traffic.

and your garage door opener.

Many new garage door openers encrypt the signal. Countless older garage door openers do not.

Next.

The remote keyless entry on most cars does not encrypt the signal.

Re:For those who miss the point

[Wesley Felter]

GSM crypto was broken at Berkeley.

Re:For those who miss the point

[jquirke]

GSM/TDMA mobile phone traffic

I have no idea.

Is encrypted, however some versions of the algorithm (A5/1) are flawed, not to mention the authentication/key generation A3/A8 (implementation specific, but most telcos use COMP128)

Re:For those who miss the point

[topham]

check Slashdot for the story, but forget about the security offered by garage door openers.

Atleast 1 brand has a reset sequence which resets an internal counter and would make it quite easy to duplicate the required signal to open the garage door.

ah well.

DAS4020/12: $1300 US, 1200 pounds GB

[i_am_nitrogen]

I found out by downloading the kernel driver source code that the name of the board is actually Measurement Computing DAS4020/12, and costs $1300. Thanks to the other posters for also mentioning this.

Re:Slashdotted

[ahaning]

Try one of the GNU mirrors:

http://gnu.sunsite.utk.edu/software/gnuradio/image s/hdtv-samples.html

http://gnu.wwc.edu/software/gnuradio/images/hdtv-s amples.html

http://gnu.mscnetworks.com/software/gnuradio/image s/hdtv-samples.html

http://www.phildowd.com:4060/software/gnuradio/ima ges/hdtv-samples.html

Basically, append software/gnuradio/images/hdtv-samples.html to any of the links from here: http://216.239.57.100/search?q=cache:1KyAbWv9nRAC: www.gnu.org/server/list-mirrors.html+gnu.org+mirro rs&hl=en&ie=UTF-8

Yeah. Until they make it illegal.

[rice_burners_suck]

I give it not one month and the RIAA, MPAA and Microsoft will be jumping on this like flies on poop to make this illegal. I can already see all kinds of garbage being invented that will make HDTV more expensive and less flexible for consumers in order to protect the alleged rights of huge multinational corporations to eternal perpetually increasing profits.

All of the above represent part of the reason that I have completely stopped watching television. Did I mention that I don't purchase software that has any sort of copy protection? That's true as well.

The best way to fight DRM, copy protection, and all this trash legislation is to speak with your money: Don't buy products containing this crap. You could go further and do what I do: I buy the competition's product and then send a letter (not an email but a letter on real paper in a real envelope with a postage stamp and my real address on it) telling the company WHY I have just purchased their competitor's product as opposed to theirs. Nanny nanny boo boo.

Re:Yeah. Until they make it illegal.

[Anonvmous Coward]

"I give it not one month and the RIAA, MPAA and Microsoft will be jumping on this like flies on poop to make this illegal."

Ya had me until you mentioned Microsoft. What do they have to do with anything? Pardon my pessimistic attitude, but I can't help but think that was an attempt at karma whoring. Explain to me why I'm wrong please?

"Did I mention that I don't purchase software that has any sort of copy protection?"

What's the point of that? I'm going to defend software companies (particularly game companies) here. They haven't been terribly abusive about copy protection. You can (usually) back up your stuff. On top of that, when it comes to sampling things like games, you usually have demo versions available. Need to install your software on a second computer? Nothing really preventing you from that unless you have a hardware lock. Even Microsoft's okay with that. Office's license allows a for a second copy to be installed on your laptop as well as your desktop. I can honestly say that I think software companies have a much better idea about how to protect themselves without raping the customers than content industries like the *AA does. What software companies do can usually be considered true copy protection, not restriction like the *AA is promoting.

Not buying copy protected software is not making much fo a stand. Software has a much better reason to protect it's works than the Television Industry does. As a matter of fact, save TurboTax and Windows XP's insistence on calling home, I can't think of the last time anybody got overly uppity about software protection. So I ask you again, did you really have a point or are you karma whoring?

Re:Yeah. Until they make it illegal.

