How do I get a lossless recording?

[airbete]

How do I get a visual lossless recording ?

For the sake of the demonstration, I recorded a static image with vokoscreenNG (x264, quality 0). I extracted a screenshot of the .mkv file :

Here is a direct screenshot of the static image :

Finally, I also recorded the image with ffmpeg (-c:v libx264rgb -crf 0) and extracted a screenshot for comparison :

The recording with vokoscreenNG shows muddy colors and artifacts which don't show up with ffmpeg. Is there any way I get an equivalent quality with vokoscreenNG ?

Thank you.

[vkohaupt]

I could find out who caused it. It is the profile=baseline
Without this, the colors are ok.
Can you please provide the complete ffmpeg command for a better comparison.
Thanks.

[airbete]

The command is
ffmpeg -f x11grab -s 480x300 -r 30 -i :0.0 -c:v libx264rgb -crf 0 ffmpeg.x264rgb.mkv

I have also tried with huffyuv which gives a visually identical result as libx264rgb but with much bigger file size:
ffmpeg -f x11grab -s 480x300 -r 30 -i :0.0 -c:v huffyuv -crf 0 ffmpeg.huffyuv.avi

[vkohaupt]

I added a combo box with the profiles "baseline" and "high-4:4:4". "Baseline" is good for older video players and devices, but have a color sub-sampling from 4:2:0 and shows muddy colors. The "high-4:4:4" profile reproduces all colors very well, but the video player or device must support it. Vlc, mpv etc. support this.

[airbete]

Very nice! Colors look perfect now. Thank you so much.

[airbete]

I noticed today there is still something wrong.

I recorded the same static image as above with x264 / veryfast / high-4:4:4 / Quality 0.
I then played the mkv file with mpv, vlc and ffplay and recorded a screenshot in each.
Here is what I observed :
Original image == mpv == vlc != ffplay .

The recording is perfect when played with mpv and vlc, but not when played with ffplay.

This is the screenshot with mpv (identical to vlc and the original):

And this is the screenshot with ffplay:

Clearly, there is a colorspace misidentification when using ffplay. This is a problem for me as I use ffmpeg (via kdenlive) to edit my clips and they still all show wrong colors. Now, is this

• a bug in ffmpeg ?
• a bug in gstreamer (incorrect colorspace tagging) ?
• a bug in vokoscreenNG (incomplete colorspace tagging) ?

Here are some additional info:

ffplay / ffprobe
Stream #0:0(eng): Video: h264 (High 4:4:4 Predictive), yuv444p(tv, bt470bg/smpte170m/bt709, progressive), 480x300 [SAR 1:1 DAR 8:5], 30 fps, 30 tbr, 1k tbn, 60 tbc (default)
color_range=tv
color_space=bt470bg
color_transfer=bt709
color_primaries=smpte170m

mpv
[vf] [in] 480x300 yuv444p bt.601/bt.601-525/bt.1886/limited/display SP=1.000000 CL=mpeg2/4/h264
[vf] [out] 480x300 yuv444p bt.601/bt.601-525/bt.1886/limited/display SP=1.000000 CL=mpeg2/4/h264

vlc

The color_range=tv shown by ffprobe looks very strange to me. Shouldn't it be pc ? Is there any flag that can be added while recording in vokoscreenNG so that the correct colorspace will be identified by ffmpeg ?

Thank you

[vkohaupt]

I close this issue. I don't have time to search for ffplay the problem. Please understand.