gst-rtsp-server share v4l2src accross several mounting points

[jean-philippe]

Hi,

I'm trying to use gst-rtsp-server to implement an RTSP server for an IP
camera.

Here is what I need to do but have not found a way to implement:
- I am looking for a way to have several video streams running at the same
time, streaming video captured from my one v4l2 camera, but with different
encodings.
- I need to be able to add new stream/mounting points without interrupting
the streaming that may already be ongoing.
- I need to be able to capture snapshots (still images) from the camera when
0 or more RTP stream(s) are live, without interrupting the streams that may
already be live.

The v4l2src cannot be reopened, so creating individual pipelines, one for
each RTSP mounting point is not an option. So the following, based on the
GstRTSPMediaFactory does not work:
for (int i = 0; i < 2; ++i) {
   std::string s = "test_" + std::to_string(i);
   factory = gst_rtsp_media_factory_new();
   gst_rtsp_mount_points_add_factory(mounts, s.c_str(), factory)
   gst_rtsp_media_factory_set_launch(factory, "v4l2src ! vpuenc_h264 !
rtph264pay name=pay0 pt96");
   gst_rtsp_media_factory_set_shared (factory, TRUE);
}

With this sort of code, I can stream from test_1 or test_2, but not both.
The reason is that the v4l2src cannot be reopened. 

The following pipeline would work for my requirements, but according to 
this link
<http://gstreamer-devel.966125.n4.nabble.com/RTSP-Server-Can-t-get-multiple-streams-per-URI-to-work-td4672194.html>  
all streams would be sent once a client connects to the aggregate URI as
each stream does not have its own URI and must instead by filtered on the
client side based on the payload type.
This would be too inefficient for my used case and having to filter on the
payload type on the client side does not fit my requirement.

                  --> q --> fakesink (used for snapshots via last-sample)
v4l2src --> t --> q --> vpuenc_h264 --> rtph264pay name=pay0 pt=96
                  --> q --> vpuenc_h264 --> rtph264pay name=pay1 pt=97

I'm currently contemplating removing the v4l2src from the pipeline used by
the RTSP server and place it into a separate pipeline. I will then need to
somehow forward samples from that v4l2src pipeline to the pipelines used by
the RTSP server.

So something like the following:

Pipelines in my app:
   v4l2src --> appsink
   appsrc --> jpenenc --> filesink (for snapshot)

RTSP mount / pipelines:
   mount_1: appsrc --> vpuenc_h264 --> rtph264pay
   mount_2: appsrc --> vpuenc_h264 --> rtph264pay
   etc...

Then in my app, manually push samples into the appsrc elements for each
mounting points. 
This approach seems too hacky to be the right way to proceed and I am
concerned it will introduce inefficiencies (will the data be memcpy-ed when
push into the appsrc?).

So am I missing something here? Is there a simpler way to implement this?

Thanks
JP





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