[FFmpeg-devel] [PATCH 001/279] Add a new channel layout API

[James Almer]

On 12/14/2021 9:53 AM, Nicolas George wrote:
> James Almer (12021-12-14):
>> You could attach it dynamically allocated strings too, and to prevent the
>> need for the module allocating them to outlive the layout, we could add an
>> opaque pointer to AVChannelLayout (not AVChannelCustom) and a user set
>> free() call back to pass that pointer to, on uninit().
> 
> So you want to shift the responsibility to worry about pointer lifetime
> and ownership to the API user. Sure, we can do that. We can always shift
> responsibility to API users, but that is not very nice to them.

We add a const uint8_t* field to AVChannelCustom. If the user wants to 
allocate the strings instead, and not worry about their lifetime, they 
can provide the layout with a custom free() function that will take care 
of cleaning anything they came up with on uninit().

> 
> I think the best solution would be to make this new structure
> ref-counted.

Having something like this called on every copy sounds inefficient. And 
what will you refcount? The layout? Each channel's string? Can you be 
more specific about how do you imagine implementing this?

> 
> Remember that I proposed a template to make ref-counted structures
> easily:
> https://ffmpeg.org/pipermail/ffmpeg-devel/2020-June/265227.html
> (Notice that it was soon after the first version of this API was posted:
> I was thinking of it already then.)
> 
> Regards,
> 
> 
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