SRT stream not sending

[Samuel Hurst]

Hello!

I'm experimenting with using the SRT [1] protocol and I noticed that
GStreamer has a collection of SRT elements, so I've been trying to get
them to work. However, I can't actually get any streaming to actually start.

With my distro not offering any SRT packages, I've compiled up a full
GStreamer instance from git sources (so up to date on 1.17 as of
yesterday morning) with libsrt at version 1.4.1.

As a first step, I've been following a guide from Collabora [2] to
experiment with it, and I'm using the following pipelines as server and
client respectively (on the same physical machine):

> gst-launch-1.0 videotestsrc ! video/x-raw,height=800,width=600 ! videoconvert ! x264enc tune=zerolatency ! video/x-h264,profile=high ! srtsink uri=srt://:8888/

> gst-launch-1.0 srtsrc uri=srt://127.0.0.1:8888/ ! decodebin ! autovideosink

The pipeline on both sides of the equation enter the PLAYING state, and
I can see the two peers connect and perform the handshake, but the
playback counter on the server never begins counting and I never get a
video window opening on the client side.

With GST_DEBUG="srt:9", I can see that the server seems to be stuck
waiting for a caller request after the client has "connected":

> 0:00:02.768093620 16974 0x555ed162d8f0 DEBUG  srtobject gstsrtobject.c:679:thread_func:<srtsink0> Waiting a request from caller

Reading through the code, I can't figure out how the caller is supposed
to submit a request, that will presumably kick off the sending of the
stream. The client is just sat there waiting for frames it seems.

Does anyone have any experience with these elements and might be able to
shed some light on what these problems are?


Best Regards,
Sam


[1]: https://github.com/Haivision/srt
[2]:
https://www.collabora.com/news-and-blog/blog/2018/02/16/srt-in-gstreamer/

-- 
Project R&D Engineer
BCS Internet Distribution
BBC Research and Development
5th Floor Dock House, MediaCityUK

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