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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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greynol
post Nov 22 2012, 12:15
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QUOTE (andrewfg @ Nov 22 2012, 03:06) *
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.

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.

This post has been edited by greynol: Nov 22 2012, 12:51


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andrewfg
post Nov 22 2012, 12:19
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QUOTE (greynol @ Nov 22 2012, 12:15) *
Name a single compressed lossless format that isn't VBR in nature.


There aren't any.
It is true: all current compressed lossless formats suck, as far as Http streaming is concerned.


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[JAZ]
post Nov 22 2012, 19:24
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QUOTE (andrewfg @ Nov 22 2012, 12:19) *
It is true: all current compressed lossless formats suck, as far as Http streaming is concerned.


Definitely, this thread has gone offtopic, but your comments require an answer.

First:
Stream: a continuous (once received) set of data. Generally speaking, a set of data that is being transmitted from a source to a destination.

When the set of data has a determined size, then, it rarely is called stream, but a download or upload.
In other words, streams in internet tend to be of data for which the size is not determined. One such example is, obviously, a Live radio stream.

Second:
The HTTP ContentLength header can have the value of 0, which tells the browser that the size of the stream is not known beforehand.

In our job, we generate PDF files in realtime, and in some cases, start sending them before the file is fully generated (Like for files that can have several megabytes). In such cases, the file size is undetermined and, as such, the ContentLength that we send is zero.

This post has been edited by [JAZ]: Nov 22 2012, 19:26
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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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