[FFmpeg-user] delay time in live ultrasound converter

Michael Glenn Williams michael.glenn.williams at smartblondeco.com
Sat Apr 18 17:52:49 EEST 2020


The subject line about ultrasound caught me eye on this thread that woke up
from last year.
Can anyone tell us what the original interest in ffmpeg and ultrasound is?

Thank you!

On Fri, Apr 17, 2020 at 3:55 PM Roger Pack <rogerdpack2 at gmail.com> wrote:

> On Thu, Aug 22, 2019 at 3:16 PM Michael Koch
> <astroelectronic at t-online.de> wrote:
> >
> > 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.
>
> Se also https://trac.ffmpeg.org/wiki/DirectShow#BufferingLatency
> GL! :)
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