[Flac] Support For More Than 8 Channels

[Martin Leese]

Chris Connaker wrote:
...
> Question: Are there any plans to increase the channel count in FLAC?

Here is a post I made to the sursound list in
2018 explaining why not:

Extending a FLAC stream beyond eight
channels is not possible.  There are two
problems; one simple, one less so:

The simple problem is that the field in the
header used for the number of channels is
only three bits.

Perhaps comparing FLAC with the Ogg
container and Vorbis codec will aid
understanding of the more difficult problem.

With Ogg, different streams can be either
chained (sequential) or grouped
(parallel/interleaved).  Typically, metadata
streams would be chained (so they appear
before any audio data) and audio streams
would be grouped.

Within a single FLAC stream the audio is
split into blocks which are grouped.  But within
each block the eight channels are chained.
This makes sense with a maximum of only
eight channels.  Within a Vorbis stream the
audio is split into frames which are grouped.
However, because a Vorbis stream can
contain up to 256 channels, within each frame
the channels are also grouped.

So the maximum of eight channels is really
embedded into the FLAC standard.  To change
this would require a whole new standard (or
the use of multiple grouped FLAC streams in
an Ogg container).

Regards,
Martin
-- 
Martin J Leese
E-mail: martin.leese  stanfordalumni.org
Web: http://members.tripod.com/martin_leese/