Am 20.09.2020 um 15:19 schrieb Michael Koch:
Am 19.09.2020 um 17:01 schrieb Paul B Mahol:
On Sat, Sep 19, 2020 at 12:10 PM Michael Koch
<astroelectro...@t-online.de>
wrote:
Hello all,
I want to create a 10-bit VLog test video which contains 18 levels of
gray, according to Panasonic's VLog curve.
The curve is documented here:
https://pro-av.panasonic.net/en/cinema_camera_varicam_eva/support/pdf/VARICAM_V-Log_V-Gamut.pdf
I want the leftmost bar to be black (128) and the other 17 bars are for
-8 to +8 stops, so that the rightmost bar is at level 1023. I'm using
this command line and the console output is copied below:
ffmpeg -f lavfi -i nullsrc=s=svga,format=gray16 -lavfi
geq=lum='st(0,trunc(18*X/W));64*(128*eq(ld(0),0)+132*eq(ld(0),1)+136*eq(ld(0),2)+144*eq(ld(0),3)+160*eq(ld(0),4)+192*eq(ld(0),5)+240*eq(ld(0),6)+298*eq(ld(0),7)+363*eq(ld(0),8)+433*eq(ld(0),9)+505*eq(ld(0),10)+578*eq(ld(0),11)+652*eq(ld(0),12)+726*eq(ld(0),13)+800*eq(ld(0),14)+874*eq(ld(0),15)+949*eq(ld(0),16)+1023*eq(ld(0),17))'
-pix_fmt yuv444p10le -crf 10 -c:v h264 -t 5 -y VLog_10bit.mov
The video looks perfect when played with FFplay. The leftmost bars are
indistinguishable on a 8-bit monitor because the levels are too close
together, but the rightmost bars look as expected.
However when I play the same video with VLC, the two brightest bars at
the right side have the same shade of gray. I don't understand why. Is
this a problem in my video, or is it a problem in VLC?
When I extraxt a 16-bit PNG image from the video, this looks as
expected
with 18 levels of gray.
ffmpeg -i VLog_10bit.mov -frames 1 -y out.png
Unrelated: I did try to add the oscilloscope filter at the end of the
filter chain, but it seems it doesn't work with 16-bit data. There
should be a warning or an error message. oscilloscope=tw=1:s=1
That happened only with gray>8 formats and have been fixed already.
Thanks, oscilloscope works fine now.
Do you have any idea why the brightest bar looks correct in FFplay and
wrong in VLC?
Is the problem reproducible on other computers?
I've solved the problem. If "-color_range pc" is added to the command
line, the video plays fine in FFplay and also in VLC.
Michael
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