tried to add this line to bin/ffmpeg/decode.opts on termux

remap_video_decoder hevc=hevc_mediacodec

it seems to work, but automatic fallback to sw decoding does not work, so you can try to remap normal h264/hevc/av1/vp9 to qsv codecs if linked with suitable (system) ffmpeg, but how well it will work depends on hw/driver.

I also created mediacodec encoders profiles for hevcand h264 - they seems to work now on ffmpeg 6.1.2. see attached git am patch

mpeg2_hdv is stray one you probably do not need - was experimenting with parameters, but without real HDV camera it a bit pointless (camera's decoder tend to be much less forgiving than sw decoder)