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Music Media

Bitrate Peeling with Ogg Vorbis 404

Posted by michael from the geek-cool dept.
Yort writes "Thought this might be interesting to some audiophile /.ers - there's been some discussion on the Ogg Vorbis lists, summarized in the most recent Ogg Traffic, about "bitrate peeling". In short, it's where you can simply "peel off" the high resolution data from the ends of an audio stream packet to come up with a smaller, lower quality stream. Brings up a number of geek-cool opportunities."
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Bitrate Peeling with Ogg Vorbis More

Bitrate Peeling with Ogg Vorbis

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  • Handy for porting your music to a portable player (Score:4, Insightful)

    by Anonymous Coward on Tuesday December 03, 2002 @07:28PM (#4805945)
    I don't know of any that play Vorbis files yet, but it would be very handy if I could take an OGG I had encoded at a high bitrate (for playback on my nice home stereo) and make it smaller for use on a walkman-type player for the gym or whatever.

    • And one more small improvement on that... (Score:4, Insightful)

      by Eric_Cartman_South_P ( 594330 ) on Tuesday December 03, 2002 @07:35PM (#4805994)
      ...having the Sync app automatically put the space saving lower bitrate file on the portable! Sweet. Of course, iPod'ers with 20 gig drives wouldn't lose sleep over it, but anyone with a Palm T or Sony NVxx would LOVE this.

    • Handy? Nah, Perfect! (Score:5, Insightful)

      by donutz ( 195717 ) on Tuesday December 03, 2002 @07:47PM (#4806112) Homepage Journal
      This is exactly the killer app that Ogg needs for acceptance: a program that syncs songs to your portable player at a lower (user adjustable) bitrate. Even better: You pick out X number of songs. Each time you add a song, it re-calculates what bitrate to shave them all to, to maximize the bitrate used, thereby using all the RAM on the player but getting all your songs in.

      I can't wait til this one hits.
      • Yes, but the average consumer doesn't give half a damn. Many of them don't know what a codec is, let alone differant bitrates. I'm sure very few people consider either when buying an mp3 player. From what i've observed, the two main forces are capacity and cost. As stated in another post, windows media player already supports this, yet I have yet to see someone use it. Many of the uninformed would rather buy a player with larger capactiy than deal with bitpeeling or reencoding.
    • it would be very handy if I could take an OGG I had encoded at a high bitrate (for playback on my nice home stereo) and make it smaller for use on a walkman-type player for the gym or whatever.

      Speaking of such, are there any Ogg-supporting portable players, or players in development?

      (Granted the Hardware Support page [xiph.org] at Xiph has some info, but I'm curious if there's anything else known)

  • audiophile /.er's? (Score:2, Insightful)

    by ehudokai ( 585897 )
    Wait a minute, I thought audiophiles always wanted to improve sound, not deteriorate it! Maybe the coders, like me, like this stuff, but my audiophile side is not interested
  • You could do the same thing with simple transcoding but this could be a lot more scalable.

    It would be even cooler if they could disperse the signal in time (i.e. across several packets) and just drop every n'th packet in order to create a lower bitrate stream without making it sound choppy.
    • Here's my understanding of the idea...

      First off, remember that Vorbis is a perceptual encoding scheme like MP3. What it does is breaks the sound at a given time into a number of components. The 'less important' components are filtered out, and the remaning ones are written to your file.

      For bitrate peeling to work, the sound data, when it's written, needs to be organized in such a way that it's trivial to look at the sound components and again figure out which ones can be thrown away to achieve the desired bitrate. ...and do it quickly w/o a large expenditure of processing power.

      Idealy, throwing away the least significant n frequency bands would give better results than just dropping every n'th packet.

  • good idea, but... (Score:4, Informative)

    by ameoba ( 173803 ) on Tuesday December 03, 2002 @07:34PM (#4805989)
    Bitrate peeling is a briliant idea, and would be a major win for Vorbis if they ever actually provide an implementation of it. It's something that the format supposedly supports, but right now it's still just a hypothetical application.

    Let me know when they've got something working THEN I'll be impressed
    • " Bitrate peeling is a briliant idea, and would be a major win for Vorbis if they ever actually provide an implementation of it. It's something that the format supposedly supports, but right now it's still just a hypothetical application."

      They (as in the ogg vorbis dev community) are saying it would be pretty cool for sampler tracks if you could save the 'peeled' bits. You could offer the low bitrate version for free. If people like it, they can pay extra for the peeled bits and then use some tool to re-integrate the free and peeled bits to get the full quality file.

      • Actually I don't get why this would be such a great thing. I mean why not download the whole track? The bandwidth you save because of the already downloaded bits from your low-quality sample is neglegtible.

        But for streaming and portable players, it's sure great.

        • "Actually I don't get why this would be such a great thing. I mean why not download the whole track? The bandwidth you save because of the already downloaded bits from your low-quality sample is neglegtible."

          Because whoever owns the server doesn't have to create and maintain multiple copies of the original file encoded at different bitrates. That would save them on hard drive space and file management too.

