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Streaming FLAC over the Internet, Split from "The Future of FLAC"
andrewfg
post Nov 22 2012, 12:06
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IMHO flac has one technical weakness that will prevent it taking off as THE standard -- namely it only has Variable Bit Rate compression algorithms. Which means that one cannot predict in advance the length of ouput file that will be generated for any input stream.

This is a problem when you want to transcode another format of audio file to flac and stream it over Http. The Http protocol requires sending a Content Length (number of bytes) header at the start of the streaming process. With flac you cannot know the number of bytes until after the full file has been transcoded. So this means that Http must either wait until the full transcoding has been completed, or alternatively if it wants to start streaming the data immediately, then it must provide some guessed value in its Content Length header (and this is not conformant to the Http specifications, and may cause problems in some music players...)

By contrast, if you are (say) transcoding to mp3 and streaming that via Http, then the transcoder can select a Constant Bit Rate compression algorithm. And in such a case, the Http Content Length is easily calculated in advance as being the input audio file's duration (in seconds) multiplied by the CBR rate (in bytes per second).

So if the flac standard were extended to allow both the existing Variable Bit Rate compression algorithm plus a new Constant Bit Rate option, then it would become much better suited for online streaming.

This post has been edited by andrewfg: Nov 22 2012, 12:07


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2Bdecided
post Nov 22 2012, 12:26
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By definition, lossless compressed formats can't be CBR.

You could "abuse" the lossyWAV algorithm to make a near-lossless CBR-ish (maybe ABR, or at least capped bitrate) encoder fairly easily.

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David.
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andrewfg
post Nov 22 2012, 22:28
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QUOTE (2Bdecided @ Nov 22 2012, 12:26) *
By definition, lossless compressed formats can't be CBR.


I don't agree. What is it about the "definition" of lossless that says it can't be CBR. Please be specific.


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Soap
post Nov 23 2012, 00:19
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QUOTE (andrewfg @ Nov 22 2012, 17:28) *
QUOTE (2Bdecided @ Nov 22 2012, 12:26) *
By definition, lossless compressed formats can't be CBR.


I don't agree. What is it about the "definition" of lossless that says it can't be CBR. Please be specific.


You were answered earlier on this very point.

QUOTE (greynol @ Nov 22 2012, 07:15) *
Name a single compressed lossless format that isn't VBR in nature.

Don't bother trying; one doesn't exist. Designing one would be futile since some signals must grow in size after being processed by a lossless compression algorithm in order for other signals to be compressible and satisfy the necessary requirement that they remain unique after being decompressed.


You can choose not to "agree" all you want, but information theory is solid math.


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andrewfg
post Nov 23 2012, 23:49
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QUOTE (Soap @ Nov 23 2012, 00:19) *
You can choose not to "agree" all you want, but information theory is solid math.


I don't dispute information theory. Indeed I am prepared to bet that I know more about the math of information theory than you do...

Nevertheless information theory has nothing to say about algorithms that can losslessly compress a data stream at a predetermined number of bytes per second. For example let us try the following algorithm: The flac encoder has nine levels of aggressivity in its compression. So let us start compressing a file at (say) grade 5. After (say) one second let us see if the compressed output is smaller or larger than our target CBR BPS. If smaller then let us back off on the compression aggressivity grade by one grade, and if larger then let us tighten the compression aggressivity by one grade. Repeat every second. So long as you are not over aggressive on choosing your target CBR BPS, then statistically speaking, you will end up with an output file that is dead on the target CBR BPS. Of course there will be Gaussian curve outliers. But, statistically this algorithm will center its statistical Gaussian peak on the selected target CBR BPS. And the longer the file, the closer it will get to the target CBR BPS...

If you want to submit some math to prove me wrong, please feel free to do so.

