FFMPEG GIF with transparency from png image sequence

Question

I've been trying to use ffmpeg to create a gif with a transparent background, but whenever the movement goes on top of the background, the pixels stay there. It's a tree with a wind animation, this is how it ends up: https://i.imgur.com/pq4ArBG.png

I first try to create the palette, and then the gif:

ffmpeg -i Tree_%04d.png -vf palettegen=reserve_transparent=1 palette.png

ffmpeg -framerate 30 -i Tree_%04d.png -i palette.png -lavfi paletteuse=alpha_threshold=128 treegif.gif

It seems the previous frames simply stay there, but I can't figure out how to dispose of them.

Answer 1

In the ffmpeg source code (libavcodec/gif.c) there are some command line flags - these are "-gifflags -offsetting", "-gifflags -transdiff" and "-gifimage". I tried these on some sample frames with transparency, and I think the first of these produces the effect you describe:

ffmpeg -i Tree_%04d.png -vf palettegen=reserve_transparent=1 palette.png
ffmpeg -framerate 30 -i Tree_%04d.png -i palette.png -lavfi paletteuse=alpha_threshold=128 -gifflags -offsetting treegif.gif