    • There was a bit of a discussion about this more than two years ago on the vorbis mailing list. As of that discussion, I got the impression that mpeg-4 had bitrate peeling.

      http://www.xiph.org/archives/vorbis/200005/0023. ht ml (no space between "ht" and "ml", of course: thank /. for that)

  • portables (Score:2, Interesting)

    by Anonymous Coward
    this brings to light the mp3/ogg hardware compatibility issue... ie: no portables/car stereos/dvds/home stereos supporting ogg, even though it's a superior format... i'm scared that it's going to suffer the betamax syndrome...

    personally, i'm converting over from 256kbps mp3 to 128kbps vbr ogg and i'm saving TONS of space and not really sacrificing any quality... does anyone know of a petition or something similar to get mainstream hardware manufacturers to include ogg support in their hardware?
    • are you actually trying to say that a 128 kbps Ogg sounds as good as a 256 kbps mp3 ? On my work PC I can't tell the bloody difference but at home a 128 kbps mp3 sounds poor and hollow. Granted the space back is nice but I'd rather keep my MP3's at 320 kbps and buy another drive to store them.
      • but what you just said has nothing to do with whether a 128kbps Ogg sounds like a 256kbps mp3.

        It's commonly observed that oggs of lower bitrate compare to mp3 at higher bitrates.

        • which is why I ASKED if the person honestly thought that OGG was twice as good ?? I really don't care on my end which format I use, I just want the closest to true sound. If an OGG track was actually as good as an MP3 of twice the bit rate it would be time to begin re-ripping things to Ogg Vorbis. As for space vs quality that is ALWAYS going to be an issue...

    • Re:portables (Score:2, Informative)

      by NickSD ( 595340 )
      >personally, i'm converting over from 256kbps mp3 to > 128kbps vbr ogg and i'm saving TONS of space and > not really sacrificing any quality... Although OGG Vorbis is superior to MP3, transcoding from MP3 to OGG will generally lead to a noticable loss in quality. Transcoding in general is bad, but transcoding down to a lower bitrate and between two transform codecs (as is the case) isn't really a great idea... but to each their own. With hard drives so cheap these days I'd just leave the MP3s as is. Especially considering most MP3s out on the P2P networks are encoded using outdated/flawed encoders such as Blade or Xing and are bad enough as is!
    • does anyone know of a petition or something similar to get mainstream hardware manufacturers to include ogg support in their hardware?

      It's not a petition, per se, but the Hardware Support page [xiph.org] at Xiph.org lists the contact info (including e-mail addresses) for companies considering Ogg support for their portable players.

      It couldn't hurt to write to them; I did.

  • similar to bit reduction decimation [angelfire.com] (look about halfway down the page for a quick explanation of decimation as an audio effect).

  • Audiophile? (Score:2, Interesting)

    by Quikah ( 14419 )
    Smaller and lower quality does not belong in the same sentence with the word audiophile. :)

    Cool idea though.

  • Audiophiles? (Score:4, Informative)

    by Pinball Wizard ( 161942 ) on Tuesday December 03, 2002 @07:37PM (#4806014) Homepage Journal
    So who out there is an audiophile and listens to compressed streams of music?

    Lately I've been finding all I can download off P2P programs like Direct Connect [neo-modus.com] and Furthurnet [furthurnet.com]. Its mostly live shows, and they are all in .shn format, which is a lossless compression format that restores to the original .wav file.

    These communities shun both compressed files like .mp3 and trading anything that has been released commercially. What you do get is great recordings of live music from bands like U2, DMB, Grateful Dead, etc., all ethically traded and in their full audio glory.

    The audiophiles I know pretty much don't listen to mp3, ever.

    • i'm glad you mentioned this. i wanted to bring something related to this up, but didn't want to be off topic. my problem is that i have a quite a large collection of mp3s, mostly stuff that i got back when i was in college. i never noticed that mp3s were not terribly good quality because my sterio system wasn't very good. mp3s always sounded like cds to me. however last week i went out and bought a damn good sterio system, and now i hear pops and cracks in some of my mp3s. not all of them, just a good fraction of them sound bad. the other ones are tolerable. does anyone know of a filter or something that i can run before the output to my sound card to get rid of the pops and cracks. i know that i'll never get back any quality that isn't there, but i'd like to at least not have the annoying cracks. i imagine that there's something out there that will work like /dev/dsp but instead do a little filtering. haven't been able to find it yet though.

    • Re:Audiophiles? (Score:5, Interesting)

      by Pieroxy ( 222434 ) on Tuesday December 03, 2002 @07:58PM (#4806198) Homepage
      Well, you should try then one simple test, that I did for myself and my friends. I just ripped a track of one of my favorites CD and encoded it with my favorite MP3 encoder (lame) to 160, 192, 256 kbps. I then burned a new CD-R with four tracks (original, 160, 192 and 256) in a random order. Since then, I'm looking for someone to be able to put those tracks in the right order.

      No one has been able to until then, and I'm not only talking (only) about average people. I have some friends which (unlike me) have a decent equipment.

      Usually these guys were able to clearly distinguish 160kbps from the set. With 2-3 pass they detected the 192kbps track and they couldn't tell the difference between the 256kbps and the original.

      Maybe I could send you guys some samples...

      Just keep in mind also that MP3 is the same type of compression than DTS & AC3 (Dolby Digital) and I've never heard someone complain about those (especially DTS). If you're unhappy with quality, just increase bitrate. And if those guys in the MPEG consortium felt that 320kbps should be the maximum, It should mean something.

      Lossless compressors have such a poor ratio!

      • Re:Audiophiles? (Score:2, Interesting)

        by mindstrm ( 20013 )
        what's decent equipment? The audiophiles out there will want to know. Also, what was the test material?

        You can argue that 256 is the same.. and for your purposes, it probalby is. For most common equipment, it surely is.

        Someone with a really well educated ear and really good equipment can probably hear the difference though. Because there IS a difference.

        Another thing... with high bitrate mp3.. when comparing between an original and the compressed version in a blind test, someone will be able to tell you they are different, but not which one is the original... becasue both sound good.

