https://source.ffmpeg.org/gitweb/ffmpeg.git/commit/eedf8f0165fe6523be692c5a9... I saved this patch and applied to our ffmpeg. Now ffmpeg itself correctly decodes puppets_with_alpha_hevc.mov file from test project at https://developer.apple.com/documentation/avfoundation/using-hevc-video-with... thirdparty/ffmpeg-8.1/ffmpeg -i /dev/shm/HEVC-Videos-With-Alpha-Exports/Resources/puppets_with_alpha_hevc.mov -vframes 1 1.png but in cinelerra-gg I still have fully-black background (prores sample from same project works ok)