Flac - Oct 2016 - Increasing number of channels?

Per https://xiph.org/flac/faq.html#general__channels currently FLAC 
supports 1 through 8 channels. This is fine for 5.1 surround sound (6 
channels). But some of the newer surround sound systems can handle many 
more channels. Is it still convenient to have all of the audio channels in 
one file for, say, a 16 channel audio track?

I don't know much about the history of FLAC. How did this many channels 
come to be the number supported? Is there any interest in increasing the 
number of channels?

Thanks for all the hard work on FLAC, I continue to get a lot of use out of 
FLAC.

The stream header only has 3 bits for the channel count, so it's not
possible to support more than 8 channels without breaking compatibility with all
embedded products that support FLAC, not to mention old and existing software.
Part of the benefit of FLAC is that it enjoys such wide support across computer
operating systems and embedded devices like audio players and digital recorders
- I'd strongly recommend against changing something this low-level just for
a little convenience for rare channel counts.

It might be worth losing compatibility with the existing installed base if there
were any real advantage to higher channel counts, but there really isn't.
FLAC can do extra compression on stereo files, such that one 2-channel FLAC can
take less space than two 1-channel FLAC files. However, the compression
advantages stop at 2 channels. There is no cross-compression with channels
beyond 2. You might as well store separate FLAC files and group them in a
directory.

Note that software like ProTools stores each channel in its own file. So, at
least the original FLAC format supports more than that. I do often take
advantage of the additional compression by converting audio recordings from dual
mono files into a single stereo file before compression.

There might still be a solution for you, though. Ogg and other formats can embed
FLAC data inside another container, so it might be possible to create a
16-channel "FLAC" in an Ogg container as two 8-channel FLAC files or
even as eight stereo FLAC files for maximum compression. I don't know
whether Ogg is optimized for streaming such that it could interleave multiple
FLAC files this way, but it's worth investigating.

Brian Willoughby
Sound Consulting


On Oct 28, 2016, at 6:24 PM, J.B. Nicholson <jbn at forestfield.org>
wrote:
> Per https://xiph.org/flac/faq.html#general__channels currently FLAC
supports 1 through 8 channels. This is fine for 5.1 surround sound (6 channels).
But some of the newer surround sound systems can handle many more channels. Is
it still convenient to have all of the audio channels in one file for, say, a 16
channel audio track?
> 
> I don't know much about the history of FLAC. How did this many channels
come to be the number supported? Is there any interest in increasing the number
of channels?
> 
> Thanks for all the hard work on FLAC, I continue to get a lot of use out of
FLAC.

Brian Willoughby wrote:
> There might still be a solution for you, though. Ogg and other formats
> can embed FLAC data inside another container, so it might be possible to
> create a 16-channel "FLAC" in an Ogg container as two 8-channel
FLAC
> files or even as eight stereo FLAC files for maximum compression. I
> don't know whether Ogg is optimized for streaming such that it could
> interleave multiple FLAC files this way, but it's worth investigating.
Thanks for the informative response, I'll look into this. I wasn't aware
any compression advantages don't extend beyond 2 channels.

Please consider switching to a mail client that respects the 
Mail-Followup-To header; I had this header set to the list address because 
I prefer to pick up my responses on the list. I don't want another copy 
sent to me as well. There are some free software mail readers that will 
respect the Mail-Followup-To header like Mozilla Thunderbird.

Thanks again for your help.