ffmpeg using wrong default colorspace for HEVC

[Jozef Chutka]

Using FFmpeg with hevc_videotoolbox and default colorspace will create output with a wrong colorspace:

ffmpeg -i premultiplyTest_png_256x256_0MB.png -vcodec hevc_videotoolbox -r 1 -t 1 -vtag hvc1 -alpha_quality 1 -y out1.mp4

Here is the related issue raised with the chrome team for why rendered HEVC colors are washed:

​https://issues.chromium.org/issues/342003180#comment20

"encode video with an extra -colorspace 13 command, since if you don't specify this, ffmpeg will write wrong colorspace matrix info into SPS and container."

I can confirm using adding -colorspace 13 produces output which renders ok in chrome.

ffmpeg -i premultiplyTest_png_256x256_0MB.png -vcodec hevc_videotoolbox -r 1 -t 1 -vtag hvc1 -alpha_quality 1 -colorspace 13 -y out2.mp4

I wonder if this is something to fixed in ffmpeg?