        • Re:Audiophiles? (Score:3, Insightful)

          by Bronster ( 13157 )
          Another thing... with high bitrate mp3.. when comparing between an original and the compressed version in a blind test, someone will be able to tell you they are different, but not which one is the original... becasue both sound good.

          Well duh, then what's the problem? If they both sound good then you'll enjoy either one, so listen to the one that uses less bandwidth.

          *sigh*

          • Re:Audiophiles? (Score:2, Insightful)

            by mindstrm ( 20013 )
            Of course. It all depends on what *YOU* are after, and how you enjoy music.

            Many "Audiophiles" enjoy listening to how accurately they percieve their setup to be reproducing the original sounds... that's why they don't like lossy compression. It's not because it doesn't sound good.. it's because they are chasing accuracy. This accuracy becomes as important to them as whether or not they like the tune in the first place.

      • Re:Audiophiles? (Score:3, Informative)

        by NickSD ( 595340 )
        First of all, for the best quality out of the LAME MP3 encoder, you shouldn't be using those CBR modes (160, 192, etc). Use either --alt-preset standard or --alt-preset extreme for best quality. Those presets are better in many ways than the CBR modes you mentioned.

        Secondly, I understand that it is hard (and sometimes impossible) to hear the differences between a properly-encoded MP3 and the original, but that does not mean it will be true for all cases. Music varies greatly, and while you may not be able to hear a difference on certain songs, there may be others where it is quite apparent. I don't think anyone can debate (anymore) that a properly-encoded MP3 using --alt-preset standard with LAME is easy to pick out. Most of the time, to most people, it will be transparent. However, arguing that people should use MP3 over lossless is a whole different ballgame.

        One nice thing about lossless is that you always have the choice of converting it back to the original WAV and using that as source data for further processing. Once you've converted something to MP3 (or any lossy format) you can't go back. There are applications for lossy and applications for lossless, but I think comparing the filesizes and claiming MP3 is the way to go isn't really appropriate. Just IMHO, of course. I am speaking from the point of view that your intent is to archive your audio or something similar.

        • Re:Audiophiles? (Score:2, Insightful)

          by Pieroxy ( 222434 )
          I totally agree with you. But for different reasons (including some hardware MP3 decoder bugs) I did choose CBR 256kbps to backup my CDs.

          I'm using MP3 to backup my CDs. I've broken a couple of CDs recently (partly because of my 1 year old son ;-) and I just want a backup. 256kbps quality cannot be picked up from the original (at least by anyone I know and by listening) on $450 headphones. I think that'll do it.

          To try and answer everybody, you actually made a point I failed to address. MP3 should be used for LISTENING. The whole point of this compression is to remove frequencies that the global level of music is masking. Therefore, if you take an MP3 and apply a filter out of it (any kind), you will loose A LOT OF QUALITY, because the point of any filter is to modify the original and so some frequencies that were masked could have become audible.

          Besides that, the main problem with MP3 is not a masking of frequencies but artifacts (I said the MAIN problem, of course frequency loss counts). The psy model used in an mp3 encoder will allow strong artifacts that could (and will) show up if you apply basic filters.

      • Re:Audiophiles? (Score:3, Informative)

        by tswinzig ( 210999 )
        Just keep in mind also that MP3 is the same type of compression than DTS & AC3 (Dolby Digital) and I've never heard someone complain about those (especially DTS).

        Yes I've heard Dolby Digital compression is similar to MP3 compression. However, DTS uses very little compression, which is why it sounds better and takes up more space on your DVD disc. Check out the DTS FAQ [dtsonline.com].

    • Re:Audiophiles? (Score:3, Informative)

      by pthisis ( 27352 )
      Shorten (.shn) is not a free program (libre--it is gratis). It also doesn't compress as well as some of the other lossless codecs and as far as I know there aren't any hardware devices that support it.

      I use FLAC to compress my music, which is free and lossless. It outperforms shorten on average (smaller compressed files), and is also supported by some hardware playback devices (Rio, Phatbox, some Kenwood stuff) unlike Shorten.

      I play back through a Hoontech card with digital output and use an offboard MSB Link DAC III (the computer is acoustically isolated from the listening room) which feeds into a Creek 5350 integrated amp driving Vandersteen 2ce Signature loudspeakers.

      I also use lossy compression for my car mp3 player--the stereo there isn't audiophile quality anyway.

      Sumner

      • Re:Audiophiles? (Score:3, Informative)

        by NineNine ( 235196 )
        play back through a Hoontech card with digital output and use an offboard MSB Link DAC III (the computer is acoustically isolated from the listening room) which feeds into a Creek 5350 integrated amp driving Vandersteen 2ce Signature loudspeakers.

        And we should care about this, why?
        • That's audio geekspeak, not the computer geekspeak we're used to. Imagine if he had been describing a gaming system and said "I've got an 4 way xeon each w/ 4MB of full speed cache with a kernel patched to bind them to each to one of 4 of the Wildcat video cards genlocked together and each in turn connected to a 5000 lux projector which back display on my 8' cubed CAVE."

          I'm not an audiophile myself but find their utterances interesting.
      • ...but how many vacuum tubes do you have in your system?

        The true measure of an audiophile.
    • So who out there is an audiophile and listens to compressed streams of music?

      Audiophile = someone who loves audio. The guys who sell $14,000 record players have extended the meaning of audiophile to "someone who loves audio and is willing to spend five or six figures on the fanciest looking equipment."

      So by the dictionary definition, yes, there are many thousands of "audiophiles" who enjoy MP3. Get over it, for chrissake.

