[FFmpeg-user] delay time in live ultrasound converter

[Michael Koch]

Hello Paul,

> ffplay and using pipe gives you huge delay. By using mpv and filtergraph
> directly you would get much lesser delay.
> Default delay introduced by this filter is the one set by win_size in
> number of samples, which is by default 4096.
> If you need less delay even than this one and can not use lower win_size
> because of lesser precision use amultiply solution which
> inherently have 0 delay.

In my test the FFT method has a shorter delay time than the amultiply 
method.
I just found out that the delay can be minimized by setting 
-audio_buffer_size to a very small value (10ms).
Delay is now about 0.5 seconds. Short enough to see and hear the bats 
simultaneously.

Michael