[FFmpeg-user] Merge two RTSP inputs into one TS stream

[Moritz Barsnick]

On Thu, May 26, 2016 at 14:20:31 -0400, Wu-bin Zhen wrote:
> I used ffmpeg command like "ffmpeg -i rtsp://<encoder1> -i
> rtsp://<encoder2> -c copy -y filename.ts", and noticed that the second
> track in the ts file is always 2-3 seconds behind.

I think that this is due to the fact that ffmpeg uses its (receiving)
wallclock time as a time base, and this seems to differ for multiple
streams, due to startup time. ffmpeg *does* use the sender's timestamps
for calculating the frame time *differences*, for use in calculating
PTS.

ffmpeg should evaluate and forward the sender's timestamp, which
*might* allow synchronizing these streams. I was involved in a
discussion about that here, but I think no patch was ever submitted:

https://ffmpeg.org/pipermail/ffmpeg-user/2016-March/031250.html

Moritz