Re: [FFmpeg-user] colorchannelmixer: perceptual gamma
On Sat, 23 Jan 2021 at 21:34, Paul B Mahol wrote: > On Sat, Jan 23, 2021 at 6:32 PM Simon Taylor > 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. > Wow, that was a lot of effort to go to for what may be an obscure corner case. Thanks very much, I'll compile and test. Much appreciated! Simon ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] colorchannelmixer: perceptual gamma
On Sat, Jan 23, 2021 at 6:32 PM Simon Taylor 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 > ffmpeg-user@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-user > > To unsubscribe, visit link above, or email > ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe". ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] colorchannelmixer: perceptual gamma
On 1/23/2021 11:36 AM, Paul B Mahol wrote: Why you must always recommend alternative crappy solutions here? Why must you always dismiss anything that isn't CLI ffmpeg that might solve the user's issue? Resolve is _highly_ regarded software, and one of the better choices for colour correction. And why do dismiss these without even a hint of why they're "crappy"? And when you do dismiss an idea or suggestion, you never seem to provide an alternative. If you don't have one, then the "crappy" opinion has no weight. z! ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] colorchannelmixer: perceptual gamma
On Sat, Jan 23, 2021 at 8:29 PM Phil Rhodes via ffmpeg-user < ffmpeg-user@ffmpeg.org> wrote: > > 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'd be a little cautious about this; have you tried it on other subjects? > If it's just this clip then fine - I suspect your proposed solution is > working well because the gate is actually supposed to be white. What you've > created here is sort of a riff on very early two-colour film systems which > used red and green; they sort of work in the same way this sort of works, > giving a quasi-reasonable rendition of skin tones and foliage. > If you have other situations, though, where you have subjects that are > supposed to be just green, they'll end up cyan. I'm surprised it isn't more > visible on the plants. > I'd gently suggest that something like Resolve (free version available for > major platforms) which allows you to get creative in how and where this > stuff is applied. > Why you must always recommend alternative crappy solutions here? > P > ___ > ffmpeg-user mailing list > ffmpeg-user@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-user > > To unsubscribe, visit link above, or email > ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe". ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] colorchannelmixer: perceptual gamma
> 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'd be a little cautious about this; have you tried it on other subjects? If it's just this clip then fine - I suspect your proposed solution is working well because the gate is actually supposed to be white. What you've created here is sort of a riff on very early two-colour film systems which used red and green; they sort of work in the same way this sort of works, giving a quasi-reasonable rendition of skin tones and foliage. If you have other situations, though, where you have subjects that are supposed to be just green, they'll end up cyan. I'm surprised it isn't more visible on the plants. I'd gently suggest that something like Resolve (free version available for major platforms) which allows you to get creative in how and where this stuff is applied. P ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] colorchannelmixer: perceptual gamma
Am 23.01.2021 um 18:24 schrieb Simon Taylor: Question: Is there a way to make ffmpeg's colorchannelmixer use perceptual gamma? 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. If you know the mathematical formula, you can realize that in FFmpeg with the geq filter. But it's slow. Michael ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
[FFmpeg-user] colorchannelmixer: perceptual gamma
Question: Is there a way to make ffmpeg's colorchannelmixer use perceptual gamma? 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 ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
