On Sat, Jan 23, 2021 at 6:32 PM Simon Taylor <[email protected]> wrote:
> Question: Is there a way to make ffmpeg's colorchannelmixer use perceptual > gamma? > Added pl option to colorchannelmixer. It is designed to preserve overall rgb lightness. Its behavior is similar but not exact with gimp. So with your input using also pl=1 option will remove blue tint. You need latest ffmpeg build with that commit included. > > Background: I'm trying to salvage source H.264 video from a capture device > (8mm film scanner) which seems to have an extreme saturation issue that > often leaves the red and green channels saturated with minimal blue, > leaving a bright yellow stain on that area of the frame. > https://i.imgur.com/6Qh6PRk.png > > Editing a single frame capture of the video in GIMP, I see that if I use > the Colours -> Components -> Channel Mixer tool and supplement the blue > channel (1.0) with the green channel (1.0) https://i.imgur.com/Q0qqgSP.png > the result is desaturated but usable https://i.imgur.com/t19QU4U.png > > I've attempted to replicate this using ffmpeg's colorchannelmixer with the > same values (output blue = 1.0*blue + 1.0*green) > > Code: https://pastebin.com/raw/czS76ZrN > > but the result has a blue tint. https://i.imgur.com/TsnBKb2.png > > Looking at the RGB values, ffmpeg's behaviour is technically correct (the > processed B channel is an exact sum of the source B and G channels), but > GIMP's behaviour is what I need. > > GIMP's behaviour is described in > > https://graphicdesign.stackexchange.com/questions/136750/gimp-channel-mixer-does-not-work-as-expected > and gamma correction is suggested as the likely difference in how GIMP > reaches its result. > > Thanks, > > Simon > _______________________________________________ > ffmpeg-user mailing list > [email protected] > https://ffmpeg.org/mailman/listinfo/ffmpeg-user > > To unsubscribe, visit link above, or email > [email protected] with subject "unsubscribe". _______________________________________________ ffmpeg-user mailing list [email protected] https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email [email protected] with subject "unsubscribe".
