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Getting NTP timestamp of RTP data

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Getting NTP timestamp of RTP data

Ingo Lütkebohle
Hi,

for synchronization of RTP streams from multiple sources, I would like to acquire the NTP timestamp of data. However, I have not found an attribute on the gstreamer buffers that would tell me this timestamp.

I have successfully retrieved the timestamp by snooping on the rtpsession's sync_src pad and decoding the sender report, so its there, but I've been wondering whether there is an easier method.

Just for clarity, this refers to cases where I am using gstreamer to receive RTP data as a client, and negotiated using RTSP.

Anything?

cheers,

--
Ingo Lütkebohle
Bielefeld University
http://www.techfak.uni-bielefeld.de/~iluetkeb/

PGP Fingerprint 3187 4DEC 47E6 1B1E 6F4F  57D4 CD90 C164 34AD CE5B

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Re: Getting NTP timestamp of RTP data

Marc Leeman
> for synchronization of RTP streams from multiple sources, I would like to
> acquire the NTP timestamp of data. However, I have not found an attribute on
> the gstreamer buffers that would tell me this timestamp.

You should read RFC 3550 again in detail.
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Re: Getting NTP timestamp of RTP data

Ingo Lütkebohle
Hi,

well, reading RFCs more thoroughly is always a good idea, but this is really a question on a gstreamer feature, so I don't quite make the connection of how that answers my question. Maybe I wasn't clear there, so: Does gstreamer makes the NTP timestamp from the sender reports available somehow as a property, or caps, or not?

btw, one more addition: My "multiple sources" are different cameras accessed via RTSP. Last I checked, gstreamer couldn't synchronize across RTSP sessions, and, anyway, I'm also interested in the absolute time-stamps for other reasons (our recording period stretches across weeks).


On Mon, Dec 10, 2012 at 4:51 PM, Marc Leeman <[hidden email]> wrote:
> for synchronization of RTP streams from multiple sources, I would like to
> acquire the NTP timestamp of data. However, I have not found an attribute on
> the gstreamer buffers that would tell me this timestamp.

You should read RFC 3550 again in detail.
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Ingo Lütkebohle
Bielefeld University
http://www.techfak.uni-bielefeld.de/~iluetkeb/

PGP Fingerprint 3187 4DEC 47E6 1B1E 6F4F  57D4 CD90 C164 34AD CE5B

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