Slashdot Mirror
Could CDRW Disks Replace Videotapes?
NewtonsLaw asks: "I'm in the process of building a TiVo-like PC that uses off-the-shelf technology to implement video timeshift, MPEG recording, MP3 recording, etc along with Net-radio functionality. Over the past two months I've effectively replaced VHS video tapes with CDRW disks. Once a program has been captured on the PC in (S)VCD MPEG format, I can either watch it by playing back the recorded file or dump it onto a CDRW and watch it on my DVD player, before blanking the disk and returning it to the 'empty' pile. What I've noticed is that most of the CDRWs I've tried only last about 30-40 rewrites before they start showing significant data dropouts (almost always at the start of a recording). Since disks in (S)VCD format don't carry the same level of error-checking/correction as disks written in regular data format, such dropouts are more noticeable than they would otherwise be (of course the up-side is that you get to store 805MB on a 700MB CDR/RW without overburn).
What I want to know is -- how many rewrites do most people expect from their CDRW media? I seem to recall seeing a figure of a thousand rewrite cycles being touted by some manufacturers. Is this realistic? Thirty rewrites makes a $2.50 RW disk an economic medium for this purpose but it seems a hell of a long way short of 1,000."
"I've tried CDRW disks from several manufacturers and they're being used in a new Sony CDRW drive which seems to function just fine. I've also encountered a slightly shorter lifetime for CDRW media when used for (S)VCD disks and written by a slightly older HP CDR/RW drive.
And before anyone asks 'Why don't you just play directly from the HD?', I should point out that I have to share the TV gear in this house with the rest of the family so it's just easier to burn their stuff to disk and let them use the DVD player than to fight over access to the TiVo-clone."
If I remember correctly, the CD-RW blanks I have at home (14x compatable) say they are "guaranteed" for 100 re-writes.
Also, what speed are you burning on these CD-RW's at? Maybe you should try lowering the recording speed and seeing if you still get the drop outs.
Not All Who Wander Are Lost
Typicly I will reuse my CDRW disks arround 10 -> 15 time, but im storeing my programs, mp3 backups, and web dev work... so once its backed up to my satisfaction... I stop...
:)
Personaly I think that to acheve 30 -40 rewrites to a VCD disk with no real loss in quality beats the shit out of a VCR which you only really get 4-5 rewrites out of before you start noticeing quality issues...
Keep up the good work, and keep us informed as to when we can buy the set top version of your system
The Code Ninja is swift with his tool, precise in his delivery, and deadly accurate in his execution.
One of the small-town grocery stores nearby actually sells CD-Rs and CD-RWs at pretty decent prices, and place them next to the blank VHS tapes in the store. Seeing as to how they're becoming more ubiquitous, and devices like the Terapin VCD Recorder (at http://www.thinkgeek.com/electronics/video/57a6/) are starting to appear, perhaps CD-RWs could give VHS a run for its money, with comparable video and audio quality, as well as interoperability with a computer. For instance, you just missed Everybody Loves Raymond, so you hit KaZaA and somebody uploaded a VCD for you. So yeah, they've got their merits.
-
And the Angel said unto me, "These are the cries of the carrots! The cries of the carrots!"
Because it's hard to play a hard drive in a DVD player.
Figure $5 for a pack of 50, so $0.10 each -- you can't re-record on them, but it shouldn't cost you more than CD-RWs that start failig at 15 uses or so. Plus, this way you have the ability to create instant archives of your favorite shows, or just discard the used disks.
The CDR will never replace vidoetapes for the same reason HDTV is only just starting to bloom and cassette tapes were EVER on the market.
People don't care about quality! If people cared about quality Microsoft would be out of business, Airlines would have decalred bankupcy years ago, and NO ONE would eat fast food.
Unfortuately people care about how little effort they have to excert to get something done. People don't want to deal with CD-R's because, despite an overall decrease in effort required, short term effects are minimal.
On a side note: CDRs would be a great alternative to video tapes. Tape media sucks
Help I'm a rock.
storing video on punch cards. This would be great for editing as I could just pull out a stack of cards and insert it into another stack.
