[Libav-user] hw filtering examples?

[Paul B Mahol]

On Thu, May 8, 2025 at 5:39 AM Andrew Randrianasulu <randrianasulu at gmail.com>
wrote:

> I am trying to find out why our (cinelerra-gg) ffmpeg integration refuses
> to load filtergraph < and crashes and burns! > if I set hw decoding to any
> value (it works for sw decoding).
>
> So far I found this example (not accepted) on ffmpeg-devel, but I am still
> not sure how to apply ot for our case (we use av_buffersink_get_frame() )
>
>
> https://ffmpeg.org/pipermail/ffmpeg-devel/2018-August/233555.html
>
> In general, I hope to get hw decoding (now via vulkan ) + libplacebo doing
> tonemapping purely on GPU *before* frames ingested into cingg for further
> (mostly software/host) manipulation, display and encode.
>
> But I guess for this I need to pass around hw_device_context created for
> decoder for this media/input file? (our filtering options are either global
> or per-file)
>
> filter_graph->filters[i]->hw_device_ctx = av_buffer_ref(hw_device_ctx);
>
> Paul, your lavfi-preview does not have hw filters previews yet, or I read
> sources too diagonally?
>

Personally, I do not use/have hw filtering (even for decoding/encoding)
enabled. The max hw that i bothered to work with was opencl and little of
vulkan.

Also I find that enabling hw stuff for filtering within ffmpeg CLI (both
OpenCL and Vulkan) is still too complex and cryptic.

The lavfi-preview build have not support code to enable any hw ctx - even
if build of ffmpeg that is used by lavfi-preview have support for it - I
never bothered to test or add support for any hw related  stuff.
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