#7965: Support for HEVC with Alpha -------------------------------------+----------------------------------- Reporter: leemartin | Owner: (none) Type: enhancement | Status: open Priority: wish | Component: avcodec Version: git-master | Resolution: Keywords: hevc | Blocked By: Blocking: | Reproduced by developer: 0 Analyzed by developer: 0 | -------------------------------------+----------------------------------- Comment (by logiclrd):
As I understand x265 does not support alpha
It does now. As of version 4.0, which dropped a month or two back, there is a `--alpha` command-line option. With this option, the input is assumed to be a `yuva420p` raw stream. As of writing this, to get this latest version you must build `x265` from source. At least on my OS, the central package manager doesn't yet have version 4.0. I have found the following sequence which //seems// to produce an MP4 file with HEVC with alpha content, but I am not on a Mac and have found no way to test it because the decoding support described by this ticket is not yet implemented. :-) {{{ x265 --input-res 606x692 --fps 30000/1001 --alpha --crf 20 Zap.yuva420p Zap.hevc mkvmerge Zap.hevc -o Zap.mkv ffmpeg -itsscale 0.3336666666 -i Zap.mkv -c copy -vtag hvc1 Zap.mp4 -y }}} The `-itsscale` option is to fix an issue with the framerate. I couldn't find a way to get `mkvmerge` to produce the right output (there may be a way). By default, it seems to emit HEVC frames timestamped to 10fps. This scale factor converts from 10fps to 30000/1001 fps. Hopefully this information is helpful to someone. There is a tool called Zond 265 which does some fascinating inspection of internal H.265 encoding details. It does not support alpha channels yet, and I was told that the reason is that FFMPEG doesn't decode HEVC with Alpha yet. I also found this related issue in Trac: #10901 (Does Trac have a mechanism for relationships between tickets?? A quick web search suggests that the answer is //Yes//, but only if you use an unmaintained plugin called `TracTicketReferencePlugin`...) -- Ticket URL: <https://trac.ffmpeg.org/ticket/7965#comment:14> FFmpeg <https://ffmpeg.org> FFmpeg issue tracker