[FFmpeg-devel] [PATCH] lavfi: add a libplacebo filter

[James Almer]

On 3/9/2021 6:53 PM, Lynne wrote:
> Mar 9, 2021, 17:38 by ffmpeg at haasn.xyz:
> 
>> From: Niklas Haas <git at haasn.xyz>
>>
>> This filter conceptually maps the libplacebo `pl_renderer` API into
>> libavfilter, which is a high-level image rendering API designed to work
>> with an RGB pipeline internally. As such, there's no way to avoid e.g.
>> chroma interpolation with this filter, although new versions of
>> libplacebo support outputting back to subsampled YCbCr after processing
>> is done.
>>
>> That being said, `pl_renderer` supports automatic integration of the
>> majority of libplacebo's shaders, ranging from debanding to tone
>> mapping, and also supports loading custom mpv-style user shaders, making
>> this API a natural candidate for getting a lot of functionality out of
>> relatively little code.
>>
>> In the future, I may approach this problem either by rewriting this
>> filter to also support a non-renderer codepath, or by upgrading
>> libplacebo's renderer to support a full YCbCr pipeline.
>>
>> It's worth noting that this filter could be extended in the future to
>> support HWframes frames of type AV_PIX_FMT_VULKAN, but this is not
>> currently possible due to API limitations in the vulkan hwaccel.
>> (Although it's also worth pointing out that, apart from a single
>> `pl_vulkan_create` call, the current `vf_libplacebo` code does not
>> depend on vulkan at all - so in theory it could be extended to support
>> OpenGL or other libplacebo backends)
>>
> 
> Sorry, as we discussed on IRC the Vulkan hwcontext should be
> improved first and this filter should be kept as a pure hardware
> filter.

Can you explain why should it be a pure hardware filter? Why can't it be 
committed like this now, then updated to use the Vulkan hwcontext once 
you improve it?

> 
> I'm sorry, I know I've been holding up this patch for a few months,
> but could you wait until I do my job with the hwcontext? I'm already
> working on dozens of different things and I don't need extra pressure.
> Others can discuss filter options and such, but do keep in mind
> this isn't going to be the final version.
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