[Anonymous Coward]

Yes, that would be like making tubing and hairspay illegal because you can make a potato gun. Or like banning code to read a DVD because you might be able to read a DVD that the RIAA didn't want you to read.

Specifically, forces in opposition to a free society are considering FCC rules that would require all commercially available radio receivers to have some sort of "tamper resistent" properties. This won't affect you and me because we will build our GNU radios from chips sampled or purchased, or get them in El Paso from those Mexicans who already manufacture cable boxes across the border. But it will effect your mother, your friends, and others, because they will pay more to see less on the TV.

If you keep voting ignorant testicle-less corporate serfs into office, you will live in a society which resembles IBM's or EDS's corporate culture EVERYWHERE, not just in the workplace.

Re:Yeah. Until they make it illegal.

[cpt kangarooski]

I'd be happy to do so.

Basically, I think that self-help is unacceptable in conjunction with the legal protections conferred by copyright.

That is, a copy protected piece of software will never stop being copy protected. Even when the copyright holder loses their rights in the work. I'm fully prepared for copyrights to be granted, and for copyright holders to be able to pursue me for infringing on the rights.

BUT only where I stand to benefit from this as an ordinary person or author. Which means that I expect that after a reasonable period of time, I should be able to use, copy, alter, and base derivative works upon it. Upon any copy, with no particular difficulty beyond something inherent in the medium and not used as a deterrant. (e.g. a CD needs a CD player, but there's little special about that; adding encryption to it is not ok)

If someone wants to release copy protected works, then I think that they should do so without benefit of a single legal remedy. If they want the help of government and society in protecting themselves, they must acknowledge that it is a quid pro quo, and honor their end of the agreement. Copy protected works will never truly enter the public domain; they are an effort to cheat the public. Such publishers are much more reprehensible than the pirates that prey upon them, IMO.

Similar arguments exist as to why software developers should be required, as a prerequisite to getting copyrights, to deposit a full, complete, and well-documented copy of the source code with the Library of Congress. (n.b. that this is NOT open source, merely 'disclosed' source.)

That reminds me of the alien-brain squeeze plot.

[hackwrench]

Where a person has been caused by some alien technology to soak up knowledge, and then goes to the aliens to get squeezed.
It's been a short story, an Outer limits story, Star trek TNG (Barclay), Stargate SG-1 (O'Neil)

Wrong URL

[MoonBuggy]

The url is http://mail.gnu.org/archive/html/discuss-gnuradio/ 2002-09/msg00025.html (no space before the 2002)

This is informative

[mrhandstand]

This has been covered here on Slashdot before. Some of the comments in the previous post are particularily informative.

Re:This is informative

[mrhandstand]

Nothing in the old article about HDTV, but loads about working hardware, future visions, etc. And some of the comment posters do a better job of explaining the methodology than anything that the current article had posted when I made the comment.

Re: This is informative

[Sunlighter]

It sure is. (snicker)

Question about Motorola's Digichiper II system

[Anonymous Coward]

The Canadian sattelite company, StarChoice, has receivers that are produced by Motorola and General Instruments. The encryption algorythm used to encode the video was produced by Motorola under the name "Digichiper II," which was a step up from the previous "Digichiper."

I am wondering, has anyone decoded the encryption process? As well, would I be able to decode the information via my TV tuner?

What, no link?

[Spunk]

Masturbate For Peace

Re:What, no link?

[pnatural]

Given your sig, it scares me that you knew about that site.

Re:What, no link?

[Spunk]

Look not to the sig but to the username!

Re:Top 5 reasons to process HDTV signals on your P

[Guppy06]

"# 5 -- You think a $3,500 computer with a 17 inch monitor is better than a $2,000 HDTV set with a 35 inch screen"

Compromise: Get a 35" HDTV with VGA inputs. Mmmmm...

