[Libav-user] Libavcodec D3D12 hevc_nvenc

[Ben Harper]

Have you tried just using the nvidia SDK directly? Since you need low
latency, I assume this is for some kind of realtime application, which
implies you're streaming video packets. The raw video codec data is simpler
than many people imagine. It's just a stream of packets - also called NALs,
or NALUs. The nvidia encoder will likely spit these out, and I'm guessing
this is what your decoding side needs. You'll want avcodec for packaging
those up into a .mp4 file or some other container format. But if you're
just streaming live video data, then I'm guessing you don't actually need a
container file format, so the raw packets might be good enough.

On Wed, 9 Jul 2025 at 17:12, Alex Cha <alex-1er-at-hotmail.com at ffmpeg.org>
wrote:

> Hi,
>
> I was under the impression that there was hardware acceleration for D3D12
> supported by ffmpeg.
> Upon implementing the solution however, we had unsupported pixel format
> d3d12 by the hevc_nvenc.
>
> Digging further in the nvenc.c code it seems d3d12 format is not supported
> directly. Was there a reason for this? Looking into the nvidia
> documentation the encoder should support D3D12, even if it is unclear to me
> what needs to be done.
>
> For reference, we are trying to integrate hardware streaming using FFmpeg
> into a unreal engine 5 application which uses D3D12. We need a very low
> latency.
> We have tried using the D3D11on12 interop without success, it is returning
> us "openencodesessionex failed no encode device(1)". The adapter seems to
> be using my RTX 4090 correctly but no success.
>
> Anyway, this email is a long shot in case someone as already encountered
> these issues and is able encode without copying to CPU.
>
> Thanks,
> Alex
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