Problems with multicast RTSP stream if no default gateway is defined

Thu Sep 17 15:59:51 UTC 2020

Hello Nicolas,

El jue., 17 sept. 2020 a las 17:00, Nicolas Dufresne
(<nicolas at ndufresne.ca>) escribió:
>
> Le jeudi 17 septembre 2020 à 15:03 +0200, Guillermo Rodriguez Garcia a
> écrit :
> > Hi all,
> >
> > I am trying to play a multicast RTSP stream using GStreamer and I am
> > seeing some unexpected behaviour. This is a simplified version of the
> > pipeline I am using:
> >
> > gst-launch-1.0 rtspsrc location=rtsp://192.168.0.216 ! rtph264depay !
> > avdec_h264 ! videoconvert ! videoscale ! fakesink
> >
> > The RTSP source and the machine running GStreamer are both in an
> > isolated LAN (192.168.0.xxx). There is no "default gateway" defined.
> >
> > The above pipeline results in errors ("Error joining multicast group:
> > No such device").
>
> I believe you are missing a route that would tell your system which
> network interface to use. If I'm right, you can solve this using
> `multicast-iface` property. The iface name is platform specific, you
> will need your own code to find it.

Yes, that's what I thought too (it was described in the second part
of my email). I tried to pass multicast-iface=.. to rtspsrc:

gst-launch-1.0 rtspsrc multicast-iface=enp0s3 ! ....

But this doesn't work either, although a different error is reported:

[...]
Progress: (open) Opened Stream
Setting pipeline to PLAYING ...
New clock: GstSystemClock
Progress: (request) Sending PLAY request
Progress: (request) Sending PLAY request
0:00:00.154308014  [335m 3790 [00m 0x7fdd44031a30  [33;01mWARN    [00m
 [00m        multiudpsink
gstmultiudpsink.c:686:gst_multiudpsink_send_messages:<udpsink0> [00m
warning: Error sending UDP packets
0:00:00.154344693  [335m 3790 [00m 0x7fdd44031a30  [33;01mWARN    [00m
 [00m        multiudpsink
gstmultiudpsink.c:686:gst_multiudpsink_send_messages:<udpsink0> [00m
warning: client 239.0.0.1:5000, reason: Error sending message: Network
is unreachable
WARNING: from element
/GstPipeline:pipeline0/GstRTSPSrc:rtspsrc0/GstUDPSink:udpsink0: Error
sending UDP packets
Additional debug info:
../gst/udp/gstmultiudpsink.c(686): gst_multiudpsink_send_messages ():
/GstPipeline:pipeline0/GstRTSPSrc:rtspsrc0/GstUDPSink:udpsink0:
client 239.0.0.1:5000, reason: Error sending message: Network is unreachable

That's the part I don't understand. If I explicitly specify an interface to use
for multicast, that should be enough, shouldn't it ?

Thanks,

Guillermo

>
> >
> > [...]
> > 0:00:00.146730467  [333m 2432 [00m 0x55d24c1894a0  [33;01mWARN    [00m
> >  [00m              udpsrc
> > gstudpsrc.c:1582:gst_udpsrc_open:<udpsrc0> [00m error: could not add
> > membership: Error joining multicast group: No such device
> > 0:00:00.146782947  [333m 2432 [00m 0x55d24c1894a0  [31;01mERROR   [00m
> >  [00m              udpsrc
> > gstudpsrc.c:1661:gst_udpsrc_close:<udpsrc0> [00m Failed to leave
> > multicast group: Error leaving multicast group: No such device
> > 0:00:00.147097556  [333m 2432 [00m 0x55d24c1894a0  [33;01mWARN    [00m
> >  [00m              udpsrc
> > gstudpsrc.c:1582:gst_udpsrc_open:<udpsrc1> [00m error: could not add
> > membership: Error joining multicast group: No such device
> > 0:00:00.147154020  [333m 2432 [00m 0x55d24c1894a0  [31;01mERROR   [00m
> >  [00m              udpsrc
> > gstudpsrc.c:1661:gst_udpsrc_close:<udpsrc1> [00m Failed to leave
> > multicast group: Error leaving multicast group: No such device
> > 0:00:00.148073188  [333m 2432 [00m 0x55d24c1894a0  [31;01mERROR   [00m
> >  [00m             rtspsrc
> > gstrtspsrc.c:4640:gst_rtspsrc_stream_configure_udp_sinks:<rtspsrc0> [00m
> > failed to create socket
> > 0:00:00.148101780  [333m 2432 [00m 0x55d24c1894a0  [33;01mWARN    [00m
> >  [00m             rtspsrc
> > gstrtspsrc.c:4744:gst_rtspsrc_stream_configure_transport:<rtspsrc0> [00m
> > failed to configure transport
> >
> > I thought that this was because rtspsrc didn't know which interface to
> > use for multicast. So I tried:
> >
> > gst-launch-1.0 rtspsrc multicast-iface=enp0s3 ! ....
> >
> > This doesn't work either, although a different error is reported:
> >
> > [...]
> > Progress: (open) Opened Stream
> > Setting pipeline to PLAYING ...
> > New clock: GstSystemClock
> > Progress: (request) Sending PLAY request
> > Progress: (request) Sending PLAY request
> > 0:00:00.154308014  [335m 3790 [00m 0x7fdd44031a30  [33;01mWARN    [00m
> >  [00m        multiudpsink
> > gstmultiudpsink.c:686:gst_multiudpsink_send_messages:<udpsink0> [00m
> > warning: Error sending UDP packets
> > 0:00:00.154344693  [335m 3790 [00m 0x7fdd44031a30  [33;01mWARN    [00m
> >  [00m        multiudpsink
> > gstmultiudpsink.c:686:gst_multiudpsink_send_messages:<udpsink0> [00m
> > warning: client 239.0.0.1:5000, reason: Error sending message: Network
> > is unreachable
> > WARNING: from element
> > /GstPipeline:pipeline0/GstRTSPSrc:rtspsrc0/GstUDPSink:udpsink0: Error
> > sending UDP packets
> > Additional debug info:
> > ../gst/udp/gstmultiudpsink.c(686): gst_multiudpsink_send_messages ():
> > /GstPipeline:pipeline0/GstRTSPSrc:rtspsrc0/GstUDPSink:udpsink0:
> > client 239.0.0.1:5000, reason: Error sending message: Network is unreachable
> >
> > If I define a default gateway in the machine running GStreamer, then
> > everything works.
> >
> > Is this normal? Why do I need a default gateway to be able to send
> > packets to a multicast address (which is not routed anywhere) ?
> >
> > Best regards,
> >
> > Guillermo Rodriguez Garcia
> > guille.rodriguez at gmail.com
> > _______________________________________________
> > gstreamer-devel mailing list
> > gstreamer-devel at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>
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-- 
Guillermo Rodriguez Garcia
guille.rodriguez at gmail.com