EnsureVBRMP3Sync
From Avisynth wiki
AviSynth+
Up-to-date documentation: https://avisynthplus.readthedocs.io
EnsureVBRMP3Sync(clip clip)
EnsureVBRMP3Sync will ensure synchronization of video with variable bitrate audio (MP3-AVI's for example) during seeking or trimming. It does so by buffering the audio. The name of the filter is a bit misleading, since it is useful for every stream with variable bitrate audio and not just for MP3.
It will slow seeking down considerably, but is very useful when using Trim for instance. Always use it before trimming.
Example:
# ensures that soundtrack is in sync after trimming
AviSource("movie.avi")
EnsureVBRMP3Sync()
Trim(250, 2500)
