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BBC Lowers HDTV Bitrate; Users Notice
aws910 writes "According to an article on the BBC website, BBC HD lowered the bitrate of their broadcasts by almost 50% and are surprised that users noticed. From the article: 'The replacement encoders work at a bitrate of 9.7Mbps (megabits per second), while their predecessors worked at 16Mbps, the standard for other broadcasters.' The BBC claims 'We did extensive testing on the new encoders which showed that they could produce pictures at the same or even better quality than the old encoders ...' I got a good laugh off of this, but is it really possible to get better quality from a lower bitrate?"
...of blind retards.
THL phish sticks
They also lowered their math standards. From 16MBps to 9.7 MBps is a 40% reduction, not "almost 50%".
I've abandoned my search for truth; now I'm just looking for some useful delusions.
Yes, if more time and passes are spent encoding the video, lower bitrate CAN result in a higher quality video. However, this does not appear to be the case in this instance.
Benny Hill is awesome! Especially when he runs around really fast.
Sure, if you also switch to a better codec, such as using H.264 instead of MPEG-2. However, I don't think that's what's happening in this case.
So they starting to act like comcast cable with there compressed HD.
but is it really possible to get better quality from a lower bitrate?
If you are changing the compression algorithm of course it is possible. In H264, there are a lot of compression possibilities which are not used by the compression algorithm but which will be recognized by the decompression algorithm.
Any lossy compression works by throwing away bits of the picture that the viewer might not notice. You can lower the bitrate with better psychovisual and psychoacoustic models. You're still throwing away more information, but you're doing it in a way that the user is less likely to notice. This takes more CPU time on the compressor, a more optimised encoder, or a better algorithm.
I am TheRaven on Soylent News
Ever looked at mpeg2 vs h264? That's not what happened here, but your question gets a huge Yes anyway.
It's not impossible to get better results out of lower bitrates, but you have to pay the penalty elsewhere, typically in encode/decode complexity.
If your decode hardware is fixed (it's generic HDTV hardware), then there is much less room for improvement, and half the bitrate is an enormous drop. It's no surprise that the BBC viewers complained.
I read the internet for the articles.
Nitpick: So 39% is "almost 50%"?? I would have called that "almost 40%". Then again that is a /. summary.
After logging in slashdot still does not take you back to the page you were on. It's been that way for 20 years.
They just remove the naughty bits.
Bitrate is only part of the equation -- the H.264 spec allows for a number of different ways to compress video, and it's up to the encoder to find out which is best for your video. Even in the same encoder, you can tweak dozens of settings in ways that dramatically change output quality -- usually a trade off between time and size.
x264 has beat every commercial encoder out there -- in some cases, on a level that would indeed render higher quality with half the bitrate.
Compression is just the discarding of irrelevant or less relevant information. With images or video, that means keeping the perceptually meaningful content and discarding the rest. An improvement might come about if the encoder was removing irrelevant variations (noise), or smoothing out unnecessary details away from perceptually salient objects (making them easier to see).
It's pretty hard to make an image encoder that maintains the important perceptual qualities of every possible image, so IF their encoder is good, maybe they just didn't test it on the whole range of stuff they eventually used it on.
is it really possible to get better quality from a lower bitrate?
It is, if your original encoders sucked...
"We did extensive testing on the new encoders which showed that they could produce pictures at the same or even better quality than the old encoders"
I find this hard to believe, especially as there are already complaints in the iPlayer forum.
Lower bit rates can reduce noise if it's of the high frequency, snap, crackle, pop variety. You get less information but it's more soothing. Some people prefer lower quality to higher quality because the high frequency stuff is annoying. One of the nice advantages of getting older is that they can really scrimp on quality and you can no longer tell the difference.
I'm far from an expert, but my understanding is that to a limited extent, you can make a trade-off between the bitrate and encoding/decoding time. H.264/MPEG-4 AVC is superior to older codecs, generally having both better visual quality and a lower bitrate, but it requires much more time to encode and requires more powerful hardware to decode the stream.
