FFmpeg で h264_qsv やるとエラーとなることがあります。
ffmpeg -i sintel_trailer-1080p.mp4 -vcodec h264_qsv out_qsv.mp4
failed!
[h264_qsv @ 0x35a2420] No device available for encoder (device type qsv for codec h264_qsv). [h264_qsv @ 0x35a2420] Selected ratecontrol mode is not supported by the QSV runtime. Choose a different mode. Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height [aac @ 0x35d60e0] Qavg: 148.307 [aac @ 0x35d60e0] 2 frames left in the queue on closing Conversion failed!
オプションとして -init_hw_device qsv:hw を付けると良さそうです。
ffmpeg -i sintel_trailer-1080p.mp4 -vcodec hevc_qsv -init_hw_device qsv:hw out_qsv.mp4
#6492
Intel QSV: "No device available for encoder" message is given
https://trac.ffmpeg.org/ticket/6492