[gst-devel] gstrtpbin sender multi sync receiver

[Marco Ballesio]

Hi,

another late reply ;) . See my comments below.

On Fri, Nov 12, 2010 at 10:18 AM, Thomas Roos <thomas at roosesweb.de> wrote:

> hello all,
> I want to have time synchronised audio playback (multi room feature) on
> multiple receivers (differerent ip devices)
> my sender pipeline
> alsasrc ! pcmapay ! tee ! rtpbin ! udpsink1(rtp)
>                                    !      ! udpsink1(rtcp)
>                                    !     ! udpsrc1(rtcp)
>                                    ! rtpbin ! udpsink2(rtp)
>                    ! udpsink2(rtcp)
>                  ! udpsrc2(rtcp)
>

Likely you're not using this exact command, btw I guess both the rtpbin
elements are connected to the tee.


>
> receiver pipeline 1
> udpsrc (rtp)       ! rtpbin ! pcmadepay ! alsasink
> udpsrc (rtcp)     !
> udpsink (rtcp)   !
>
> receiver pipeline 2
> udpsrc (rtp)      ! rtpbin ! pcmadepay ! alsasink
> udpsrc (rtcp)    !
> udpsink (rtcp)  !
>
> so I have tried (in order to synchronise the streams) to
> set the ts-offset in the udpsink1(rtp) to a fixed maximum network delay (i
> use WANem for testing)
>

as the timestamps are representing data generation time, I don't get how
modifying the ts-offset in the source may affect synchronisation on multiple
receivers.


> and enabled
> "ntp-sync" and "use-pipeline-clock" for the sender and receiver rtpbin
> Pipeline is working but network delay still exsists.
> Shouldn't the ntp-sync and use-pipeline clock parameter synchronize the
> sender and receiver clocks?
>

A few questions.

on a tcpdump, do you see the RTCP sender reports travelling over the
network? Setting GST_DEBUG=gstrtpbin:5, do you see messages like "NTP
time..." or "NTP diff..." on the clients? If you do, are the drift
compensations correct?

As a further point, you need to be sure that you're using the same values of
"n" for the pads you're connecting the udpsinks to in the sending pipeline
(e.g. send_rtcp_src_0 and send_rtcp_src_0).

I hope this will help.

Regards


> Together with the ts-offset it is played out delayed but synchronised? The
> ts-offset sets the playout time?
> Can anybody help me? Ideas? Examples?
> I can only find examples for lipsync audio/video streams, and that only for
> one receiver.
> According to that post:
>
> http://sourceforge.net/mailarchive/message.php?msg_id=20100827160618.15BA0EE8CE%40bugzilla-web.gnome.org
> it should work in the actual git version
> am I wrong?
> cheers Thomas
> P.S: i use the git version from 11.11.2010 of gstreamer gst-plugins-base
> gst-plugins-good
>
>
>
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