[FFmpeg-devel] [PATCH 001/289 v6] Add a new channel layout API

[Marton Balint]

On Tue, 18 Jan 2022, James Almer wrote:

> From: Anton Khirnov <anton at khirnov.net>
>
> The new API is more extensible and allows for custom layouts.
> More accurate information is exported, eg for decoders that do not
> set a channel layout, lavc will not make one up for them.
>
> Deprecate the old API working with just uint64_t bitmasks.
>
> Expanded and completed by Vittorio Giovara <vittorio.giovara at gmail.com>
> and James Almer <jamrial at gmail.com>.
> Signed-off-by: Vittorio Giovara <vittorio.giovara at gmail.com>
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
> Changes since last version:
>
> *av_channel_layout_from_string() and av_channel_layout_describe() now support
> a "designation at name" syntax, effectively making both functions reciprocal
> when there are custom names in some or all channels.
> It's the syntax suggested by Marton and is both extensible if required and
> not too ulgy in human readable output if the string is printed verbatim.
>
> *av_channel_layout_index_from_string() and
> av_channel_layout_channel_from_string() also support this syntax now.

I have two suggestions. None of them is actually blocking, but since they 
concern public syntax and API it might be better to decide now.

av_channel_layout_index_from_string() without "@" in the string matches 
both builtin names (designations) and custom names. I suggest for it to 
only match builtin names. If a user wants to match by custom name, "@name" 
may be specified without a designation. This keeps the two namespaces 
separate.

av_channel_layout_channel_from_string() is an API which is not used in the 
codebase. I am not enterely sure about its purpose, so maybe it should be 
removed for now, and only added later, if some code actually needs it.

Thanks,
Marton