[FFmpeg-devel] [PATCH] libavcodec/mpegaudio_parser.c: differentiate MPEG audio dual mono

[James Almer]

On 12/12/2024 3:47 AM, Anton Khirnov wrote:
> Quoting James Almer (2024-11-30 14:41:20)
>> with no speaker location implied
> 
> Also, is it really the case that no speaker location is implied? I'd
> think mono (as opposed to just "1 channel") does carry the implication
> is is the center channel.

Mono, as i understand it, implies it's a single channel with the entire 
audio signal, opposed to simply "1 channel" which can be anything, even LFE.
Apple has separate values for FC and mono, and Quicktime files with one 
stream per audio channel will signal the channel meant for the center 
speaker as FC and not mono (something that affected lavf parsing of such 
files, and forced us to do some heuristics).

In practice yes, you can simplify it as mapping to FC, and in the 
absence of said speaker, just play it on FL. But there are scenarios 
where the distinction is needed, and we currently lack a way to properly 
signal this.

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