[FFmpeg-user] Combining two audio feeds from live rtsp sources into stereo is delayed

[Mark Umansky]

> -----Original Message-----
> From: ffmpeg-user-bounces at ffmpeg.org [mailto:ffmpeg-user-
> bounces at ffmpeg.org] On Behalf Of Mark Umansky
> Sent: Wednesday, October 29, 2014 1:37 PM
> To: FFmpeg user questions
> Subject: Re: [FFmpeg-user] Combining two audio feeds from live rtsp
> sources into stereo is delayed
> 
> > -----Original Message-----
> > From: ffmpeg-user-bounces at ffmpeg.org [mailto:ffmpeg-user-
> > bounces at ffmpeg.org] On Behalf Of Carl Eugen Hoyos
> > Sent: Wednesday, October 29, 2014 12:30 PM
> > To: ffmpeg-user at ffmpeg.org
> > Subject: Re: [FFmpeg-user] Combining two audio feeds from live rtsp
> > sources into stereo is delayed
> >
> > Mark Umansky <umansky <at> torcrobotics.com> writes:
> >
> > > > >   Duration: N/A, start: 0.040022, bitrate: N/A
> > > >
> > > > If no wallclock is shown as start time here, I don't think this
> > > > can work at all.
> > >
> > > Do you mean actual real world time?
> >
> > Yes.
> >
> > > I'm not sure I follow.
> >
> > If both streams contain a "real world" start time ("wallclock time")
> > then FFmpeg should be able to synchronize them.
> > If both start with "0" then I fear synchronization will even fail
> > (sometimes) if FFmpeg were infinitely fast (which it is not).
> >
> > It may of course be a bug that FFmpeg cannot read the actual starttime
> > (that may be part of the stream), I don't know.
> >
> > Please try to fix your mailer, Carl Eugen
> 
> Assuming I can't do anything to fix the start times, is there a way to delay
> input from one of the streams so I can attempt to adjust the delay manually?
> 
> Thanks,
> Mark

Answered my own question, the "-ss" command does it nicely.

ffmpeg -y -ss 1.3 -i "rtsp://172.24.0.31:554/axis-media/media.amp?camera=1" -i "rtsp://172.24.0.32:554/axis-media/media.amp?camera=1" -filter_complex "[0:1][1:1]amerge" -vn [outputs]

-Mark