"# 1 -- Record Cinemax skin flicks as part of the Masturbate For Peace campaign"

Screw that! There's gotta be Playboy/Spice decoders out there somewhere! :)

Slashcode adds spaces

[Anonymous Coward]

WhenYouHaveSoManyCharactersWithoutSpacesSlashcodeB reaksItUpToAvoidPageWideningPosts(amongOtherThings I'mSure).

Not his fault.

Hold on, I'm lost...

[Kaz Riprock]

How is different from network tv, where the scripts are rehashes of something from 10 or 20 years ago and you know the entire plot (painful jokes included) in the first two minutes.

Wait a second, are you talking about network tv or slashdot?

almost perfect...

[burns210]

Now all I need is an ascii version. Then I'll be all set.

Re:almost perfect...

[ProfMoriarty]

Well, you have to realize that GNUradio work for the construct of HDTV. There's way to much information to actually decode anything.

After a while you get used to it ... and all you see is blonde, brunette, redhead ...

Re:resolution

[linux11]

The following was taken from an online pdf file:

"The actual resolution of HDTV streams transmitted will usually be 1920x1088, because MPEG-2 requires the number of lines to be in multiples of 16 (1088 lines = 68 x 16)."

Also, keep in mind that the popular CRT and projection projection TVs will purposily overscan the picture such that some of the lines are pushed outside of the viewing area. So, while 1088 lines are broadcast, a projection TV may only show 1076 of them and clip 6 lines each from top and bottom. If overscanning results in only 4 lines being clipped then you will actually see only 1080 of the 1088 lines of MPEG-2 stream.

The width of 2730 pixels appears to be intended get close to the correct aspect ratio when displayed on a computer monitor. Based on how the people's heads look on my monitor, it seems to be a little over stretched. But when I return the images to 1920x1088, they clearly look squeezed.

20 Msample/sec

[wowbagger]

Actually, 20MHz isn't so bad - I work with 40 Msample/sec 12-bit flash converters, and there are 100 Msample/sec 12-bit flash converters on the market.

However, you DON'T build things like this with your brother's wood-burning kit and a old nail - These parts come in surface mount packages, and your board has to be carefully designed to maintain proper impedance matching on the RF traces, as well as having excellent grounding (RF and digital grounds meeting at one and only one point, ground planes cut as needed to prevent current loops, etc.).

Lastly, you need a proper dithering circuit to introduce noise equivelent to 1/2 of the least significant bit, in order to shape the quantization noise out of the frequencies of interest. Otherwise, you end up throwing away a couple of bits of resolution.

Those are the sorts of things you have top-notch RF designers laying out, and a top-notch fab build for you - either by having such a fab working for you, or by contracting it out.

Re:20 Msample/sec

[Compuser]

It is still dissapointing that they didn't design
their own board or didn't choose a better one.
If you look at their pix, you'll see lotsa crappy
coloring. I guess at least a part of that is due
to their 12-bit inputs. Their board uses AD9225 chip
for the actual A/D. It would be nice to use a
better chip (16-bit or higher), like e.g. AD1377.

Re:20 Msample/sec

[Compuser]

If they wanted to go commercial, they could
for example use SMT356 board from sundance.
Granted it is only 14 bits but that's
better than what they chose anyway, and I am
sure 10 MSPS 16-bit boards are available, you
might have to look for more than 5 minutes tho.

Re:20 Msample/sec

[GoRK]

Not that having a higher samplerate would not benefit them, but keep in mind that their HDTV implementation is getting them a datastream that's just as good as they can pull off-air. The color information is encoded in the MPEG data. The poor colors you see on their screenshots are JPEG artifacts. Pull up one of those 4MB .PNG's and you'll see what I mean.

Re:20 Msample/sec

[Maxwell]

A 100Mbits 12bits on a PCI card? In your PC?

Certainly faster sample rates are avaialable, and are often controlled by a PC, but this thing actually takes up a PCI slot IN your PC. I still say "wow" to that!

JON

Re:20 Msample/sec

[wowbagger]

Well, I meant that 100 MSample/sec flash converter chips are available, not so much that they are available on cards.