But my very loose understanding is that all they did was lower the bitrate and maybe conducted a test to see if some random idiots could tell the difference with ideal samples.
Try watching a football game here in the US and you will see what crap quality can be. The turf turns into squares of blur when the camera moves, then returns to blades of grass when the picture is stationary. As soon as you spot it you will hate it. If you don't see it then OK for you.
I used to have a friend who could spot the two little circles in the top right of a movie in the theater telling the projectionist to change the reel. Once he saw them the movies were never the same again.
If you're watching a soap opera, you only need to see a few frames per week to follow the story. If you are watching a live sports event with a lot of action, most people will notice every dropped frame and compression artifact (I've noticed myself while watching the Olympics via satellite feed.) Methinks they did the testing on a relatively static video. Video compression works by (among other methods) creating a key frame, then sending diffs off that key frame for several frames. If every frame is completely different, compression does not work well.
I've abandoned my search for truth; now I'm just looking for some useful delusions.
For reference, the BBC HD content on iPlayer is 3.5Mb/s for 720p (no higher quality available). 9.7Mb/s is less than three times as much, so it probably won't be long before the streaming and broadcast signals are the same quality.
I am TheRaven on Soylent News
BBC accountant: We provide the $ame or better picture quality with half the bitrate! Just think of the $aving$!
BBC IT decision maker: I $ee what you're $aying.... The$e picture$ look $uper!
Public: This looks like crap.
BBC rep: (waves hand) The$e aren't the compre$$ion artifact$ you're looking for. We can go about our bu$ine$$. There are no complaint$.
http://xkcd.com/598/
Don't quote me on this.
If they've switched from MPEG-2 to MPEG-4, then yes, you can get equal or better quality at a lower bitrate.
https://www.eff.org/https-everywhere
was the featureless black-screen video to 4'33" from John Cage. Results were far better at the lower bitrate. The absolute darkness was less blurry.
Nullius in verba
The article talks about bitrate, which implies not a change in codec, so it remains mpeg-2. I'm assuming the BBC is available OTA, so unless they want everyone with a HD ready TV to have to get a new receiver box they can't just change to x264, etc. So in this context, the answer is no, using the same codec at a reduced bitrate can't produce better than the source. However, that assumes you are comparing to the original source. Take for example a standard DVD player which has a mpeg2 uncompressed file at 480i. The resulting image on a very large 60+" HD TV may appear blocky in some situations. A good DVD player will be able to interpolate and massage things around so that the resulting 1080i image on your screen indeed does look better on your screen. Although the image itself may be quite a bit different than the original pure source. So you have a perceived better frame image, although it may be quite a bit changed from the source.
Just look at carbon... carbon alone without any compression isn't quite nice... ;)
But COMPRESS it and you have something much higher in quality......
Is she saying that they've optimized their HD for people without HD screens, or am I just confused?
It really does sound like they're trying to sell something which isn't HD, but gets sold as if it is. Strange. "Now, to server you better, we are open fewer hours."
Cheers
Lost at C:>. Found at C.
Lossy compression formats depend on an understanding of human perception. Nobody has a perfect model of the human brain, and nobody has a perfect algorithm for deciding what data to keep and what data to throw away.
If you have a better model of human perception than your competitors, then your encoder will yield higher quality output. If you spend 50% of your bits on things that nobody will notice, and I spend 25% of my bits on things that nobody will notice, then my 650kbps stream is going to look better than your 900kbps stream.
LAME did not win out as the MP3 encoder of choice just because it is free. It won out because its psychoacoustic model yields better-sounding MP3s at 128kbps than its competitors managed at 160kbps or even 192kbps.
I'll toss FIOS under the bus too. Verizon's HD varies greatly. I'm not sure if its the channel companies themselves or Verizon doing it...
