Re: Intel packages

[ja-cop <ja-cop@users.noreply.github.com>]

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New comment by ja-cop on void-packages repository

https://github.com/void-linux/void-packages/pull/41132#issuecomment-1526091256

Comment:
I tested these packages with an Intel Arc A770 with Linux 6.1.25_1, and I think I managed to get hardware accelerated video decoding working like so:
```bash
ffmpeg -hwaccel qsv -hwaccel_device /dev/dri/renderD128 -i Sprite\ Fright.mp4 \
-vcodec rawvideo -acodec copy -f matroska - | ffplay -i -
```
This works for H264, H265 and AV1 input videos. Nice! I'm not 100% sure it's not quietly falling back to software decoding, though - not sure how to reliably check. Verbose output doesn't indicate that it does.

If I replace `qsv` with `vaapi`, I get error spam:
```
Error while decoding stream #0:0: Input/output error
[h264 @ 0x562d81ba0880] Failed to end picture decode issue: 23 (internal decoding error).
[h264 @ 0x562d81ba0880] hardware accelerator failed to decode picture
```
Same errors for decoding h265 video. When passed an AV1 video, it "works", but it looks like it's falling back to the `libdav1d` software decoder without explaining why.

I haven't been able to get hardware decoding in mpv working - it looks like it doesn't support QSV, only VAAPI, at least on Linux? With `mpv --hwdec=vaapi`, it gives the same error as ffmpeg above.

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As for encoding, I think I got h264 encoding working with `-hwaccel qsv`, wasn't able to find the right parameters for h265 encode, and the AV1 encoder doesn't even show up in `ffmpeg -encoders`. I'm looking to try out [this PR for OBS](https://github.com/obsproject/obs-studio/pull/8327) to see if I can get AV1 encoding working directly from OBS without going through ffmpeg.

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Thanks for packaging these, looking forward to getting the most out of the A770 soon!