However, I have seen "'scope on a card" cards that would do over a gigasample per second for a short period of time. Obviously you don't stream that kind of bandwidth to across PCI.

(Hey Meirowsky!) Other possible sources for gear

[wowbagger]

I wonder if my buddy at Spectrum Signal Processing is reading this thread - perhaps they might be able to release a slightly lower cost solution to this.

Or not.

Hey Meirowsky - You reading?

OK Then...

[bombdotcom]

Come up with your own set of software projects that change the world as we know it and you can name it *anything* you want.

More info on software-defined radio

[Crusty Oldman]

A great site for software-defined radio:

www.nitehawk.com/sm5bsz/linuxdsp/linroot.htm

Re:Cool

[packeteer]

HAHAHA BitTorrent is such a load of crap. What your saying is i should download another p2p app but this time i have no control over my own upload bandwidth. Your saying i should freely give away my measly ADSL connection to companies who are too greedy to buy their own bandwidth? What a load of crap. If you want warez there is a million better ways to do it. Why are you posting a warezing tutorial to slashdot? Why are you pimping out BitTorrent which is clearly an inferior way of warezing? If you really look into BitTorrent you will realize it is some shady scheme thats probably really just some trojan out to make a few people money off greedy warez kids.

What ever happened to IRC? Dont you know you can all the TV shows you want in plani divx format off USENET? Who wants to download files in a special format that need to be converted to a format that feels less like DRM already. Just download K++2.0.3 or a gntuella client and you can get all the TV shows you want.

I eralize i might be flammed and modded for going against BitTorrent. At first when i heard about it i waw exited as it seemed like a good idea. Using the power of p2p bandwidth to solve the internet's bandwidth needs seemed fine. As i looked into this more i got sceptical. At first it seemed like any other cool project that i would support. I later found lots of patenting and secretism over this program and "HiveCache", a failed project by the same programmer and a similar idea. I am fearful that BitTorrent will be helpful at first but once it has a solid base will sell out and take advantage of what was once a good service.

Re:(Hey Meirowsky!) Other possible sources for gea

[psyconaut]

Whaddya mean? The card they used is only about US$1300 ;-)

-psy

Very flexible software

[LoRdTAW]

This project isnt just for HDTV but any radio signal one can capture, convert and sample to extract data. This software could be used as an XM radio or possibly a digital cable descrambler. All you need is a decent A/D card (one that can handle the bandwidth of the signal you wish to decode) and associated tuning circuitry. All the signal processing is done on the computers CPU. With SMP boxes, x86-64 and other CPU technology on the horizon the possibilities of building software recievers for most any digital signal is definatly something worth looking into.

Another thing people have to realize is that its just a reciever, the digital stream has to be decoded by another program making it perfectly legal. The program that might have to crack encryption or remove/ignore copy protect bits to record or view that data stream is what will be illegal.

Broadcast Flag Implementation

[YetAnotherName]

I hope so. An ideal implementation:

% gnutv --verbose --chan 13 --out alias.ts
Copyright 2003 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details, run gnutv --warranty
Capturing channel 13...
Writing MPEG transport stream to alias.ts...
Broadcast flag detected and ignored...
Recording...

Re:okay...

[packeteer]

In a nutshell that is one thing you CAN DO but thats not all of what gnu/radio does. Basically it is a program similar to airsnort or something like that which reformats a captured stream. The capture card they used to get HDTV is about $1500 but the program can be used for a lot else. It will take all kinds of incoming analog streams and put them into a nice digital format minus the copy-protection (a la macrovision) that came with it. The program is really great and now i want a bitching video capture card to make my own home tivo.

HDTV is useless for me

[Anonymous Coward]

Its size makes it impractical for anything like a Tivo. Until I can either get a realtime MPEG-4 encoder to compress these streams or get the data on the next DVDs its unlikely I'll be seeing any HDTV on my computer in the near future. I can barely afford to process and store all my regular NTSC video. Can you imagine how long it would take to compress a 2-pass 1280x1024 2-hour movie into an xvid/ogg file?