Either way, I hate watching fast motion movies or tv shows where the bitrate is too low.
Try watching "How its Made" on discovery HD and watch how compressed things look as fast moving manufactured parts pass through machinery.
Same for HBO films etc.
But then iPlayer appears to use H.264, which allows for more efficient encoding than the MPEG-2 codec used for digital TV broadcasts.
digital movie theaters don't have them and they have better video there as well.
Nothing to see here. Move along.
Oh, I'm sorry sir, I thought you were referring to me, Mr. Wensleydale.
16 -> 9.7?
Try almost almost 40%.
But yes, still a terrible thing to do.
The current encoders they use are trash.
Dark scene? ENJOY YOUR MAGENTA!
Fast scene? I HOPE YOU LIKE GREEN.
The pay HD movie channels have terrible encoding, for the most part. HBO HD, SHO HD and so on exhibit significant coding artifacts during high motion scenes. A notable exception appears to be HDnet Movies: they can faithfully reproduce all manner of complex and fast changing content; would be nice if the well-funded big-boys followed suit. Speculation is that the big-name networks utilize bandwidth-constrained HD feeds intentionally. The majority of their last-mile distribution partners (DBS satellite and terrestrial) are capacity limited. Not much use in sending 16Mbps MPEG2 HD signal to Comcast, if they recompress and statmux multiple channels together into an over-committed modulator. The FiOS guys have stated that they will not recompress any feeds they receive; they promise to deliver the full bandwidth that they get from their suppliers. HDnet Movies looks very clean. Wish the big movie guys would provide FiOS with higher-fidelity HD feeds to deliver.
I suspect the move is connected with Freeview (a non-profit organisation, of which BBC is a member, that runs the free digital broadcasts) and the digital switchover. The BBC are probably thinking that if they cut their HD bitrate there can be more HD channels (and I assume more people would be able to get a good-enough signal). Or it just costs less.
Try watching "How its Made" on discovery HD and watch how compressed things look as fast moving manufactured parts pass through machinery.
Well, there's your problem. Try watching The Woodwright's Shop on PBS. Things move a bit slower there.
Have gnu, will travel.
Sooo ... since "math" is shorthand for "arithmetic", is the plural "maths" shorthand for the plural "arithmetics"? Or perhaps it's shorthand for the broader category of "mathematics", in which case it's pluralizing "mathematicss"? "Mathematics's"? "Mathematics-es-es"? Technically speaking of course.
Posting as AC to avoid being lynched by a horde of angry nerdss. Or maybe be because I don't have an account. I forget which.
If you took that seriously, read it again. It's pretty obviously a joke.
And a brilliant troll.
The Head of Technology for BBC HD, Andy Quested, has posted extensively about HDTV transmission bitrates. If you want more info than a brief summary news article try http://www.bbc.co.uk/blogs/bbcinternet/andy_quested/
So what you're saying is although they tested it, they didn't test it. ;-)
Quack, quack.
Lets say I create a codec for broadcasts which contain totally random information at periodic intervals which will be ignored by my decoder. Now if I replace this random information with some more detail about the picture, but using less data than the random data that was injected in periodic intervals, theoretically I have produced better quality with lower bitrate!! Taking a more practical outlook, I am sure out of the many tens of codec and decoders that are used out there today, I am sure some codecs could be very smart in compressing video data with better quality at lower bitrate. So, its all in your codec and decoder!
When a thief sees a saint, all he sees are his pockets!
They didn't change thier codec, they are still using MPEG2. Here is the thing with MPEG, its a decode standard, not an encode standard. So, if you come up with some new novel way of encoding, as long as the format of the output stays the same, and the decoder undersands it, its not a problem.
To this end, MPEG2 (and 4) encoders have over the years become more efficient. What does efficent mean? Well with encoding you have 3 variables, output quality, bit rate, and processing power. Pick 2, or really pick 1. If you want a better bit rate, reduce qaulity, or increase processing power, or do both. But there are limits.
