On 12/16/2021 9:04 PM, Marton Balint wrote:
On Thu, 16 Dec 2021, James Almer wrote:
Resending the first two patches only, since this is meant to
show the implementation of one of the several suggestions made
in the previous set that need to be discussed and hopefully
resolved in a call.
Can you push the full branch somewhere?
Just force pushed the latest version to the same repo as last time in
https://github.com/jamrial/FFmpeg/commits/channel_layout
The proposals so far to extend the API to support either custom
labels for channels are, or some form of extra user information.
- Fixed array of bytes to hold a label. Simple solution, but
the labels will have a hard limit that can only be extended
with a major bump. This is what i implemented in this version.
- "char *name" per channel that the user may allocate and the
API will manage, duplicate and free. Simple solution, and the
name can be arbitrarily long, but inefficient (av_strdup() per
channel with a custom label on layout copy).
- "const char *name" per channel for compile time constants, or
that the user may allocate and free. Very efficient, but for
non compile time strings ensuring they outlive the layout can
be tricky.
- Refcounted AVChannelCustom with a dictionary. This can't be
done with AVBufferRef, so it would require some other form
of reference counting. And a dictionary may add quite a bit of
complexity to the API, as you can set anything on them.
Until we have proper refcounting API we can make the AVBufferRef in
AVChannelLayout a void *, and only allow channel_layout functions to
dereference it as an AVBufferRef. This would mean adding some extra
helper functions to channel layout, but overall it is not unsolvable.
The real question is that if you want to use refcounting and add helpers
to query / replace per-channel metadata, or you find the idea too heavy
weight and would like to stick to flat structs.
- Opaque id/s or pointer/s that the API will not touch beyond
passing them around (So unlike the above, the helpers would not
benefit from this). This can be combined with any of the above,
too, and i did as much in this version.
- Leave API as it was in v1.
Maybe it is not said enough times, but thanks to everybody who worked on
this. It certainly was huge work, and I know that it is a thankless
effort to get such a big change merged. Any change based on my
suggestions is appreciated, even if some of my ideas get rejected in the
end.
Thanks,
Marton
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