Re:HDTV is useless for me

[Powercntrl]

Can you imagine how long it would take to compress a 2-pass 1280x1024 2-hour movie into an xvid/ogg file?

I'd be more interested in how long it takes to downsample to a lower resolution before compressing it with XviD... Most of the DVD rips^H^H^H^H backups I do are downsampled a bit to sacrifice resolution for clarity.

HDTV at HDTV resolutions does look incredible, but I'm willing to tolerate lower resolution captures. If you consider how bad VHS is compared to a clean NTSC resolution stream (such as from a progressive scan DVD player), it's obvious the general public is willing to accept a recording solution that capures less than the broadcast resolution.

get this straight...

[Subnirvana337]

let me see if i understand this correctly...

they can intercept HDTV signals without the expensive set-top box...but what is stopping them from recording it? its copywritten material, but is it being released into public domain?

Re:get this straight...

[Wesley Felter]

You're allowed to record TV since it supposedly exists for the public benefit.

Re:get this straight...

[TheRealStyro]

bwahahaha... TV exists for the public benefit - good one there. Too funny. Ok, on to the real issue...

Actually this event could very well be brought under the law that prosecutes illegal cable TV 'descramblers' (not to mention that damn DMCA nonsense). Just because the signal is being broadcast, and you are able to receive it, and you have figured out how to process it, does not give you the 'right' to view and/or record it (or something like that (IANAL damit!)).

Personally, I think this is very cool. I will be looking into trying something like this when/if I get my *nix box back running.
Power to the people!

Re:get this straight...

[Wesley Felter]

Actually this event could very well be brought under the law that prosecutes illegal cable TV 'descramblers' (not to mention that damn DMCA nonsense). Just because the signal is being broadcast, and you are able to receive it, and you have figured out how to process it, does not give you the 'right' to view and/or record it (or something like that...)

I think the laws are different for broadcast, cable, and satellite TV. You can watch broadcast HDTV for free with a TV, so what's the difference in watching it for free with a computer? You can record broadcast HDTV with a HD-VCR, so what's the difference in recording it with a computer?

12 bits isn't the limiting factor

[wowbagger]

The 12 bits in the RX is not really the limiting factor.

A 12 bit A/D raises your quantization noise, but the quantization noise is at the sampling frequency - you can "shape" the noise away from the signal of interest, and gain bits as you process the signal.

This is the trick that the 1 bit D/A sections in modern CD players use - the D/A is only 1 bit, but running at a very high rate (1MHz or more). As a result, the quantization noise is all above the audio band, and the system has the low-frequency resolution of a 16 bit system.

Think of it as dithering - really, that is what it is.

Re:12 bits isn't the limiting factor

[Compuser]

Ok, fine, but then why are their stills so
crappy? I mean look at those color blotches.
Is there any reason for that or is that the
best HDTV can get?

Re:12 bits isn't the limiting factor

[wowbagger]

I don't know - it could be that their receiver section has a lot of phase noise, or isn't very linear, or is trying to AGC the signal, or isn't quite wide enough, or isn't very flat through the IF passband.

They may also not have the strongest signal to recover, and are getting a high bit error rate.

They may also have a bug in their forward error correction routines (or not have ANY FEC).

They may not be feeding an optimal level into their A/D converter, so they are not using the full range.

Re:12 bits isn't the limiting factor

[Anonymous Coward]

I don't know what's wrong with their captures, but they're completely fucked up. The resolution is wrong, the color is off.... all in all, it looks like most GNU software. It sounds good until you try to use it.

Re:12 bits isn't the limiting factor

[i_am_nitrogen]

It says on the site that they used GIMP's auto color balancing to adjust the snapshots. That will mess up the colors pretty quickly. Someone else posted a link that has some ads in HDTV .ts format (MPEG-2 transport stream), 1280x720. Take a look at those. I've yet to find a media player capable of playing them, though. VLC screws up the sound, Xine plays the video choppy, MPlayer doesn't support transport streams.

