RTP/RTSP Camera Capture Timestamping

[Joshua Quesenberry]

Good Afternoon All,

 

I'm looking into IP cameras right now and trying to understand how to
accurately determine when a frame was captured. Hopefully some of you all
have dealt with this and can give me some guidance? I have a couple
different scenarios, each of which I want to be able to know the UTC time of
when the frame was captured by the camera or at the very least when the
packet hits a Linux box's kernel.

 

Scenario 1: USB Camera -> Linux Box 1 via v4l2src.

 

Scenario 2: USB Camera -> Linux Box 1 via v4l2src -> Network via rtpbin
(RTP/RTCP) -> Linux Box 2 via rtpbin.

 

Scenario 3: GigE Camera RAW Stream -> Linux Box 1 via The Imaging Source
element (tcamsrc).

 

Scenario 4: GigE Camera RAW Stream -> Linux Box 1 via The Imaging Source
element (tcamsrc) -> Network via rtpbin (RTP/RTCP) -> Linux Box 2 via
rtpbin.

 

Scenario 5: IP Camera H264 Stream with NTP Sync every 60min -> Linux Box 1
via rtspsrc element.

 

Scenario 6: IP Camera H264 Stream with NTP Sync every 60min -> Linux Box 1
via rtspsrc element -> Network via rtpbin (RTP/RTCP) -> Linux Box 2 via
rtpbin.

 

Is what I'm looking for possible in all of these scenarios?

 

When using the timeoverlay element, when are time-mode ==
elapsed-running-time (4) and time-mode == reference-timestamp (5) available?

 

When using the identity element with silent=false, is there a way to print
to the screen the content of GstBuffers meta data? Seems like from reading
this may contain some time elements I'd be interested in?

 

Can RTP/RTCP/RTSP propagate UTC capture time information or does it get lost
early on in the pipeline across multiple Linux boxes?

 

All of my systems and the IP Cameras above should be looking at a local NTP
Server instance at this point, so hopefully that will help things? It looks
like the GigE cameras can't talk to an NTP server.

 

Thanks!

 

Josh Q

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