Has anyone else done this?
Answering your question would be a violation of the DMCA. Sorry, ask Jack and Hillary.
"Eve of Destruction", it's not just for old hippies anymore...
This is an ongoing discussion at Plasma. People with the bucks have been contemplating this for a while. Be sure to read up on the forums for the technical details as well. More info here.
Please note there are solutions that require money. How cheap are you going to be?
If we don't fight for ourselves no one will.
Insert disk and hit record, for a price point of $200.00 when it is in volume. And 2.40 for a CDRW?!? Just jump to DVD(+-) RW. They are only $6.00, and getting cheaper, and would hold about as much as a long video cassette at similiar quality. Also, tapes are not reliable either. They are only good for about 100 plays.
The law is a weapon of the government, not a protection for the likes of you. Surely you understand that.
Are you sure the discs are not getting dirty w/fingerprints, dust, etc.? Such things can cause a lot of the problems misattributed to media failure...
You should take a look at the GNU version of TiVo called GnuVo. It's pretty nice except it won't let you watch any shows about capitalism.
A good place to learn how to convert various media to burnable (S)VCD format can be found at http://www.vcdhelp.com
I don't doubt the quoted figures of "1000 rewrites" for CD-RW media, for the reason that the crystalline substrate which stores the data proper should last around that much, chemically. In my experience, it's the physical disc which fails- scratches from handling, pitting on the reflective aluminum layer, etc.
CD-RWs reflect around 25% of the read laser, as opposed to CD-Rs which reflect around 75%, and pressed CDs which reflect close to 100%. When the signal-to-noise ratio is this low, the A/D circuitry has a hard time keeping up even with minor defects- fingerprints and dust are much more deadly on a CD-RW than on a CD-R.
In my experience, the first burn to a virgin CD-RW delivers CD-R-like readability, but once you rewrite it even once, the drive has to work a lot harder. I used to treat my CD-RWs like floppies, carrying them between the lab and my home, playing with them while waiting for an operation to complete, etc. and got maybe 4-5 rewrites on average. I then started keeping them inside jewel cases at all times, exposing them for a few seconds to put into the drive, and immediately got 20+ rewrites out of them.
Also, we were using really bad drives at the lab (some early HP CD-RW burners which often rejected discs) and when we upgraded the machines (to better HP burners, in late 2001) rewritability literally doubled for me to about 40+ rewrites. So the type of drive makes a difference as well IMHO.
Wrists killing you? Not in 2 weeks. Learn Dvorak.
most of the CDRWs I've tried only last about 30-40 rewrites before they start showing significant data dropouts (almost always at the start of a recording)
Sounds like you've reproduced the VHS experience accurately.
Karma: Good (despite my invention of the Karma: sig)
how many rewrites do most people expect from their CDRW media
Zero. Actually, I find that CDRW are actually CDW. I can write to them, but I never expect to be able to read back from them. I've tried on dozens of CDRW drives, and I've never had luck archiving for a month or more on CDRW. Sure, "most" of the time it works - but it falls far short of my expected success ratios.
I've learned not to trust CDRW. I always use CDR instead.
Education is the silver bullet.
The one exception I can see to this is if you're using the CD as a data transport mechanism, between your PC in the office with the fast data connection and your DVD player in the living room.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
Unless your device supports capturing of original closed captioning information onto the CD-RW's - meaning you preserve the information present including the stuff in the vertical blank interval and replay it on playback - you will never be allowed to bring this device to market as a consumer VCR replacement. As far as I know the SVCD format does not have any built in mechanism for this. There are certain things you need to do to meet FCC requirements before this device will be allowed to be sold in the USA market. Same rules applies to closed captioning decoders being required in all TV's 13" or larger.
Ah, but there really is a TiVo clone in the works: FreeVo.
The roots of education are bitter, but the fruit is sweet.
--Aristotle
And yes, I've written and pointed this out to my reps. :-)
When companies talk about MTBF, or number of re-writes, or anything like that you have to remember these few rules:
1. They were done under ideal conditions and not your normal, everyday, household conditions.
2. They count every time they were actually able to do whatever. (Like in being able to write to the CDRW disk they will count even partial writes in order to boost their numbers.)