Re:Top 5 reasons to process HDTV signals on your P

[evilviper]

# 5 -- You think a $3,500 computer with a 17 inch monitor is better than a $2,000 HDTV set with a 35 inch screen

Why a $3,500 computer? At Walmart, a 1.1GHz Duron-based PC is $200. Besides, an HDTV set can't record, time-shift, re-encode to DivX, etc.

Re:Top 5 reasons to process HDTV signals on your P

[Ymerej]

Does the $3,500 include the $1,300 cost of the Measurement Computing PCI-DAS4020/12 20

Re:TV doesn't challenge me

[Forkenhoppen]

If you had a TV, I'd recommend you check out The Daily Show. Its informative, insightful, and funny. Although, yes, it is kind of a news show.. ..So I take it you're not a Buffy fan? :)

MOD PARENT UP!

[nuntius]

The "Pot of Gold" was great...

so much Latin slap-stick to choose from...

good memories...

But wait, now what would you pay?

[frovingslosh]

Well, for $1299 you only get an A to D board. But a pretty important part of a GNU software radio project is a digitally controlable tuner that can feed this board. This thing can't convert from the R/F directly, you need a tuner to get the signal down to a low enough frequency range that the $1299 board can deal with it. In addition, the tuner must output a suitable singal that the board can use and it must be tuneable over a wide enough range of input frequencies to be worthwile. What does it really cost to play with GNU radio? This $1299 board doesn't really get you in the door!

Re:But wait, now what would you pay?

[mlyle]

You don't really need a $1299 A/D board if you want to start playing with GNU Radio, unless you want to decode a high bandwidth signal like HDTV.

For a couple hundred bucks, you can get an A/D board up to a couple hundred kilohertz, and then hook it up to the IF of any cheap old radio you have sitting around.

Re:Rough Explanation-Bring enought for everyone?

[linux11]

The majority of the rest of the world is not connected to network backbones that support multicast. Also, ATSC can carry MPEG-2 streams with a maxium burst of around 19.2Mbps. For a 100Mbps network or even a 55Mbps wireless, this isn't much of a limitation to retransmittion. But for most DSL/cable connections this limitation will keep retransmittion from ever occuring real-time without re-encoding.

What's it's good for...

[vrmlguy]

I've seen several postings asking, "So what is GNUradio good for?" Here's why I'd want one.

I've got a PVR; I leave it on all the time so when I walk into the room and I'm interested in what's on, I can rewind and watch it from the beginning. Unfortunately, that only works for the one channel that the PVR is tuned to. If I change the channel and see something interesting, I can't rewind it. What I want is is PVR that records the last hour or two of every channel that I get.

GNUradio is the receiver for that PVR. The PVR records the unfiltered signal from the antenna. That gives you all the channels at once. When you want to watch a show, the GNUradio software reads the raw data and filters out the channel you want. If a show looks interesting, you can rewind and watch it from the beginning. Even if there are two or more interesting shows on at the same time, you can filter them both in parallel and re-record one or more while watching another.

Re:What's it's good for...

[flux]

Better be prepared to buy some heavy storage equipment then too, you need 2.5 terabytes to store days worth of signal.. (Assuming the maximum sample-rate of the card, 20Msamples/second, 12 bits per sample.)

Re:What's it's good for...

[tweakt]

Sounds very ambitious. Assuming you had the computing power to decode in real time 2 HDTV channels it would only use roughly 4.5GB/hr (20Mbit/s/channel). Given the size of today's hardrives, that's not nearly a problem.
(Note: I'm not 100% on the bitrate, I'v e seen from 20-40Mbit, so YMMV)

That's equivelant functionality to today's PVR systems for satellite receivers. Whether you want to add the ability to decode and save more channels simultaneously, is simply problem of computing power.

Re:What's it's good for...

[topham]

Take the datastream required for 1 channel for 1 minute, multiply by the number of channels.

