[Webkit-unassigned] [Bug 181445] WebGL video texture black in Safari 11.0.2 and wrong colored in Safari Preview 11.1

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Wed Jan 10 11:20:21 PST 2018


https://bugs.webkit.org/show_bug.cgi?id=181445

--- Comment #17 from Jer Noble <jer.noble at apple.com> ---
(In reply to Klaus Reinfeld from comment #16)
> (In reply to Jer Noble from comment #15)
> > Thanks for making these test cases, this will help with debugging quite a
> > bit!  It'd also be helpful to post the command line you passed to ffmpeg to
> > generate these samples so we can reproduce the outputs with other test media.
> 
> That's the basic ffmpeg command line: 
> 
> ffmpeg -i input.mp4 -vf format=yuv420p -c:a copy output.mp4
> 
> with these parameter values as format:
> 
> yuv420p - for video range (16-235)
> yuv422p
> yuv444p
> yuvj420p - with 'j' is for full range (0-255)
> yuvj422p
> yuvj444p

Okay, I'm able to reproduce the problem with a simple SMPTE color bars example (from an image sequence). The following ffmpeg command line creates a file with the green tint problem:

ffmpeg -r 30 -f image2 -s 1920x1080 -i SMPTE_Color_Bars_16x9/%d.png -vcodec libx264 -crf 25 -pix_fmt yuvj420p test-colorspace-DEFAULT-420p.mp4

However, if you add the ffmpeg flags to make the colorspace, primaries, transfer function, and range explicit (rather than implicit from the pixel format), the color comes out correctly in a sample WebGL test:

ffmpeg -r 30 -f image2 -s 1920x1080 -i SMPTE_Color_Bars_16x9/%d.png -vcodec libx264 -crf 25 -pix_fmt yuvj420p -color_primaries bt709  -color_trc bt709 -colorspace bt709 -color_range pc test-colorspace-bt709-420f.mp4

You can verify that these metadata flags are added to the output file with mediainfo:

> mediainfo test-colorspace-bt709-420f.mp4         
...snip...
Color range                              : Full
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709

So you probably just need to make your colorspaces explicit, so that UAs can apply the correct transforms when generating RGB output.

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