As mentioned in email: > From what I can tell, codecalpha is not a native VP8/VP9 decoder but a wrapper > that adds alpha blending support. Which is how it takes a colourless video and > applies the accent colour to it. This is required to implement the Matroska > 'AlphaMode' element used in the video files, which is implemented in GStreamer > by only one plugin offering the 'codec-alpha' capability.
The main difficulty in dealing with these videos is that most VP9 decoders don't understand the alpha channel and will render them incorrectly. You'll usually only see them rendered correctly in web browsers, or if you have the "bad" gstreamer plugins installed then you can use: gst-launch-1.0 filesrc location=INFILE.webm ! matroskademux ! decodebin ! glimagesink But I could not figure out how to get GStreamer to transcode, and eventually gave up on GStreamer. FFmpeg is usually more reliable and easier to work with, but it too doesn't understand the alpha channel by default: ffplay INFILE.webm But finally I figured out how to interpret the alpha channel and convert each file into greyscale (or any colour you choose): ffmpeg -c:v libvpx-vp9 -i INFILE.webm -vf alphaextract,colorize=hue=0:saturation=0:lightness=1:mix=0.5 OUTFILE.webm Please find attached some new videos that are white on grey. ** Attachment added: "greyscale-videos.zip" https://bugs.launchpad.net/ubuntu/+source/gtk4/+bug/2077117/+attachment/5813855/+files/greyscale-videos.zip -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2077117 Title: settings - mouse&touchpad - scroll direction images empty To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-control-center/+bug/2077117/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