This post has been edited by andrewfg: Nov 24 2012, 00:25


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Posts in this topic
- andrewfg   Streaming FLAC over the Internet   Nov 22 2012, 12:06
- - greynol   QUOTE (andrewfg @ Nov 22 2012, 03:06) IMH...   Nov 22 2012, 12:15
|- - andrewfg   QUOTE (greynol @ Nov 22 2012, 12:15) Name...   Nov 22 2012, 12:19
|- - [JAZ]   QUOTE (andrewfg @ Nov 22 2012, 12:19) It ...   Nov 22 2012, 19:24
|- - andrewfg   QUOTE ([JAZ] @ Nov 22 2012, 19:24...   Nov 22 2012, 22:35
- - 2Bdecided   By definition, lossless compressed formats can...   Nov 22 2012, 12:26
|- - andrewfg   QUOTE (2Bdecided @ Nov 22 2012, 12:26) By...   Nov 22 2012, 22:28
||- - Porcus   QUOTE (andrewfg @ Nov 22 2012, 22:28) QUO...   Nov 22 2012, 23:49
||- - Soap   QUOTE (andrewfg @ Nov 22 2012, 17:28) QUO...   Nov 23 2012, 00:19
||- - andrewfg   QUOTE (Soap @ Nov 23 2012, 00:19) You can...   Nov 23 2012, 23:49
||- - Porcus   QUOTE (andrewfg @ Nov 23 2012, 23:49) Nev...   Nov 24 2012, 02:20
||- - Soap   QUOTE (andrewfg @ Nov 23 2012, 18:49) ......   Nov 24 2012, 03:44
||- - andrewfg   QUOTE (Soap @ Nov 24 2012, 03:44) Congrat...   Nov 24 2012, 14:52
|- - funkyblue   QUOTE (2Bdecided @ Nov 22 2012, 21:26) By...   Nov 23 2012, 10:45
|- - Porcus   QUOTE (funkyblue @ Nov 23 2012, 10:45) Wh...   Nov 23 2012, 11:00
|- - funkyblue   QUOTE (Porcus @ Nov 23 2012, 20:00) QUOTE...   Nov 23 2012, 11:19
|- - includemeout   QUOTE (Porcus @ Nov 23 2012, 12:00) (...)...   Nov 23 2012, 22:28
|- - funkyblue   QUOTE (Porcus @ Nov 23 2012, 20:00) QUOTE...   Nov 24 2012, 00:20
|- - andrewfg   QUOTE (funkyblue @ Nov 24 2012, 00:20) Fo...   Nov 24 2012, 00:30
|- - Wombat   QUOTE (andrewfg @ Nov 24 2012, 01:30) I a...   Nov 24 2012, 00:39
- - Nekit1234007   QUOTE (andrewfg @ Nov 22 2012, 15:06) The...   Nov 22 2012, 12:45
|- - andrewfg   QUOTE (Nekit1234007 @ Nov 22 2012, 12:45)...   Nov 22 2012, 22:31
|- - [JAZ]   QUOTE (andrewfg @ Nov 22 2012, 22:31) I a...   Nov 23 2012, 21:17
|- - andrewfg   QUOTE ([JAZ] @ Nov 23 2012, 21:17...   Nov 24 2012, 00:09
- - Porcus   If this is still relevant after [JAZ]'s clarif...   Nov 22 2012, 19:48
|- - andrewfg   QUOTE (Porcus @ Nov 22 2012, 19:48) FLAC ...   Nov 22 2012, 22:37
- - funkyblue   It is an option in dBpoweramp. http://www.audiost...   Nov 24 2012, 00:38
- - greynol   QUOTE (andrewfg @ Nov 23 2012, 14:49) If ...   Nov 24 2012, 00:58
|- - andrewfg   QUOTE (greynol @ Nov 24 2012, 00:58) Desp...   Nov 24 2012, 14:04
|- - Soap   QUOTE (andrewfg @ Nov 24 2012, 09:04) I w...   Nov 24 2012, 14:21
|- - andrewfg   QUOTE (Soap @ Nov 24 2012, 14:21) You men...   Nov 24 2012, 18:22
|- - greynol   QUOTE (andrewfg @ Nov 24 2012, 09:22) if ...   Nov 24 2012, 18:32
|- - tuffy   QUOTE (andrewfg @ Nov 24 2012, 12:22) The...   Nov 24 2012, 18:48
|- - Soap   QUOTE (andrewfg @ Nov 24 2012, 12:22) No....   Nov 24 2012, 19:20
|- - andrewfg   QUOTE (Soap @ Nov 24 2012, 19:20) That is...   Nov 25 2012, 01:10
|- - Soap   QUOTE (andrewfg @ Nov 24 2012, 19:10) Act...   Nov 25 2012, 01:29
- - funkyblue   I realise that but the link posted a bunch of cryp...   Nov 24 2012, 01:10
- - 73ChargerFan   Seeking - store a seek table in the header, say fo...   Nov 24 2012, 02:02
- - greynol   You pad and your compression goes out the window. ...   Nov 24 2012, 03:51
- - saratoga   I guess in principle you'd have to pad for at ...   Nov 24 2012, 03:55
- - greynol   If you could manage to ensure that the only data t...   Nov 24 2012, 04:00
- - Porcus   Well if you are encoding the signal in advance, yo...   Nov 24 2012, 11:36
|- - greynol   QUOTE (Porcus @ Nov 24 2012, 02:36) Well ...   Nov 24 2012, 15:24
|- - Porcus   QUOTE (greynol @ Nov 24 2012, 15:24) QUOT...   Nov 25 2012, 01:15
- - greynol   @andrewfg: Read my edit.   Nov 24 2012, 18:48
- - greynol   Axon posted a script to generate histograms and in...   Nov 25 2012, 05:39
|- - Axon   QUOTE (greynol @ Nov 24 2012, 22:39) AFAI...   Nov 25 2012, 06:34
- - 2Bdecided   I knew I should have brought popcorn.   Nov 26 2012, 14:09


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