Re: [FFmpeg-devel] [PATCH v3 1/1] avfilter/buffersink: Add video frame allocation callback

[James Almer <jamrial@gmail.com>]

On 7/23/2023 4:40 PM, Paul B Mahol wrote:
> On Sun, Jul 23, 2023 at 9:26 PM Nicolas George <george@nsup.org> wrote:
> 
>> James Almer (12023-07-23):
>>> What about when FF_FILTER_FLAG_HWFRAME_AWARE filters are present in the
>>> graph? hw_frames_ctx from AVFilterLink can't be accessed from outside
>> lavfi.
>>> Is vf_hwdownload meant to be added to the graph before buffersink?
>>
>> I do not know how hardware acceleration works at all. (The tidbits of
>> discussion I catch left me the impression all of it is very badly
>> designed, but I have low confidence in that impression.) If this API
>> only works with filters that output software frames, it is already very
>> useful.
>>
> 
> Patch is only marginally useful:
> 
> - missing audio support

Trivially added if needed and when needed. alloc_cb is a union that can 
get a new callback typedef field for audio.

> - missing full internal buffers allocation replacement support

What is the benefit of supporting a custom allocator for all filters in 
the chain? Internally, it's already using a very optimized buffer pool. 
The caller only cares about how what they get out of buffersink is 
allocated.


> - missing/untested hardware acceleration support

This however i agree about. We need to know how it will behave in this 
scenario. How does buffersink currently handle things when the previous 
filter in the chain propagates hardware frames?

> 
> 
>> Regards,
>>
>> --
>>    Nicolas George
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