Sending to ffmpeg-devel because I do not know if my workaround makes any sense? For some reason hevc alpha decoding was not working for us. I picked up https://source.ffmpeg.org/gitweb/ffmpeg.git/commit/eedf8f0165fe6523be692c5a9... avcodec/hevc: workaround hevc-alpha videos generated by VideoToolbox but videos were still not showing their alpha channel. So I added this to libavcodec/hevc/hevcdec.c: --- ./libavcodec/hevc/hevcdec.c 2026-03-16 18:13:04.000000000 +0000 +++ ./libavcodec/hevc/hevcdec.c.new 2026-05-09 05:22:45.098799320 +0000 @@ -712,9 +712,11 @@ break; } + if (alpha_fmt != AV_PIX_FMT_NONE) *fmt++ = alpha_fmt; - *fmt++ = sps->pix_fmt; + if(alpha_fmt == AV_PIX_FMT_NONE) + *fmt++ = sps->pix_fmt; *fmt = AV_PIX_FMT_NONE; // export multilayer information from active VPS to the caller, ==== basically only adding main layer (?) formats if there was no alpha) It seems to work with two hevc-alpha files and one normal hevc file May be this is only cingg specific problem - due to way we pick pixel formats on decoding? ffmpeg itself works ok without this workaround Even with this patch ffmpeg cli still picks correct format, on encoding to png: thirdparty/ffmpeg-8.1/ffmpeg -i /dev/shm/av1--test.mp4 -vframes 1 1.png 1.png contain transparency test files from https://developer.apple.com/documentation/avfoundation/using-hevc-video-with... more test files: https://lf-tk-sg.ibytedtos.com/obj/tcs-client-sg/resources/video_demo_hevc.h... possibly related https://trac.ffmpeg.org/ticket/10901 HEVC with alpha to PNG does not maintain alpha