[Libav-user] Retrieving absolute timestamps from IP cameras

Dídac Pérez perez.didac at gmail.com
Wed Nov 27 09:25:42 CET 2013

Hi Andy, thank you so much for your answer. I will ask Axis about how to
set up the local clock. However, I don't know how to get that timestamps
using ffmpeg. Maybe I am quite noob in streaming protocols. Could you
please give me more details about it? For instance: does each AVPacket
contains that timestamp? or AVFormatContext? I am quite confused.

Dídac Pérez

2013/11/26 Andy Shaules <bowljoman at gmail.com>

>  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 listLibav-user at ffmpeg.orghttp://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.
> Andy
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> Libav-user at ffmpeg.org
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