      Its mostly live shows, and they are all in .shn format, which is a lossless compression format that restores to the original .wav file. These communities shun both compressed files like .mp3

      Having said that, there is actually a good reason why lossy codecs are especially bad at encoding live shows. Lossy codecs do their magic by removing info that is "masked". Eg if two sounds are close in frequency but one is significantly louder, the human ear/brain will only hear the louder one. MP3 does best with sounds that a) can be broken down into a smallish number of frequency components and b) contains a lot of elements that the human ear can't perceive.

      The problem with live music is that is is exactly the opposite of a studio recording in those respects. It cotains a lot of "noise" (eg applause), which has a broad spectrum, plus a lot of quiet stuff like background murmurs, which we *can* hear. It's just much more complex.

      You just need to use a higher bitrate for live than you do for studio recordings, and everything will be fine. Unless you've done a double-blind A/B test and can tell the difference between a good CD and a good MP3, I'm really not interested in your opinion on what "audipohiles" should be listening to.
    • I remember having a long debate with a so-called audiophile who had much more money than sense.

      He was bragging about his expensive (and therefore wonderful) setup, when he mentioned having "super-high quality" digital cables, which cost him $2,000. I asked him how much "low quality" digital cables cost, the answer? About $15!

      I asked him what the difference between the two was, he claimed that the high-quality digital cables gave the music more "body"!

      It may have been cruel of me, but I just couldn't help but explain what digital actually meant.

      The moral of the story? That much of the audiophile community are simply the blind leading the blind, pseudo-techie alchemists, who assume that expensive means better.

      • oh come now, of course it sounds better with the higher quality cable, I mean, the bits are more easily recognized, they have less distortion and the processor can determine weather it is a bit or not more accuratly and in precise time...

        me, I bought the $15 cable.
        (Somebody somewhere is going to have to spend a week with me and explain why you have to worry about jitter in any piece of equipment *EXCEPT* the last one.

        And even then I have my doubts, but atleast it is possible to measure jitter.

    • Re:Audiophiles? (Score:5, Informative)

      by Monkelectric ( 546685 ) <slashdot.monkelectric@com> on Tuesday December 03, 2002 @08:56PM (#4806631)
      I am a certified audiophile... High bit rate mp3 are very difficult to tell from the original... however most mp3s are made by amateurs with bad encoders that are *crap*.

      Before encoding my cd collection I spent a month playing with different encoders and settings to find what might satisfy my ears. I eventually settled on lame with the "new vbr method" and the highest quality settings and I've been very happy with the results. If something better comes along, I'll get my CDs out from under my bed and re-encode :) The only time I've been able to tell one of my mp3s from the CD is on albums I am intimately familiar with, i.e. the Steely Dan Box set. I have easily heard it 500 times, and every once in awhile you notice the timbre of a cymbal is just a little bit different then you remembered it.

      However, something no one ever thinks about is your mp3 *player* and sound card. An internal sound card is worthless for listening to music (I use a M-Audio Delta1010 which is part of my studio setup). Also the mp3 player makes a *huge* difference. It will probably come as no surprise that Winamp is shit. I like CoolPlayer [sourceforge.net] which is based on libmad -- a 24 bit integer only mp3 decoder. The extra bits are important because they reduce quantization errors during decoding, there is a noticeable difference in clarity between coolplayer and winamp. Also, standalone MP3 players tend to have better mp3 decoding because they (usually) use a DSP to decode the and DSP programmers are well aware of accuracy issues.

      My point is, mp3 is tolerable for casual listening even to an audiophile *IF* it's done correctly. The problem of course is that the computer is about the *worst* place to be listening to music because its at such a disadvantage (poor quality signals, noisy electronics, bad DACs, shitty speakers).

      However, your need for a higher quality signal is directly proportional to the cost of your stereo. If you have a small portable stereo, the radio is about the best quality you can reproduce anyways. The quality of mp3's is superior to what the average computer can reproduce. But If you have a 30,000$ stereo as some obsessive audiophiles do, its pretty silly to listen to mp3s on it (but you're gobbling up dvd-audio discs as fast as they are made anyways).

      • Re:Audiophiles? (Score:3, Interesting)

        by Sycraft-fu ( 314770 )
        Interestingly enough I find that MP3 can even give superior sound to CD if encoded and decoded properly. MP3s don't have a set word size like PCM audio does, they just take the data they are given. Good encoders, like LAME, are perfectly capable of taking 24-bit files as input. At high bitrates (256-320k) I find that the compressed MP3 sounds superior to a 16-bit PCM file when taken from a 24-bit source, despite being smaller.

        By the way, you might want to check out the MAD Winamp plugin at http://www.mars.org/home/rob/proj/mpeg/mad-plugin/ . It offers good 24-bit decoding in Winamp, which I happen to really like as a player.
    • The audiophiles I know pretty much don't listen to mp3, ever.

      I can understand ones love for quality music reproduction. Some people take it to the extreme but to each his own. I define an audiophile as someone that lost entertainment value of the music and became overly concerned or even obsessive with nothing but the quality. An example is your statement above. Basically an audiophile is not happy with anything but the perfect listening environment using his own home made speaker interconnects, directional wires, and triple filtered power supplies. How can you enjoy music the other 98% of your day, like when on the subway, in your car, at a night club etc.. I truely enjoy a good relaxing listening environment (at least on a moderate budget) but I also can hear any track from Dark Side of the Moon on AM radio and still get enjoyment from it.

  • Stripping data, eh? (Score:5, Funny)

    by radiumhahn ( 631215 ) on Tuesday December 03, 2002 @07:39PM (#4806033)
    I always kind of felt the first and third bit of every byte were kind of unnecessary. I'm not to fond of the F6 key either!

