[FFmpeg-user] Clarification for decoding AV1 input on the GPU

[Mario Roy]

Thank you, Haihao. I applied the patchset to FFmpeg 5.1 branch.  Passing
-hwaccel {nvdec|vdpau} without -c:v av1 still decoded on the CPU. I double
checked to be sure the patchset was applied.

I obtained AV1 and VP9 samples via yt-dlp: 1920x1080 resolution.

$ yt-dlp -F https://youtu.be/mIAfxj7nd9k
$ yt-dlp -f 399 https://youtu.be/mIAfxj7nd9k -o input_av1.mp4
$ yt-dlp -f 248 https://youtu.be/mIAfxj7nd9k -o input_vp9.webm

Hardware: GeForce RTX 3070 FE

AV1 Observations.

$ ffmpeg -y -hwaccel nvdec -c:v av1_cuvid -i input_av1.mp4 output.ts   #
GPU fps=653
$ ffmpeg -y -hwaccel vdpau -c:v av1_cuvid -i input_av1.mp4 output.ts   #
Core Dumps
$ ffmpeg -y -hwaccel nvdec -c:v av1 -i input_av1.mp4 output.ts         #
GPU fps=454
$ ffmpeg -y -hwaccel vdpau -c:v av1 -i input_av1.mp4 output.ts         #
GPU fps=246
$ ffmpeg -y -hwaccel nvdec -i input_av1.mp4 output.ts                  #
CPU libdav1d
$ ffmpeg -y -hwaccel vdpau -i input_av1.mp4 output.ts                  #
CPU libdav1d

VP9 Observations.

$ ffmpeg -y -hwaccel nvdec -c:v vp9_cuvid -i input_vp9.webm output.ts  #
GPU fps=669
$ ffmpeg -y -hwaccel vdpau -c:v vp9_cuvid -i input_vp9.webm output.ts  #
Core Dumps
$ ffmpeg -y -hwaccel nvdec -c:v vp9 -i input_vp9.webm output.ts        #
GPU fps=662
$ ffmpeg -y -hwaccel vdpau -c:v vp9 -i input_vp9.webm output.ts        #
GPU fps=529
$ ffmpeg -y -hwaccel nvdec -i input_vp9.webm output.ts                 #
GPU fps=655
$ ffmpeg -y -hwaccel vdpau -i input_vp9.webm output.ts                 #
GPU fps=533

Looking at the AV1 results, -hwaccel vdpau -c:v av1 is nearly 2x slower
than -hwaccel nvdec -c:v av1.

Should FFmpeg exit gracefully if passing unsupported options for -hwaccel
vdpau? Or is this a bug?
-hwaccel vdpau -c:v av1_cuvid  # Crashes
-hwaccel vdpau -c:v vp9_cuvid  # Crashes

Thanks,
Mario

On Tue, Jul 19, 2022 at 8:42 PM Xiang, Haihao <
haihao.xiang-at-intel.com at ffmpeg.org> wrote:

> On Tue, 2022-07-19 at 16:54 -0500, Mario Roy wrote:
> > Greetings,
> >
> > With the recent FFmpeg 5.1 supporting AV1 using VDPAU, should decoding
> AV1
> > occur on the GPU automatically (NVIDIA 3000 series), similarly to
> decoding
> > VP9?
> >
> > ffmpeg -y -hwaccel vdpau -i input_av1.mp4 output.ts   # decodes on the
> CPU
>
>
> libdav1d has higher priority than the the native av1 decoder in FFmpeg, you
> should specify the native av1 in your command line if you want to use
> vdpau.
>
> $ ffmpeg -y -hwaccel vdpau -c:v av1 -i input_av1.mp4 output.ts
>
> Or you may try
>
> https://patchwork.ffmpeg.org/project/ffmpeg/patch/20210922074207.19451-2-haihao.xiang@intel.com/
>  which can decode AV1 on the GPU automatically when -hwaccel xxx is
> specified in
> the command line. (You need to rebase the patchset).
>
> Thanks
> Haihao
>
>
> > ffmpeg -y -hwaccel vdpau -i input_vp9.webm output.ts  # decodes on the
> GPU
> >
> >  Are the following incorrect usage? Both segfaults.
> >
> > ffmpeg -y -hwaccel vdpau -c:v av1_cuvid -i input_av1.mp4 output.ts   #
> > segfaults
> > ffmpeg -y -hwaccel vdpau -c:v vp9_cuvid -i input_vp9.webm output.ts  #
> > segfaults
> >
> > Thanks,
> > Mario
> >
> > On Wed, Jul 13, 2022 at 9:44 AM Mario Roy <marioeroy at gmail.com> wrote:
> >
> > > Hi,
> > >
> > > What are the recommended arguments for folks using NVIDIA 3000 series
> > > graphics and decoding AV1 media? I tried the same with VP9 media.
> > >
> > > The following was done using FFmpeg 5.1.
> > >
> > > ffmpeg -y -hwaccel vdpau -c:v av1_cuvid -i input_av1.mp4
> > > output.ts   segfaults
> > > ffmpeg -y -hwaccel vdpau -c:v vp9_cuvid -i input_vp9.webm
> > > output.ts  segfaults
> > >
> > > ffmpeg -y -hwaccel vdpau -i input_av1.mp4 output.ts   decodes on the
> CPU
> > > ffmpeg -y -hwaccel vdpau -i input_vp9.webm output.ts  decodes on the
> GPU
> > >
> > > ffmpeg -y -hwaccel nvdec -c:v av1_cuvid -i input_av1.mp4 output.ts
> > > ffmpeg -y -hwaccel nvdec -c:v vp9_cuvid -i input_vp9.webm output.ts
> > >
> > > ffmpeg -y -c:v av1_cuvid -i input_av1.mp4 output.ts
> > > ffmpeg -y -c:v vp9_cuvid -i input_vp9.webm output.ts
> > >
> > > Best,
> > > Mario
> > >
> > >
> >
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