Lets see, an 80Hr TIVO is an 80G harddrive and stores 80hrs (aprox) at the worst video setting. For simplicity we will assume 1Gigabyte per hour. (A little off since an 80hr tivo has less than 80gigabytes of storage for tv programs.. but close enough).

So, 1 minute of video for 1 channel is 16Megabytes. So, 1 minute of 60 channels is 1Gigabyte, and you want atleast 30 minutes of all channels, so 30Gigabytes.

Assuming you have the bandwidth to/from the harddrive to shove 30Gigabytes of data to it in 30 minutes without dropping a frame your set.. doubt you'll actually have any bandwidth to read back a data stream from that though.

(Oh, and no, you can't store the datastream in LESS space as you would then be losing parts of the datastream. You also couldn't compress the RF data using a lossy algorithm as you'd lose necessary data. So, you'd either have to store the entire datastream and compress with it a lossless compression algorithm or recover the 60 datastreams and store them. Its likely the 60 data streams combined would be LESS storage than even a compressed full datastream...

Oh well, a few years down the road...

Re:What's it's good for...

[Sloppy]

So, in other words, you need a $100 drive a few years from now. Ho hum.

369 Reps

[smiff]

how many reps in DC do you think they already have under their evil greenback spell?

Since you asked, 369 Representatives. They also have 80 Senators for a total of 449 congresscritters. That's 84% of congress.

Re:369 Reps

[robmx]

I had no idea Congress was so inexpensive. Under $7 million.

Transmit cost: a lot more

[i_am_nitrogen]

The gnuradio package does include an atsc_tx signal modulator, but I don't know what kind of hardware is necessary to actually get the signal in the air. Transmitting is probably just the reverse of receiving, so you're probably looking at a 20MHz ADC, some way to modulate the carrier, then remove it so that only the sidebands remain (an 8VSB signal modulator - did I get that right?), a 50-1000MHz multiple kilowatt amplifier, and an antenna.

I have no idea what any of that would cost, but if I had to make a guess, I'd say that you could have pirate GNU Radio-powered HDTV for not more than a million dollars or so.

Mod parent up.....

[Odinson]

Mod parent up.

"and act as an 802.11 card to boot"

There is a company in my lug looking to rig sevral 802.11 cards into a wap for a cheap toaster firewall/router type thingy.

There is a FCC unregulated application for such a (two way) D/A card and transmiter/reciever. EE geeks you should be scott free from hollywood evil accusations.

Re:Cool

[Thing 1]

Just download K++2.0.3 or a gntuella client and you can get all the TV shows you want.

Thanks for the info. I've only used BitTorrent a few times (last Sunday my ReplayTV didn't record the 300th Simpsons for some reason, so I was able to get it from the Internet and was happy with BitTorrent even though multiple instances blue-screen my Windows 2000 box).

I didn't realize it had these problems. I've never used IRC or Usenet to get binaries. And as far as special formats, the shows I've gotten from BitTorrent have been in .mpg or .avi format, I didn't need to do any conversion.

From what I've read there are upload-restricted clients available but I haven't investigated them. I will look into K++ though. Thanks! (Here's a link -- K++ is KaZaA Lite.)

Calculus is one sexy and powerful bitch.

[BigBlockMopar]

Where do I learn more about this, other than the obvious BS in EE option?

Do your math homework... and if you're not in school, just pick up, read, and do the exercises in a bunch of good calculus and linear algebra textbooks. (The key is to actually *DO* the exercises, math is not a spectator sport!) If you've been away from it for a while, I recommend Sylvanus Thompson's 1910 classic, Calculus Made Easy. Chapter 1 is titled, "To Deliver You From The Preliminary Terrors". The book is still in print.

Calculus sounds terrifying, and most people think of it as a weed-out course. But if you do the exercises, any idiot can get an A+ in it. Only the intelligent see the sheer beauty and elegance of Newton and Leibniz' greatest contribution to the world. And you'll find yourself using it everywhere - calculus is the mathematical equivalent to the speedometer in your car. You could calculate your speed by looking at the odometer and your watch, but the speedometer essentially takes the derivative (finds the rate of change) of your position.

