[FFmpeg-user] Is libplacebo only for GPUs?

[Andrew Randrianasulu]

пт, 16 мая 2025 г., 19:26 Ferdi Scholten <ferdi at sttc-nlp.nl>:

> > Can you share ffmpeg command where you use libplacebo over opengl?
> >
> >
> >
> No, there is no such command because that is not how libplacebo is meant
> to work. Libplacebo uses the hardware abstractions that are available,
> it is not possible to specify which backend to use. It takes the best
> one available for the job depending on the hardware capabilities.
> Ultimately resorting to the dummy (cpu/software encoding) backend if
> there is no gpu capable of doing the job with OpenGL, Vulkan or DirectX.
>
> Again from the libplacebo documentation:
>
> "Every attempt was made to provide these features at a *high level of
> abstraction*, taking away all the messy details of GPU programming,
> color spaces, obscure subsampling modes, image metadata manipulation,
> and so on."
>


Well, to be honest I only imagined there *might* be way to use libplacebo
on non-vulkan capable hardware by playing video with mpv (that can use
libplacebo via opengl/directx for stuff like tonemapping and scaling) and
capture mpv's output by screen capture program.

But as you can imagine this brings question about dropped frames.

I looked into mpv on Windows 7 and there seems to be build or two still
capable of running on suc OS, see

https://github.com/mpv-player/mpv/issues/13093

more specifically build from
https://github.com/eko5624/mpv-win64/releases/tag/2024-04-29

and project I never heard before:
https://github.com/i486/VxKex

sort of compat layer for running *some* win10 software on Win7SP1

And there is also Jellyfin-ffmpeg and its SIMD Accelerated tonemapX ffmpeg
filter:

https://github.com/jellyfin/jellyfin-ffmpeg

see patches in debian folder.

I tried few vulkan/vaapi related but they not fixed lack of
interoperability between Vulkan filtering and vaapi *encoding* on my RX550.
I looked at why and it seems GFX8 gpus like my Polaris12 can't do drm
modifiers, required for inter-API surface/buffer sharing. Hw might be
capable, but whole topic is complex and no support appeared since 2018
(when this card was new) so today's chances of this code materializing seem
to be low? No Vulkan encoding either. May be this will materialize at some
time in future.

So I have all hardware blocks to do full gpu transcode *with tonemaping*,
yet graphical APIs in connection with  specific Linux drivers for this
specific card  simply does not allow me to utilize full power of hardware.

May be on Windows situation is (or was) different.


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