Citando Marc Lavallée <m...@hacklava.net>:

Le 2018-07-29 à 03:08 PM, Stefan Schreiber a écrit :

Citando Marc Lavallée <m...@hacklava.net>:

Excerpt from https://xiph.org/flac/faq.html#general__channels :

 "FLAC supports from 1 to 8 channels per stream. Channels are only grouped in FLAC to take advantage of interchannel correlation and to define common channel assignments (like stereo L/R, 5.1 surround, et cetera). When encoding a large number of independent channels it is expected that they are coded separately and if required, multiplexed together in a suitable container like Ogg or Matroska."

Good info.

But this is a bit typical as an “answer”: HOW would you code many channels separately in Flac (available sw to use etc.), and how to multiplex into a “suitable container”?

 Ok, no problem for anybody else... I am supposed to see! 😇

 (https://xiph.org/flac/ogg_mapping.html

They don’t explain this at all, unless you take the faq answer as a definition.)

 Best,

 Stefan

 P.S.: They just have to extend (too) old definitions.

As Fons says, the limit is a limit (paraphrasing Theresa May) - and not justified from a current perspective.

A few years ago I hacked the opusenc command line tool to encode channels without inter-channel correlation, because the correlations in the Opus codec were programmed for specific multi-channel schemes, limited to 8 channels. The "joint stereo" MP3 mode is an example of such a scheme, where channels are internally converted before encoding (see: https://en.wikipedia.org/wiki/Joint_%28audio_engineering%29).The Opus codec now have an Ambisonics mode with new inter-channel correlation schemes. I don't know if the fine Xiph developers can "just" extend the definitions of FLAC, if a special Ambisonics mode would be required, and to what extent the 8-channel limit (as a limit) is a political issue. For the multiplexing of multiple streams in a suitable container, it is left as an exercise. And if the issue is just disk space, file compression softwares (zip, gzip, etc) are still valid tools.



 Marc

- - - - -

1. I believe that the opus encoders/decoders have always supported more than 8 channels.

2. The next question is what ogg channel mapping and consequently real-world browsers allow...

But in some sense the hack you did is known. (More complicated is maybe to make it work...)

3. If they already plan to issue some ogg ambisonics standard (using ogg opus of course) since at least 2016: You also need an associated mastering standard, which would not change or compress any audio data. Correct?

So what is “political” about extending the channel count of FLAC?

Compromise proposal:

4. So let’s maybe use .wav or .caf for the “mastering format”. Microsoft and Apple already allow more than 8 channels... 🤔

Best,

Stefan

P.S.: “Joint stereo” you could classify as parametric coding.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: 
<https://mail.music.vt.edu/mailman/private/sursound/attachments/20180729/8722b963/attachment.html>
_______________________________________________
Sursound mailing list
Sursound@music.vt.edu
https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit 
account or options, view archives and so on.

Reply via email to