Now taking HD which in the US was originally designed to be 19.8 Mbs down to 9.7 is possible, but at the limits of MPEG2 itself, and there will be a massive hit to quality.
There is another trick called MPEG statistical multiplexing, but that is a lesson for another day.
I'm an American, and I've gotten my grubby hands on a few BBC-HD rips (untouched not re-compressed). I can say that in both cases the video quality is better than any over the air channel in my market and MUCH better than the crap I get from Dish Network*. I only wish we had HD broadcasts at that quality. *Thats my subjective opinion.
What's all this hi-tech mumbojumbo? Can someone please use a car analogy to explain this to me?
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Now when we go to watch the Christmas special it will look like Cardboard sets, that wibble and wobble. The TARDIS will look utterly horrible and the Doctor will revert to a bloke from Liverpool with big eyes, big teeth, curly hair and a long scarf.
They also lowered the audio rate down to 16Kbps, so that rich orchestral music will sound like it came out of a cheap 1970's Moog.
Great, just when they updated the look of the show this will undo all of their work and it will look like the viewers were taken back to the 80's in an actual TARDIS.
Bravo BBC, Just Bravo......
Tsukasa: All I really want, is to be left alone...
The BBC claims 'We did extensive testing on the new encoders which showed that they could produce pictures at the same or even better quality than the old encoders ...' I got a good laugh off of this, but is it really possible to get better quality from a lower bitrate?"
i think they are referring to the combo of better encoders + the different bit rate. sure it's possible, if the older encoders were poor quality.
And I'll toss AT&T's UVerse. We have fiber to the house and the HD tv signal looks pretty bad on our 42" 1080p set. Sports are especially bad. Lots of blocking whenever there is any motion / pans.
Why not lower it to 12Mbps? Seems like a good compromise don't you think?
Going from 16 to 9.7 is like going from 100% to almost 50%, 100% to 75% @ 12Mbps is a lot easier to swallow.
Tsukasa: All I really want, is to be left alone...
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Comment removed based on user account deletion
Depending upon the configuration settings (frames per second, bit rate, I frame P frame structure etc.) it is most certainly possible to have a lower bit rate setting with better quality video than that of a higher bit rate setting. For example, if you drop the frame rate on a lower bitrate you often increase the quality of the video. So theoretically you can get easily the same quality at say 5 Mbps with a 15 fps as you can at 10 Mbps with 30 fps. I don't have specific numbers but subjectively (and empirically) it's quite possible.
There are definitely things that do make a difference here though, such as motion or high speed camera work. These types of video often suffer more noticeably than others so anyone watching sports, for example, will see the differences in quality more readily than someone watching a soap opera.
"Growing old is inevitable; growing up is optional."
They didn't die, they just moved on to bitching about the HD video in the old folks home....
Tsukasa: All I really want, is to be left alone...
Except one thing - ATSC digital television uses A/52b for audio (you probably know this as AC-3 or "Dolby Digital").
A/52b is a lossy audio format. It does not matter that you can get lossless compressed 48kHz audio that uses less bitrate than a raw PCM file (and it is likely that the compressed file is just PCM ran through a block-sorting compressor, e.g. gzip).
LAME at 160kbps gives better quality than L3A (Fraunhofer IIS's codec) at 256kbps, I'll give you that, as a lot of standards never quite specify details for the encoder, or allow a lot of flexibility in the bitstreams. But here, we are discussing ATSC digital television. You have to compare results against the same codec.
I am not aware if A/52b standardizes an encoder, but if not, then, like ISO/MPEG Layer-III Audio, it is quite possible (and quite often happens with ISO/MPEG Layer-III Audio, compare LAME v. hardware encoders) to have a decent software encoder produce better quality streams at lower bitrates than an inferior hardware encoder.
