[FFmpeg-user] syncing live streams when mosaicing

Daniel Oberhoff daniel at danieloberhoff.de
Wed Feb 6 16:10:11 CET 2013

On 2013-02-06 11:42:30 +0000, Carl Eugen Hoyos <cehoyos at ag.or.at> said:

> Daniel Oberhoff <daniel <at> danieloberhoff.de> writes:
>> On 2013-02-06 10:01:19 +0000, Carl Eugen Hoyos <cehoyos <at> ag.or.at> said:
>>> Daniel Oberhoff <daniel <at> danieloberhoff.de> writes:
>>>> now we know the streams are time stamped correctly
>>>> using the pts (in an h264 stream).
> (Note that this sentence made me think you would
> immediately see if the pts in FFmpeg are correct or not.)
>>>> can ffmpeg
>>>> somehow use the pts to avoid the shift?
>>> Could you try to verify if FFmpeg's H264
>>> decoder actually correctly decodes the pts?
>> Ok, when I run with -loglevel debug I get outputs like this (on a
>> single stream):
> You can also use -debug_ts, it should print all
> relevant timestamp information.
> Carl Eugen

Ok, I must confess I am not so proficient in timestamps and video 
format internals. I am currenlty under the impression, that the problem 
cannot be solved the way I hoped. The streams nor the rtsp 
commnunication do not seem to contain any absolute time values (the pts 
seems to be relative to the stream start). So the only hope would be 
that ffmpeg somehow measures the stream start delays and compensates 
them. Until then we will just hope the delay is constant and compensate 
it manually.

Any better ideas?

Best, and thanks for the attention


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