[Libav-user] Retrieving absolute timestamps from IP cameras

Andy Shaules bowljoman at gmail.com
Tue Nov 26 19:39:11 CET 2013

On 11/26/2013 12:34 AM, Dídac Pérez wrote:
> Hi all,
> I am using ffmpeg C++ libraries for connecting to network IP cameras 
> and retrieve the video stream through RTSP. I need to synchronize the 
> video frames to another video stream whose frames have timestamps that 
> come from a GPS signal. The problem is that I am not able to find the 
> absolute timestamp of the frames I get from the cameras. pts/dts 
> values are zero-based relative to the first frame, but I don't know 
> how to know the absolute timestamps (for instance, relative to 1 Jan 
> 1900). In addition, I don't know if it is actually possible.
> Please, I am stuck in this point and I need urgent help with this, and 
> I will really appreciate any help from you. Thank you so much.
> Kindest regards,
> Dídac Pérez
> _______________________________________________
> Libav-user mailing list
> Libav-user at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/libav-user
RTCP Sender Reports can be used and ip cams usually include them 
in-band. http://tools.ietf.org/html/rfc3550#section-6.4.1

THe camera manufacturer should have more info on setting up a local 
network clock for the cameras to sync their clocks to.

Using Axis? they have so much documentation that you can accomplish 
everything you can imagine.


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