M4V is just an alias for MP4.
So you can use ffmpeg to copy the audio/video streams in your AVI file to a more recent MP4 container:
ffmpeg -i source.avi -f mp4 -vcodec copy -acodec copy destination.mp4
M4V is just an alias for MP4.
So you can use ffmpeg to copy the audio/video streams in your AVI file to a more recent MP4 container:
ffmpeg -i source.avi -f mp4 -vcodec copy -acodec copy destination.mp4