  • Alternative use.. (Score:5, Interesting)

    by irc.goatse.cx troll ( 593289 ) on Tuesday December 03, 2002 @07:41PM (#4806043) Journal
    "Beni Cherniavsky mentioned a very intriguing counterpart to bitrate peeling. If you have a peeler that saves the bits it chopped off, you could reconstitute the higher quality files by adding the missing bits to the lower quality file. This idea could lead to a music download service where you can download a low quality preview version of a song, and if you are interested, download the missing bits to make it a high quality version."

    Or, Slightly modified, You could share all your high quality oggs on a P2P network, and have your client peel it down to 'future-legal-to-share' low quality files.

    • Re:Alternative use.. (Score:2, Interesting)

      by blinkie ( 27148 )
      and since it's apparently possible to cumulatively download those missing bits, you could be downloading quality instead of time. sounds like an interesting (I'm not saying better--yet) alternative to those gazillions of cropped media files hanging around..

    • Re:Alternative use.. (Score:5, Insightful)

      by david.given ( 6740 ) <dg@cowlark.com> on Tuesday December 03, 2002 @09:18PM (#4806743) Homepage Journal
      "Beni Cherniavsky mentioned a very intriguing counterpart to bitrate peeling. If you have a peeler that saves the bits it chopped off, you could reconstitute the higher quality files by adding the missing bits to the lower quality file. This idea could lead to a music download service where you can download a low quality preview version of a song, and if you are interested, download the missing bits to make it a high quality version."

      Or, even more interesting: peel a Vorbis file all the way down to the minimum quality. Concatenate the bits together in order. Now you have a file that you can play back, in its entirety, when it's only 10% downloaded. All you have to do is wait for the minimum quality version to download; from then on, the entire file is playable. It's just that the longer you wait, the more peels get added, the higher the quality... holographic audio downloading.

  • What seems cool about this is that the bits could be peeled dynamically so that there are no skips when listening to a stream online. This would require some kind of overhead from client to server to transmit dynamically changing bandwidth requirements. Now, for one step cooler. If the streaming server was keeping accurate track of the peeled bits, it could transmit them transparently to the end user intelligently either during or after the current stream so that the end user could listen in pristine quality the second time around! ...I can already see services charging the end user a premium for this type of benefit.

  • Is this really such a useful idea? (Score:3, Insightful)

    by Tsar ( 536185 ) on Tuesday December 03, 2002 @07:46PM (#4806094) Homepage Journal
    This feature is unique to Ogg Vorbis...Bitrate peeling is not actually implemented yet.

    Sounds more like it would be unique to OV, if they implemented it.

    The point is, nobody does it now. Perhaps this is because there's really no need for it. Consider the list of "very sexy applications:"
    • In a streaming situation, the server would store only one high quality stream, and dynamically peel it down to the client's bandwidth. Not useful. If you instead stored a hundred separate files, each optimized for its bitrate, with each being half the bitrate of the previous one, you'd still have a set of files less than twice the size of the largest file. Plus, you'd have no bit-peeling overhead. If you're streaming 100GB audio files, maybe there's a benefit, but if you're doing that, you can probably afford a second 100GB file for all the smaller files.
    • You could store high quality Ogg Vorbis files on your PC for your Audiophile home theater setup, and peel them down to "good enough for lousy headphones on a noisy train" portable files. You can do that now, without this high-tech. Such low-quality files could be easily made from the original OV high-quality files, without much extra artifacting due to the re-encoding. And again, how low a quality are you willing to accept, if you're going this far anyway? Wouldn't you just buy a higher-cap memory card?
    • Download a low quality preview version of a song, and if you are interested, download the missing bits to make it a high quality version. Another non-benefit. Suppose the full file is 10 meg, and you download a 1 meg sample. Are you really going to opt to download the 9 meg "patch" file, rather than the 10 meg complete version?
    A clever idea, and it sounds cool on the outset, but it seems to me that this is a solution seeking a problem.

    • Remember back when you could choose to download large files in one chunk or in floppy-sized portions? Often even if you didn't intend to put them on a floppy you'd get the split version if you didn't trust your network connection -- or if you didn't have time to download the whole thing. Today we have rsync -- isn't it a Good Thing (TM)?

      For audio being able to download partial files or skrink a file isn't a big deal because the files rarely get huge (if it's long, it's probably voice and therefore can be compressed to hell), but for video this is a big deal. I won't go into the applications, just read a bunch of the other posts and 1,$s/audio/video/g* but notice how much more sense they make when you're talking about things that barely fit onto a single DVD now. For example: imagine watching streaming video that, once it's downloaded at a minimum acceptable quality, starts to improve while you're still in the middle of watching it (or even while it's sitting on your HD and your computer doesn't have anything better to do).

      Asides from any practical benefits, bitrate peeling introduces the concept of a file storing multiple, modular representations -- which is certainly as profound as moving metadata inside of files.

      * That's replace all copies of "audio" with "video" for the vi-impared.

    • The advantage is that you can store just one high-quality file and then generate any intermediate bitrate without reencoding which causes a loss of quality. Your disregard for file sizes is silly and irrelevant since it will only let you use bitrates you plan for at the beginning instead of simply storing the highest possible quality once, or in terms of normal use of disk space, the highest quality you think you're likely to need.

      You will get plenty of reartifacting during reencoding since you are going to such a low quality. It is MORE important to have as much information available as possible when encoding to a low bitrate, not less.

