[FFmpeg-user] async vs. vsync or together

[Carl Eugen Hoyos]

Bernd Butscheidt <bbutscheidt <at> yahoo.de> writes:

> ffmpeg -i input.video -map 0:0 out.h264 -map 0:1,0:0 -async 48000 audio.ac3

I suspect ac3 has no timestamps, h264 has timestamps 
but they are not supported well by FFmpeg.

Apart from that: the sync options are used if the input 
stream has unusual timestamps to keep A/V sync in the 
output stream (async) or to stop FFmpeg from dropping 
or duplicating output frames (vsync) - there may be 
other uses, but I don't think above command line makes 
sense.
Note that especially the async option is less necessary 
as it used to be because FFmpeg handles many streams 
better than before even without sync options.

Carl Eugen