I am trying to encode a rgb input stream in real time using vaapi (so a
screen recorder). I am trying to avoid the rgb to yuv conversion on the
cpu. That works fine with 'hwupload,scale_vaapi=format=nv12' except that
the color range is incorrect. The highlights and shadows are obviously
clipped.
Here is a simple example.
# generate an input pattern as follow:
convert -negate -size 512x512 pattern:checkerboard A.png
convert -size 512x512 gradient: B.png
convert \
-negate -size 512x512 pattern:checkerboard \
-size 512x512 gradient: \
-compose Mathematics -define compose:args="0,1,0.2,-0.1" -composite \
-depth 8 -define png:color-type=2 range-pattern.png
# encode it with
ffmpeg -y -loop 1 -t 5 -i range-pattern.png -vaapi_device
/dev/dri/renderD128 -vf 'showinfo,hwupload,scale_vaapi=format=nv12'
-c:v h264_vaapi out.mkv
The pattern is completely missing in the top and bottom of the image.
That is very obvious and that looks like a range issue.
I was able to solve the problem for h264_vaapi and hevc_vaapi with
-color_range pc but that does not work for vp9_vaapi.
I know that this is not a limitation of the codec because the problem
does not exist when the yuv conversion is done before the hwupload.
I tried setting the various color options in several filters but so far
nothing is working (except doing the yuv conversion on cpu). Any idea?
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