However, the only way that a lower bitrate can yield better quality is if the ATSC codecs are similiar to ISO/MPEG Layer-III Audio in that the standards only specify a decoder, leaving a wide variety of possible encoders. Without a standardized encoder, you generally end up with a less than optimal reference encoder (which was the case with ISO/MPEG Layer-III Audio) and a plethora of different hardware and software encoder implementations, each employing highly differing encoding schemes, providing highly varying quality yet bitstream compliant results.
The rest of Slashdot is rather technically clued-in, rather it's you that is technically clueless.
New codecs exist, like CIFF. h.264 codecs are a joke in comparison.
There are a new group of highly efficient video codecs that perform HD encoding at different bitrates, including loss less with extremely low (few ms) latencies. With some compression, it is truly amazing how much efficient a 4Mbps stream with HD content can hold. No floating point math is used and they scale out to use at least 8 threads, maybe more. Imagine encoding video with this codec on a 64-thread SPARC T5120 Server! Of course, you'll need both the encoder and the decoder, which I'm fairly certain the BBC doesn't have. http://www.freepatentsonline.com/y2006/0053004.html
This is serious stuff, not some vaporware. The code exists today.
I imagine its possible that a newer compression system could better choose what data was eliminated (while using the same compression format) based on a better understanding of how a human would perceive the outcome. Clearly, if this was the idea behind new compression settings, it did not work at the bit-rates the BBC tried. Not all compression systems (even ones that use the same format of compression) are created equal.
My intended reply was unpostable, because although Slashdot accepts the international symbols for pounds, yen, and dollars, it appears to want to filter out the unicode for euro, colón, Cuban pesos, kips, tugriks, nairas, won, baht, dong, and cents.
It's not like the international finance community isn't meeting you halfway. The Peruvian currency is the /.; what more do you want?
Please add support for more international currency symbols ASAP. Also, you're going to need to raise the moderation limit above "Score 5, Funny" for my post. I'd suggest going up to 11. It was going to be EPIC.
Although the quality matters, it also important that they can sustain the bandwidth. Everytime I have watched HD version of BBC's content I get buffering (I have 16Mb/s connection). This will be a good thing if it makes HD stuff watchable without constant buffering!
I think if the BBC wants to test if their new arrangement is degrading image quality, they should put up some randomized A/B pictures from both setups and ask users to pick. If they honestly believe the new setup is comparable then the results should be 50:50.
i did some a-b comparisons a while ago.. i was using handbrake.. CBR 700kbs.. between .mpeg and h264.. the h264 close-up pixel quality was superiour to the pixels of the mpeg clip.. whose file size was also larger.. h264 was so much better, in fact, that i vowed never to encode another film as mpeg again.. the cost however, is more processor usage.. mpeg can deliver a stutter-free picture on lower Mhz machines.. h264 gives better results & smaller size -- but requires more horsepower to interpret to the screen..
2cents from toronto island :D
jp
Earlier this year the BBC reduced BBC1 SD bitrate by about the same amount, by switching from 4.5Mbit fixed rate to variable rate. No-one noticed because most of time they just didn't need that bitrate. We actually have higher average quality now because the bitrate can climb well above 4.5 on demanding scenes. It was always annoying how much space BBC1 recordings needed on a PVR at the old rates and how it buggered up other channels in the mux.
That may be why they thought they could get away with dropping the HD rate, at least in management.
The BBC do not use MPEG-2 for HD transmission. BBC HD is only available via Satellite and Cable, not OTA, and is encoded using H264.
The reason it's not available OTA is because the DVB-T standard uses MPEG2, which is unsuitable for HD, at least at the bitrate that is available in OTA transmissions.
is it really possible to get better quality from a lower bitrate?
Yyyyeeessssss, maaaybe yyyooouuuu caaaan.
Yes, you can.
I thought if the motion compensation algo is better at 9mbits, than at 16, then it could look better, especially if there's a lot of action. Can't remember if the MPEG4/H.264 specs allow one to change it.
