[FFmpeg-devel] Howto utilize GPU acceleration outside expected places?

[martin schitter]

On 10.10.24 08:06, Lynne via ffmpeg-devel wrote:
> You can copy libavutil/vulkan* into whatever project you want, and 
> change 4 #include lines to make it compile.
> This lets you use the same API to construct and execute shaders as you 
> would within lavc/lavfi/lavu into your own project. You will need to 
> make libavutil a dependency as hwcontext_vulkan.c cannot be exported and 
> must remain within libavutil.

Thanks for this description and the link. It's very interesting but not 
exactly the kind of utilization I'm looking for.

I don't want to use the ffmpeg vulkan utils in another application, as 
demonstrated in your example. I just want to use it within ffmpeg 
itself, but slightly different as in all places which I saw until now.

To bring it to the point:

I would like to accelerate this trivial 10 and 12bit decoding of 
bit-packed-scanlines in my DNxUncompressed implementation using compute 
shaders, whenever the required hardware support is available resp. was 
enabled on startup and fallback to CPU processing otherwise.

This is a different usage scenario than utilizing the hardware encoding 
and decoding facilities provided by vulkan, which seem to be the only 
kind of vulkan related GPU utilization in libavcodec until now.

And because it should be used automatically if available and otherwise 
fall back to CPU processing it also differs significantly from the 
vulkan- and placebo filters, which are strictly divided from their CPU 
counterparts and don't provide any fallback.

I simply couldn't find any location in ffmpegs source code, which looks 
close to this vague idea. Perhaps it's simply impossible for one or the 
other reason that I do not see -- who knows?

I would be happy if you could possibly point me to already existing 
relevant code in ffmpeg to learn how to develop this kind of behavior as 
efficient as possible.

thanks
martin