Transmit absolute time

Pietro Bonfa' pietro_bonfa at
Sun Oct 18 11:19:20 PDT 2015

On 10/16/2015 03:28 PM, Sebastian Dröge wrote:
> On Do, 2015-10-15 at 11:42 +0200, Pietro Bonfa' wrote:
> Let us know if you run into any problems or have further questions :)

At the present stage I'm trying to understand the structure of rtp
plugins that are in gst-plugins-good in order to insert
gst_rtp_buffer_get/set_extension, gst_rtp_buffer_get/set_extension_data
and gst_rtp_buffer_get/set_extension_bytes somewhere.

Readings, suggestions and/or examples are welcome.

> So you mean that the frame grabbers are not producing a frame at 0.025
> second boundaries but somewhere around that? And you want all frame
> grabbers to produce a frame at exactly N*0.025 seconds, i.e. all of
> them at the same time?

No. Frame-grabbers are not perfect so they produce frames at

N.025+epsilon1, N.050+epsilon1, ...
N.025+epsilon2, N.050+epsilon2, ...

This is out of my control, but I have timestamps.

What I wanted to clarify is that if I use two pipelines like in RTSP
net-clock-client code for receiving the two streams (from two different
servers), they are indeed synchronized but I'm missing a way to estimate
epsilon1 from pipeline1 and epsilon2 from pipeline2.


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