>>508
-bsf:v h264_metadata=matrix_coefficients=1

FFmpeg Bitstream Filters Documentation 2.6 h264_metadata
https://ffmpeg.org/ffmpeg-bitstream-filters.html#h264_005fmetadata

matrix_coefficientsの値
1: BT.709
6: BT.601(smpte170m)
9: BT.2020nc