ffmpeg - How do I convert x265 10bit to x265 8bit

Question

My media player does not support 10bit hevc content, how can I convert my 10bit hevc files to 8bit?

Solution

This will require re-encoding with thus some loss of quality but a recent copy of FFmpeg will allow you to convert to 8bit hevc from 10bit quite easily.

I tested with the following 10bit sample:

andrew@illium~$ mediainfo --Inform="Video;%Format%:%BitDepth% bits" 10_bit.mkv
HEVC:10 bits

This sample was re-encoded as follows:

ffmpeg -i 10_bit.mkv \
       -c:v libx265 -preset medium -x265-params crf=28 -pix_fmt yuv420p \
       -c:a copy \
       8_bit.mkv

The crucial option here is: -pix_fmt yuv420p. The output file demonstrated a successful conversion to 8bit:

andrew@illium~$ mediainfo --Inform="Video;%Format%:%BitDepth% bits" 8_bit.mkv
HEVC:8 bits

If you can try and avoid re-encoding in this manner though, better to encode from the original media file thus avoiding some degradation of the image and loss of quality...

References:

• Set bit depth in FFmpeg encoding for HEVC? Some more details about setting the bit depth for hevc...