[FFmpeg-user] overlay with video offset not starting audio with same offset

[Chad Horton]

I have a video with audio (overlayvideo.mov) that I'm overlaying over another video (basefilem.mp4) and I'm starting the overlay at 20 seconds.  The output (finalvideo.mp4) looks great, but the audio from the overlay is still starting at 00:00:00.000 instead of when I need it to start, which is 00:00:20.000 (which I set with itoffset).

I understand that itoffset only deals with video.  So, how do I go about specifying in my command below to start the audio in the overlay at the same time as itoffset?

ffmpeg -y -i basefilem.mp4 -itoffset 00:00:20.000 -i overlayvide.mov - ilter_complex "[1:v]scale=1280x720[ovrl];[0:v][ovrl]overlay=eof_action=pass[outv];[0:a][1:a]amix[outa]" -map [outv] -map [outa] -c:v mpeg4 -strict experimental -ascale:v 10 finalvideo.mp4