The again, it's BBC, all the shows are a bunch of folks sitting around a coffee table drinking tea with static images in the background, talking slowly.
Or at least that's how they explained British TV on Family Guy. You will see a difference with bitrate in that case.
We used to buy music on Records and CDs.
Now we listen to music on highly compressed mp3s. Most people have been listening to mp3s for so long they don't remember (or care) the difference of the higher quality of what a good record or CD used to sound like.
So give the people in the UK a few months and they won't remember what days with higher quality HDTV were like. Especially as we move towards streaming content. Comcast compresses, Netflix transmits audio in stereo. I can't wait for HDTV 1080bw (it's 1080p but in Black and White).
...' I got a good laugh off of this, but is it really possible to get better quality from a lower bitrate?"
That's not a problem. Apparently you don't understand coding. But then don't pretend you do, and laugh without understanding the issues.
Suppose I have an interesting high-res picture, but half of it is sky. Now if I code this in two ways. First I do a high quality jpeg. Very little bits go to the blue background, and lots can be allocated for the interesting parts. Also I save the original as a BMP (uncompressed). The BMP is MUCH larger than the jpeg. Now to reduce the number of bits in the BMP I scale it down by 2x on both sides. So now I might have a 6 megapixel JPEG, and a scaled down 1.5Mpixel BMP. The BMP comes to 4.5 Mbyte. But the 6Mpixel JPEG will look better and it has more details. Still it consumes less bytes (say only 1 or two Mbyte).
This is just an example where the lower bitrate can outperform a higher bitrate. Now I'm pretty sure that the old higher-bitrate encoding wasn't as stupid as being uncompressed as in my example. Still, it can very well be that the old codec was sufficiently outdated that it can be outperformed by a more modern codec at a lower bitrate.
However if you switch codecs people will be used to the old codec and its artefacts. So they will notice the change. Then you'll get complaints valid or not.
Anyway, even IF a modern codec can outperform an older one at a lower bitrate, it remains to be seen if this modern codec at 9.7 Mbps can outperform the older one at 16Mbps.
I'm fed up with hearing and reading how "digital TV delivers better quality images (and sound)". It does no such thing. It's obvious that the picture quality is poorer than a good analogue signal - some images break up altogether, like sunlight on rippling water. It may help cram more channels into less space, but that's not really an end-user benefit (it doesn't necessarily translate into more choice, here in Australia it just means more repeats).
Pictures at 11:07
We need a "+1 -- nice sig" moderation.
The lower bit rate creates severe and unattractive artifacts when Benny Hill chases scantily clad women at high speed.
But x264 doesn't support interlacing properly (or efficiently)? That's what I was told a while back. Haven't investigated it myself.
Most SDTV and HDTV content is interlaced, so not supporting proper interlacing makes a codec somewhat redundant...
Absolutely.
Given the verb: to be, to run, to go, to accept, etc. a 'split infinitive' is an instance in which a word or phrase (usually adverbial in nature) comes between the marker 'to' and the bare verb form ('accept' in this case).
Your usage was equivalent to: "to [something] accept."
You have split the infinitive ('to accept') with the adverb ('generally').
While this is more a style error than an all out grammatical error it is reasonably simple to avoid.
The split infinitive has been creeping into popular usage and acceptance since the early 19th century (c.e.).
My office has been taken over by iPod people.
If you find yourself nitpicking here, you need to question the usefulness of your life, and consider ending it.
All the new builds are GPON as well as any expansion in existing offices, Old Stuff is BPON, dont rememember the bandwith offhand. they also switched vendors , tellabs to that French company you might have heard of, Lucent(alcatel) :) and man the OLTs (co end) is incredibly compact 8U ~30k subs!
wanted: one clever sig,apply within
BTW Moca (cable) is 400mps cap vs 100 eth, Don't know what real world sustained bandwith is .
wanted: one clever sig,apply within