ffmpeg xfade custom transition expression - Fetch pixel value at specifc x, y from vid1, vid2?

Question

I am using xfade with transition=custom, and trying to build expression. I am referring to official documentation https://ffmpeg.org/ffprobe-all.html#xfade

Per my understanding, expression should return pixel value of merged video

I built a few custom transitions using expressions that return some combination of A, B

For eg.,

"custom:expr='if(gt(P, abs(X/W - 0.5)), A, B)'"
"custom:expr='lerp(A, B, 1 - P)'"

For the next set of transitions, I want to fetch the pixel values from source, target video at specific positions, and combine them in my expressions

I tried using a0(X, Y), b0(X, Y) etc inside of

xfade=transition=custom:expr='r....

I ran into exceptions with ffmpeg complaining it doesn't understand the expression.

Can someone clarify, how i can fetch pixel values as specific position from source, target video and combine them in expression ?

question from:https://stackoverflow.com/questions/65882150/ffmpeg-xfade-custom-transition-expression-fetch-pixel-value-at-specifc-x-y-fr

Answer 1

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