ffplay doesn't correctly play files with audio timestamps not starting from 0

[Stefano Sabatini]

ffplay can't correctly plays file, where the audio timestamps doesn't start from 0.

A test file can be created with the command:

ffmpeg -f lavfi -i "flite=text='To be or not to be, that is the question',asetpts=PTS+5/TB [out0]; testsrc=n=2[out1]" -ar 16000 -acodec libmp3lame -y out.mp4

ffplay starts to play the video from the point where the audio starts, which doesn't seem the correct behavior. Compare for example with how vlc plays the file.

I don't know which is the best place to address the issue. We could add an audio pad filter, which fills the gap (but that would introduce another dependency on ffplay), or add the logic (possibly configurable) to handle that within ffplay.