It would be really cool if we could have keyframes for this filter, especially for the hue as then we can change the hue of something and make it be rainbow, and it could work well with chroma hold. It could be that at one keyframe you have the slider set to maybe 61% (on hue) and next keyframe set it to 100% and in between that it would automatically slide over to there. This isn’t really needed but would be really cool, and would be helpful for me sometimes.
I second this.
Unfortunately, this is not possible technically because we are using FFmpeg libavfilter for this effect, which does not support keyframes for parameters. Also, we do not want to get into the habit of porting effects from libavfilter into MLT to support keyframes. We are using libavfilter sparingly for this reason. Maybe someday libavfilter will add keyframes for parameters and this will become possible, but I am going to close this for now.