[FFmpeg-user] How to calculate difference between wall clock start time of audio input and wall clock start time of video input from inside the asetpts filter?

[Carl Eugen Hoyos]

2017-02-16 11:09 GMT+01:00 David Bayles <davidbayles at gmail.com>:

> Lapaki:~ Lapaki$ /Users/Lapaki/Desktop/ffmpeg -f avfoundation -video_size
> 960x540 -pixel_format uyvy422 -framerate ntsc -thread_queue_size 8B -i
> "XI:none" -f avfoundation -thread_queue_size 8B -i "none:XI" -vf
> 'crop=iw-240:ih:120:0'

> -af 'asetpts=PTS+.58735/TB'

Why is asetpts needed?
Since both input streams show useful start times, I would
have expected that this is unnecessary...

Carl Eugen