Enable QSV for FFmpeg with directshow input and JPEG image sequence output

Question

I'm using FFmpeg with Directshow input. The output is a series of single JPEG images. FFmpeg itself maps the stream to mjpeg and uses image2 for the output.

Is it possible to increase performance by using the Intel QuickSync Video (QSV) hardware acceleration for this process? The FFmpeg QuickSync Wiki actually lists JPEG encoding since Braswell.

This is what I tried so far:

ffmpeg -init_hw_device qsv=hw -filter_hw_device hw -f dshow -video_size 3840x2160 -framerate 25 -i "video=My Webcam" -vf hwupload=extra_hw_frames=64,format=qsv -vcodec mjpeg_qsv "C:\out\%d.jpg"

The command works, images are generated - but the GPU load seems to be the same as without any qsv options..?

Thanks!

Answer 1

I compared it for a h264 encoded video. First with the QSV jpeg encoder:

ffmpeg -c:v h264_qsv -i myvideo.mkv -vcodec mjpeg_qsv images/%06d.jpg

and afterwards without mjpeg_qsv:

ffmpeg -c:v h264_qsv -i myvideo.mkv images/%06d.jpg

The example is minimalistic and can be improved in many ways. In the picture you can see the load of the GPU. In the red box with mjpeg_qsv and the blue box without mjpeg_qsv. The execution time was also better with mjpeg_qsv, speed=3.34x vs speed=1.84x. Since you are using your webcam as an source, your pipeline is limited by the frame rate of the live video. So, your hardware will only process 25 frames per second (-framerate 25). Depending on the resolution and your hardware, this might be an easy job for your GPU, in both cases. Also, make sure you look for the Intel GPU and not your Nvidia/AMD GPU. If you still have the impression that you can't see a performance gain, please let us know both of your commands for comparison.