      Your question "Wouldn't you just buy a higher-cap memory card?" is incredibly arrogant and dismisses inexpensive but nonexpandable devices of the future which will support ogg and cost nearly nothing. Before long we'll be getting shit like earrings with a bluetooth interface that play oggs for free in our cereal boxes, and they won't have upgradable memory. That's not the real issue though, which is that right now memory cards cost money and some people store up their money and buy a player and can't afford more than the 32mb the base model comes with. (That's not me, I'd rather use CDs at that point, but you catch my drift.)

    • What about LIVE streaming? Should the audio source encode 10 different versions at once, and send double the bandwidth to the repeaters? Bitrate peeling is a great benefit for live streaming, it will reduce the upload to a single stream and take processing power requirements away from the encoder.

    • A spurious example (Score:3, Interesting)

      by benwaggoner ( 513209 )
      Okay, if each one is double the one before, that means you'll have a 2^100 ratio between lowest and highest data rate. Thus, if your lowest is 1 Kbps, the highest would be... Not going to happen that way.

      Also, you assume the sweet spots are 2x the one before. In fact, jumps of more like 1.25 are likely to be optimal (albeit with a lot fewer jumps!).
    • In a streaming situation, the server would store only one high quality stream, and dynamically peel it down to the client's bandwidth. Not useful. If you instead stored a hundred separate files, each optimized for its bitrate, with each being half the bitrate of the previous one, you'd still have a set of files less than twice the size of the largest file. Plus, you'd have no bit-peeling overhead. If you're streaming 100GB audio files, maybe there's a benefit, but if you're doing that, you can probably afford a second 100GB file for all the smaller files.

      It would be great for multicast-type situations (including, but not limited to IP multicast.) You could send one high-quality signal out from a central point and then shave off bits to fit the stream down to the quality needed by the end-user.

      For instance, users on a 56k modem could listen to the same multicast stream as a broadband user (ie, no need to send out multiple, separate versions from the source)-- this assumes the presence of routers (or conversion boxes) capable of doing the peeling as needed.

      All in all, very useful.

    • Looking at your example of storing the variable bit rates as seperate files as an example, let's do some theoretical math:

      Original High Quality file: 10mb
      3/4 Quality file: 7.5mb
      Half quality file: 5mb
      Quarter quality file: 2.5mb
      Total for all variations without peeling: 25mb

      Or, store the High Quality 10mb original only and dynamically peel. Savings, 15mb (1.5 times more files)
      No need te reencode a new file for each device (and some of us have many!)

      Just FYI

    • Yes, it is a very good idea. (Score:5, Insightful)

      by HopeOS ( 74340 ) on Tuesday December 03, 2002 @09:33PM (#4806811)
      There are a number of problems with the parent post.

      1. Keeping hundreds, or even ten separate files as described, each half the size of the previous, is not plausible. I'd assume the author was a troll, but since no one else has mentioned it, perhaps the obvious fallacy with that idea is slipping past even the sharper readers. A 10MB file can be split in half at most 23 times before it is only 1 byte long, far fewer before the quality level is unacceptable. Secondly, the idea described in the article, provides for dynamic bitrates, not simply half the original bitrate. To provide even similar functionality, one would need files in ranges from 1MB to 10MB in relatively small increments, totaling well in excess the "twice the size of the largest file" as suggested. Even so, this would be deficient in that the bandwidth could not be throttled mid-stream.

      2. Second, decoding and re-encoding the same file with a different bit rate will almost certainly result in poorer quality than the technique described. The safer, more straightforward solution, is to perform reduction operations on the transformed data, rather than the decompressed waveform. Otherwise, amplified artifacts from the original compression will be present in the new file.

      3. Third, the strength of the poster's argument lies entirely in the choice of ratios. Downloading a 5MB file rather than a 10MB file leaves only 5MB remaining. To paraphrase, are you really going to opt to download the 10MB complete version when your software can download the remaining 5MB in half the time?

      There are a number of problems which bitrate peeling address, not the least of which are 1) reduction of storage space as described previously, 2) dynamic bandwidth regulation of audio streams for streaming radio, future cellular phones, VOIP, and network appliances running on congested networks, 3) file size reduction without transcoding, 4) user-specified bandwidth on demand, 5) automatic preview generation from source without any extra administrative overhead.

      I'll even add my own... the ability to download a very high quality file and start listening to it immediately at lower quality without interruption. By the time the file has played through, the download may be only 50% complete. If I decide not to continue with the download, I have wasted no more time than that necessary to listen to the file. If I want the file, I have only 50% remaining.

      In some ways, this is similar to the rationale behind interleaved images, except that it is unlikely that you will need to listen to the same file repeatedly at progressively higher bitrates. Nothing prevents this of course.

      -Hope
    • Sounds more like it would be unique to OV, if they implemented it.
      For audio, maybe. SPIHT [rpi.edu] implemented a scheme for image compression where you could just whack the bits off the end of the compressed data for an image and get a lower-resolution version (choose an arbitrary compression rate and it's simple to generate). And an Israeli company called VDO did something similar for video, where lowering the resolution was a simple matter of whacking off the last bits for each frame.

      This appears to be a fairly natural thing for compression based on wavelet transforms, which were used by both SPIHT and VDO.

    • Not useful. If you instead stored a hundred separate files, each optimized for its bitrate, with each being half the bitrate of the previous one, you'd still have a set of files less than twice the size of the largest file. Plus, you'd have no bit-peeling overhead.

      No, you're right, the overhead would instead be up-front, having to encode at multiple bitrates, and more overhead in storage costs. It's a tradeoff.

