[FFmpeg-user] PNGs with transparent pixels to GIF

[MediaMouth]

On Dec 20, 2020, at 11:54 AM, pdr0 <pdr0 at shaw.ca> wrote:
> 
> This has to do with gif frame disposal , and has been fixed a few months
> back. I cannot reproduce it locally.  You need up update your ffmpeg.

Frame disposal makes sense as the culprit
Turns out I'm on version 4.3.1, which I think is most recent.

There's a possibly similar issue when trying this with imagemagick...
The following will create the GIF with transparency, but will not dispose of prior frames, so as the GIF progresses the main repeats, creating a look reminiscent of a 1960s psychedelic video

convert \
PngSeq/*.png \
PngSeq.gif

And the fix is "-dispose Background"

convert -dispose Background \
PngSeq/*.png \
PngSeq.gif

The ffmpeg version in similar to the extent that 1st image (but only the 1st) image doesn't dispose, but all the subsequent images are properly disposed.  I'll continue testing.