3. They don't care if they make outrageous statements. It takes a very long time to prove them otherwise. (Take the cigarette industry - PLEASE! Look how long it's taken to prove them wrong. [And they are STILL fighting it in the courts.])
It used to be that if you cut whatever the company said in half you could be close to what the actual figures were. Now it's about a tenth of what they say. Not that all companies are like this. But there are quite a few.
Someone put a black hole in my pocket and now I'm broke.
Wow... amazing how people don't get it.
If it's on a CD in SVCD format then you can take it to nearly any DVD player, stick it in, and watch. That's it.
If you're limited to a computer then you're paying 4-10x the money for the playback device and you can't transport it. Want to record something for someone else, or to take to a friend's house and watch? Too bad. Want to send a recording of an important TV show to family or friends? Nope. Can't do.
Not to mention that labeling a CD as "Junkyard Wars, Season 5, Episode 3" makes it a whole lot easier for a non-techie to deal with than some obscure location on a poorly integrated HTPC.
Here are my notes about how I made one disc:
I wondered if I got some quality degradation by exporting from MA in motion-JPEG format, rather than keeping it in native DV format, and then encoding to MPEG. Ideally some of the JPEG frames would just directly become keyframes in the MPEG output; but in this case I was scaling too, so that's not possible. Anyway most of the output formats in MainActor for Linux have bugs, and MJPEG happened to work well.
I'm the guy who posted the story and I'm documenting my experiences and the project at aardvark.co.nz/pvr/.
:-)
What you say has some merit -- SVCD is certainly streets ahead of VCD in terms of image quality.
However, DivX is not quite the ogre you make it out to be.
For a start, it takes no more CPU to encode DivX format as it does to do a *good* job of multi-pass MPEG encoding.
On a 1.8GHz P4, TMPGenc takes around 6-8 hours to encode a 100 minute movie into an MPEG2 file to SVCD standards using multipass variable-bit-rate encoding.
You can get faster multi-pass MPEG2 encoders but they are *expensive* -- TMPGEnc is free for MPEG1 encoding and costs (from memory) just $49 for the version with MPEG2 capabilities.
By comparison, the same machine usually does a multi-pass DivX encoding in just a fraction that time.
In respect to playback, the DivX codec is quite nice insomuch as it allows some optimizations and post-processing to be performed as the video is played. This means you can create a video file that is able to be played back on a variety of different machines with different CPU-powers -- such that the faster machine will produce a better result but the slower machine will still play without pauses or stuttering.
In the past couple of months I've downloaded and evaluated hundreds of MB of applications, drivers, documentation, etc for all manner of commercial and freeware PVR solutions. These will all be compared on my site shortly.
I'm also about to publish my findings on the Haupaugge PVR card which does hardware-based MPEG1 and MPEG2 encoding -- thus freeing up the PC's CPU and allowing more "headroom". This is important when you're trying to do things such as timeshift or concurrent record/playback.
Linux-based software solutions are also being evaluated but unfortunately (damn it!) there are only two or three that appear to have much merit.
Given Microsoft's agenda to hog-tie all video and audio with DRM I'd really like to come up with a Linux based (and preferably OSS) option that is reliable, functional and ergonomic.
The truth will (eventually) be revealed
Try this link.
;-)
I'm planning to update the site with all my latest findings later this week -- including a review of a Haupaugge tuner/capture card that has onboard hardware MPEG1/MPEG2 encoding.
Linux-based options are also being reviewed as I type this
Why are you using re-writes at all? You can get a spindle of CDR's nowadays for $16.00 CDN on sale. (Must be $10 US?) That's 10 cents a disc, and you get to *keep* them. You are meanwhile spending 2.50 on a CDRW that you say can only be burnt 30 times, or 8.3 cents a burn. Seems to be it just isn't economical at all, when you could be spending pretty much the exact same amount and archiving all yoru movies instead of wiping them.