      Suppose the full file is 10 meg, and you download a 1 meg sample. Are you really going to opt to download the 9 meg "patch" file, rather than the 10 meg complete version?

      Why are you assuming the worst-case scenario? What if I downloaded a 5MB version, and now I only need the other 5MB? Multiple that times 10 tracks, and that's only 50 more MB I need to download, instead of another 100MB. Now assume the client you're using to handle these purchases is smart and does this all in the background. Yes, it's a great benefit!

  • You're Right (Score:2, Interesting)

    by stsai ( 463884 )
    If you read many of the audiophile magazines such as Stereophile, etc., you'll see reviews of equipment such as external DACs for CD players as well as many high-end CD players. Among those there is the legendary Linn Sondek, a CD player which retails for around 21k.

    Why would you need a 21k CD player, you ask? If a CD player is playing back an exact digital file, than shouldn't all CD player's sound the same? The answer is simple: let your ears be the judge.

    I was initially skeptical when I was first shopping for stereo equipment, but there is a world of difference between a consumer CD player obtained at the chains like Best Buy, Fry's, etc. and an audiophile CD player. The difference is primarily in the level of clarity or resolution that you can hear from a quality CD player. The difference is subtle yet dramatic, you can hear instruments and detail that you simply could not make out before.

    To make a long story short, the quality of mp3s is typically even below that of a CD played on a cheap consumer CD player. No "audiophile" will listen to them as a primary audio source. That said, I have an mp3 player that I use when running and I have mp3's on my computer. Everything has its place, but the place of mp3's or ogg is not in audiophile stereo systems but in the world of music sharing where file size is a critical issue.

    • Re:You're Right (Score:2, Interesting)

      by mindstrm ( 20013 )
      There is so much fluff in the audiophile world it's hard to tell what really makes a difference and what doesn't. Really, like computer hobbyists, it's really about what makes you happy.

      Many non-audiphiles like to listen to music because they like the tunes and lyrics, not because they want to super-analyze every insturment. In this respect, mp3 & ogg & whatnot are fantastic. If they suck, why are they so popular?

      So.. you tried this CD player in the same audio setup you were used to using, to compare it side by side with another player you were used to with no other factors that change?

      yes.. there are differences in CD players... mostly due to oversampling & better filters, and good quality output components. That, and good power supply circuits.

      The difference between a cheap cd player and a $1000 cd player will be noticeable; the difference between a $1000 player and a Linn Sondek is more debatable.

  • Audiophiles? (Score:5, Funny)

    by usr122122121 ( 563560 ) <usr122122121@PAR ... h.com minus city> on Tuesday December 03, 2002 @07:57PM (#4806186) Homepage
    Musi withou hig frequenc is lik wods mising leters.

  • This reminds me... (Score:5, Funny)

    by dubious9 ( 580994 ) on Tuesday December 03, 2002 @08:04PM (#4806258) Journal
    of a Slashdotter comment that twisted an old expression...

    "Those who sacrafice sound quality for hard disk space deserve neither."

    Cool idea to throw around though.

  • Peeling! (Score:5, Interesting)

    by Emmettfish ( 573105 ) on Tuesday December 03, 2002 @08:05PM (#4806262) Homepage
    Okay, I'm biased in this discussion: I am the CEO of Xiph.org [xiph.org] and I'm also a musician [diff-eng.net].

    One thing that hasn't been discussed here is that a lot of people feel that Vorbis is transparent at something like quality setting 4. Other people think it's transparent at quality setting 3. Others think it's great at 1. I release my stuff at 4, but bitrate peeling will let people peel those down to what sounds good to them. Maybe they want to monkey with it, and maybe they don't, but the option to do this without re-encoding is sexy.

    It's not just a 'chop it down for modem folks' thing, it's also a letting people choose for themselves situation that I think is more important.

    Features are cool, but features that give people options apart from 'use it or not' are even cooler.

    That's it for me. Please donate [vorbis.com] to Xiph.org, and then go listen [diff-eng.net] to some tunes. Enjoy!

    • Re:Peeling! (Score:5, Informative)

      by Jucius Maximus ( 229128 ) on Tuesday December 03, 2002 @08:26PM (#4806396) Journal
      "Please donate [vorbis.com] to Xiph.org, and then go listen [diff-eng.net] to some tunes. Enjoy!"

      I really would like to donate, but not through PayPal [paypalwarning.com]. Could you please offer some other method of payment like the Amazon Honour System [amazon.com] or Element5 [element5.com]?

    • There is a such thing as too many options. Would you like to try and explain this to my mom who can't use our HDTV remote control?

      I'm not all that familiar with Ogg so I'll give you the benefit of the doubt here that this is cool. However Ogg has enough working against it in the form of MP3 that adding complexity to it is going hinder it's acceptance, not increase it.
    • Maybe they should "go listen" and on that page you can ask them to "please donate". The reverse seems a bit strange.

  • Cool, but not unique (Score:5, Interesting)

    by benwaggoner ( 513209 ) <ben.waggonerNO@SPAMmicrosoft.com> on Tuesday December 03, 2002 @08:20PM (#4806364) Homepage
    Scalable techniques like this are very cool, but hardly novel.

    MPEG-4's scalable profiles provide a similar effect (albeit in the other direction, with enhancement layers). Some of the higher end audio codecs (beyond CELP and AAC), like ER BSAC (Error Resistant Bit Sliced Arithmetic Coding) do exactly this. The idea in this case is that the server will in real-time only provide as many bits as the connection can currently provide. Very nice for wireless.

