[flac-dev] Flac multi channel

Brian Willoughby brianw at audiobanshee.com
Wed Jan 25 20:09:27 UTC 2017

For one thing, only stereo files benefit from additional compression by taking advantage of similar audio in the two channels. FLAC files with more than two channels are not any more efficient than separately-compressed monophonic files. In fact, depending upon the audio content, you're probably better off encoding an eight-channel set as four stereo FLAC files, even though FLAC supports eight-channel files already.

At a certain point, you have to put a limit on block sizes to accommodate embedded devices, not to mention the streaming latency of large data sets. As you cram more channels into a block, you get fewer samples per block for each individual channel. There simply isn't any advantage to having lots of channels in a single stream.

I believe that Ogg allows you to create a file that interleaves multiple FLAC files. So, if you want high channel counts then it seems like FLAC in Ogg is the choice (but I have not experimented with this option, personally).

Brian Willoughby
Sound Consulting

On Jan 25, 2017, at 11:27 AM, Olivier Tristan <o.tristan at uvi.net> wrote:
> I see :(
> That what I would call a good struct size optimisation. 
> Please tell me there was another reason behind this being only 3 instead of 8 or 16 bits, right ?
> 2017-01-25 18:30 GMT+01:00 Tor-Einar Jarnbjo <tor-einar at jarnbjo.name>:
>> 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

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