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Could we specify the codec used for decoding? #1530
Description
Line 73 in ee5c40e
It would be great if we could have a way to override this default.
For example, on my machine, I have:
$ /usr/bin/ffmpeg -hide_banner -decoders | grep h264
VFS..D h264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
V..... h264_v4l2m2m V4L2 mem2mem H.264 decoder wrapper (codec h264)
V....D h264_qsv H264 video (Intel Quick Sync Video acceleration) (codec h264)
V..... h264_cuvid Nvidia CUVID H264 decoder (codec h264)
V..... libdav1d dav1d AV1 decoder by VideoLAN (codec av1)
V....D libaom-av1 libaom AV1 (codec av1)
V....D av1 Alliance for Open Media AV1
V..... av1_cuvid Nvidia CUVID AV1 decoder (codec av1)
V....D av1_qsv AV1 video (Intel Quick Sync Video acceleration) (codec av1)
and it would be awesome to be able to change the one that is used at runtime for performance optimization based on the user's hardware.
For example there seems to be the find_decoder_by_name function
https://ffmpeg.org/doxygen/7.0/group__lavc__core.html#gad4e08a758f3560006145db074d16cb47
I'm not sure if you have a good idea for how to do this, but it would be great if it could be done! Thanks!
Activity
hmaarrfk commentedon Sep 18, 2024
PS. I know that you yourself are not using
/usr/bin/ffmpegin the package onpypibut I am integrating this with conda-forge's ffmpeg, where we do have some control over the number of shipped codecs. Most specifically, I am interested in playing with the intel QSV decoder! Thanks!jonathanhoskin commentedon Oct 7, 2024
@hmaarrfk did you ever figure this out? I am trying to solve the same problem.
hmaarrfk commentedon Oct 7, 2024
the question for me is how to specify a good API for this.
I think a good start would be get to a point wherey ou can compile PyAV yourself, and suggest a patch.
jonathanhoskin commentedon Oct 7, 2024
Oh ok. That's not my problem then. I am just trying to get PyAV to use NVIDIA CUDA hardware decoding but can't find any recent examples of how to do it.
hmaarrfk commentedon Oct 7, 2024
yes, this is what i was trying to do. you need to likely ask ffmpeg to do.
I don't think it is being done, you can likely force the
h264_nvencin the line I pointed to.The question from a library perspective, is how do you do this nicely?
MP4 is a container, you don't know what the codec is until you open it. you don't know if your hardware decoder can handle it until you read the metadata (think super tiny image).
hmaarrfk commentedon Oct 7, 2024
mind you, your ffmpeg must have been compiled with nvenc support, not sure how you are installing PyAV, but not all ffmpeg's are built equal ;)
jonathanhoskin commentedon Oct 7, 2024
Oh - I'm definitely working with a special ffmpeg build that supports cuda. If I pass the same options to PyAV it ignores them.
This CLI works:
This Python doesn't:
Am I doing it wrong?
hmaarrfk commentedon Oct 7, 2024
this is probably best for a discussion. start one. and ping me there.
please discuss how you installed both
ffmpegcommand line andpyav