    QDesign's QDX format does almost exactly what is described for Ogg, with arbitrary bitrate peeling down to the 1 Kbps level. The idea is that you could copy as much data as you want to your mobile player, and it'd dynamically thin to the data rate that would fill up your device.

    And still image codecs like JPEG have used progressive modes for years, where additional data adds more detail to the image.

  • Progressive Ogg? (Score:3, Interesting)

    by Luke-Jr ( 574047 ) on Tuesday December 03, 2002 @08:36PM (#4806470)
    Could it possibly be used to progressively download an Ogg file and begin listening to it before it's 100% done? For example, have the 32kbit quality at the start of the file, then next have the next 32kbit (starting at the end of the file), then the next 64kbit, etc...

  • All these anti-peeling posters are retarded! (Score:5, Interesting)

    by Ayanami Rei ( 621112 ) <<rayanami> <at> <gmail.com>> on Tuesday December 03, 2002 @08:55PM (#4806625) Journal
    There aren't ANY free lossy codecs that can do bit-peeling right now. Some non-free codecs allow you to overlay data (like progressive JPEG), which is NOT the same thing. That's just like transmitting deltas at higher compression rates, which could be done with a simple side-band for any existing method, MP3 even.
    The only option is transcoding, which compounds compression errors (decode, reencode). I often wished the MPEG group would have been more intelligent in the design of their bit-allocater so that you could "thin out" the quantization of the power bands by looking at the "right parts" of the MP3 frame. Alas, this is not possible.

    But the Vorbis designers have made this possible, thus making it possible to have high-quality and low-quality versions derived from the same source file without additional processing. I imagine you have certain restricted choices, due to how quantization information is bundled up/packeted. But it isn't just sexy, it would be stupid to NOT DO IT. It takes just a little forethought on how to lay out the information in a hierarchial fashion. What makes anyone think that this is any harder then decoding/reencoding. I guarantee it has a time complexity on the order of a straight copy.

    Hell, formats like SHN and FLAC can do it, just substitute short codes for long codes at a certain rate; it'll add a bit of wide-band energy on decode, raising the noise floor in proportion to the space savings you gain.

    So anyway, "poop on you" to all these wanna-be audiophiles/slashdot-know-it-alls who don't no a good thing when they see it.

    Don't like it, keep sucking on that Layer III.

  • DTS has similar system (Score:4, Informative)

    by nedron ( 5294 ) on Tuesday December 03, 2002 @10:19PM (#4807071) Homepage
    The home theatre version of DTS [dtsonline.com] uses a similar mechanism, allowing DTS to continue to add discreet channels and additional features while remaining compatible with older DTS decoders. Basically, the decoder ignores any information in the stream header that it doesn't understand.

    That's how DTS was able to add a discrete surround channel (DTS ES) without causing problems with older receivers. Dolby can't change their header without breaking backward compatibility, which is why their extra surround channel (DD EX) is matrix encoded.

  • iPod seems to do this anyway (Score:3, Interesting)

    by Richard_J_N ( 631241 ) on Tuesday December 03, 2002 @10:22PM (#4807091)
    I think that the iPod does a very bad attempt at this. MP3s, encoded at 320k play back really badly on the iPod, far worse than 128/192k ones. I suspect that the iPod hardware hasn't enough horsepower - and it is discarding bits that it cannot decode fast enough. The MP3s sound fine on the pc, or decoded to wav and then played back on the iPod. But played back (as MP3) on the iPod, the result is dismal - there's a 5Hz "wobbling", rather like a steel band, and lots of distortion. (Apple won't help, but I have replicated this problem on multiple setups both Linux and OSX - it would be interesting to see if any /.ers have seen the same thing. You need a good recording of a classical CD with very large dynamic range eg Mahler 8, part II to demonstrate it - listen to the quiet bits.) [I have some demo files, but can't link them - I'll get slashdotted off the net !]
  • I've been unable to get a decent answer here.

    Why can't we peel away detail from an MP3? It's pretty clear we can't, but why?

    The *massively* simplified description of how MP3 works is as follows: Grab a chunk of sound, call it a frame. Split the frame into 576 frequency bands, figure out which ones the psychoacoustic system cares about for a given period of time, and reduce detail against whatever's left. This process, quantization, is roughly equivalent to rounding 1.1241 into 1.1. Move ahead half a frame, and do it again.

    There's a bunch of other funkiness -- looking at previous frames to figure out what's important in this one, losslessly encoding frame data whenever possible, and of course, the actual algorithm used to allow frequency quantization (the Discrete Cosine Transform) -- but at it's core, MP3's just "chop, split, pick, and trash".

    Now, at the end of the day, an encoded MP3 contains unquantized material -- larger MP3's trash less. Why can't I go into the larger MP3, throw out more data, fix up the headers, and shrink the size of the file?

    Yours Truly,

    Dan Kaminsky
    DoxPara Research
    http://www.doxpara.com
  • Okay, this has been effectively added to MP3 Pro, and was what they were calling their revolutionary next step. Basically, they took the stream and separated it into a high range and an low range, then compressed these streams separetly so that the delta values were much smaller. If you played the mp3 pro file back in a regular mp3 decoder, you would only get half of the stream. I suggest this not be added to OGG as it tremendously increases the amount of processing power required to decode. I know that a lot of people want OGG in portables, but this is just too much of a drain on the mobile devices.

  • adaptive peeling (Score:3, Interesting)

    by aminorex ( 141494 ) on Wednesday December 04, 2002 @02:41AM (#4808308) Homepage Journal
    For streaming without "buffering...75%" interruptions,
    adjust the peel factor on the fly.

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