Most of these modulation techniques are based on the mathematical manipulation of sinewaves. You have to have a good understanding of trigonometry, complex numbers and multivariable calculus. Then, Fourier is your Big Friend In High Places.

With the mathematical basis in place, the modulation schemes themselves might be best left to a math degree rather than an EE - though, in my program, the double-degree was only a two credit option.

(Bachelor of Mathematics is also fun; mathematicians are almost always crazy, and it's really great to see how frightened or awestruck Joe Public gets by someone who has a degree in math. Even with "just" the iron ring, you can tap it incessantly on the boardroom table every time the boss says something stupid.)

And I have to tell you - I can't say that I understood all of what the original poster said - I didn't. I stick with EM and power more than the rather abstract modern modulation systems.

"I've balanced the budget for you, but I had to take the square root of a negative number to do it."

- Quoted by memory from Dilbert cartoon e-mailed to me after I described an incident where a friend of mine *actually did that* to our former boss.

Set-top HDTV Receiver which outputs VGA?

[BigBlockMopar]

Sounds too useful to exist.

Here's something I'd like to find, but I haven't been shopping around yet, and I don't know whether it's available or not. I'm also in Canada, and we've been a little slower to adopt HDTV up here, so I can't walk into Future Shop and browse with the same number of products available.

I really have little use for large TV sets.

On the other hand, VGA monitors capable of doing 2,000 horizontal pixels must already be available somewhere - not that I've been shopping for one of those, either. Either way, I still expect it would be cheaper than a 16:9 HDTV monitor.

Anyone know of any set-top boxes which receive HDTV and output letterboxed VGA video, either in the same resolution or down-converted to a popular VGA resolution?

Re:Set-top HDTV Receiver which outputs VGA?

[Anonymous Coward]

Well, in Australia you can get the DGTEC DH-2000A that supports VGA output.

Correction to Above

[Sunlighter]

I meant to title the above comment

This is informative (Score:5, Informative)

because that's what I saw. But Slashdot chopped off my parenthetical. Had I but pressed Preview, I could have used hyphens instead and that would have worked. Darn.

The MPAA's Reaction

[sconeu]

See! We told Congress that everyone is an Evil Content Pirate(tm), but you guys wouldn't believe us! We need that Fritz Chip yesterday!

Re:Cool

[packeteer]

KaZaA Lite is a really good program but can be abused too easy. It lets you "cheat" with the system so that you can be a bandwidth hogging leech if you really want. I find its useful for when i need to locate a file that otherwise i would be blocked from downloading becuase of ratios. This does not mean i am a leech. K++ lets me find files that are hard to get which i then share openly to others. I know that if i were to not share to p2p then im doing my part in killing something which i would like to use again.

So despite KaZaA's drawbacks of being abusable i still think it is better than BitTorrent which sounds like abuse waiting to happen to me.

Re:Is CD cover art illeagle?

[JThundley]

Everyone's a comedian...

Re:I'll name it Windows!

[More Karma Than God]

Hmmph. This reminds me of why I had resolved to never try to post anything funny on Slashdot.

Here's an idea. Create a checkbox in the post comment page for "Funny". Only moderators who have proven they have a sense of humor can mod a "Funny" post down. Of course if a "Funny" post is modded down it should be a 4X karma hit.

See, now this is genuinly offtopic. Come and get me moderators!

More info on Software Radio

[fygment]

Can be found here:

http://www.ettus.com/sdr/sdr_w6yx.pdf

Apex will have a lot of orders for hardware....

[MicklePickle]

You can buy the hardware from here

Hey Russ Smith

[SubtleNuance]

Go fuck yourself.

Im proof that the left can have just-as-much vitrol and anger as you smug plutocratic cheerleaders.

Again, Fuck-you Russ Smith.

Nope

[Andy Dodd]

I think I heard something like 40x realtime.

As in 1 minute of HDTV will take 40 minutes to display.