avi2gif.bat

@echo off
:: WARNING: after some testing considered as not recommended.
:: Filter to keep only non similar frames.
:: It selects only first frame `eq(n\,0)`
:: and frames with differences `gt(scene\,{sensivity})`
:: see https://ffmpeg.org/ffmpeg-filters.html#select_002c-aselect
set similar_frames_sensivity=0.002
set skip_similar_frames=select=eq(n\,0)+gt(scene\,%similar_frames_sensivity%)

:: Adaptive Temporal Averaging Denoise.
:: https://ffmpeg.org/ffmpeg-filters.html#atadenoise
set atadenoise=atadenoise

:: Drop frames that do not differ greatly from the previous frame
:: https://ffmpeg.org/ffmpeg-filters.html#mpdecimate
set mpdecimate=mpdecimate

:: Calculate a palette
:: see https://ffmpeg.org/ffmpeg-filters.html#palettegen-1
ffmpeg -i %1 -vf "%mpdecimate%,%atadenoise%,palettegen=stats_mode=full" "%~dpn1.palette.png"

:: Transcode video to a gif with the palette
ffmpeg -i %1 -i "%~dpn1.palette.png" -lavfi "%mpdecimate%,%atadenoise%,paletteuse=dither=bayer" -y "%~dpn1.gif"

:: Cleanup
del "%~dpn1.palette.png"