[flac-dev] Fwd: Re: Flac multi channel

Federico Miyara fmiyara at fceia.unr.edu.ar
Thu Jan 26 01:30:06 UTC 2017

-------- Forwarded Message --------
Subject: 	Re: [flac-dev] Flac multi channel
Date: 	Wed, 25 Jan 2017 15:55:14 -0300
From: 	Federico Miyara <fmiyara at fceia.unr.edu.ar>
To: 	Tor-Einar Jarnbjo <tor-einar at jarnbjo.name>

Besides the fact that many multichannel signals largely exceed 8 
channels, there are examples of signal packaging with many channels 
which are actually non-simultaneous, independent signals, for instance 
the CIPIC HRTF (or more properly, HRIR) database, which would benefit 
from FLAC packaging.

The file format allows some unused fields for future use, such as the 
padding block. It could include a flag to indicate a change in the 
format adding one more streaminfo byte which would allow up to 256 
channels (actually, 256 + 8), or it could trigger a new byte when 11111111.

There is also an invalid block identifier (127) which could be used with 
the same purpose.

Old versions of the reference codec (or third-party implementations) 
would not be able to open new flac files with more than 8 channels but 
the "old" format could be still opened with the new versions.



On 25/01/2017 14:30, Tor-Einar Jarnbjo wrote:
> Hello Olivier,
> the limitation is in the file format itself, as the number of channels 
> is encoded in a 3 bit field in the streaminfo metadata block.
> Tor-Einar
> Am 25. Januar 2017 16:45:32 MEZ schrieb Olivier Tristan 
> <o.tristan at uvi.net>:
>     Hi Guys,
>     I know that FLAC format is currently limited to 8 channels but I was
>     wondering if this hard limitation of the format
>     or if it can be easily circumvented if the flac library is compiled with
>     other settings and/or the software using it don't mind it
>     Thanks !
> _______________________________________________
> flac-dev mailing list
> flac-dev at xiph.org
> http://lists.xiph.org/mailman/listinfo/flac-dev

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