[gstreamer-bugs] [Bug 634419] New: Selecting a subset of streams available in rtspsrc

GStreamer (bugzilla.gnome.org) bugzilla at gnome.org
Tue Nov 9 06:14:11 PST 2010


https://bugzilla.gnome.org/show_bug.cgi?id=634419
  GStreamer | gst-plugins-good | 0.10.x

           Summary: Selecting a subset of streams available in rtspsrc
    Classification: Desktop
           Product: GStreamer
           Version: 0.10.x
        OS/Version: All
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: Normal
         Component: gst-plugins-good
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: GStreamer-Bugs at tycosp.com
         QAContact: gstreamer-bugs at lists.sourceforge.net
      GNOME target: ---
     GNOME version: ---


We are currently developing a GStreamer-based video/audio streaming application
that can receive RTSP/RTP streams from security cameras.  We currently need to
enhance the rtspsrc element and want to solicit feedback from the GStreamer
developer community.

Some cameras we need to receive streams from have both audio and video streams
available and will describe both a video and an audio stream in their response
to a DESCRIBE request.  The GStreamer rtspsrc element will send a SETUP request
for each of the media streams listed in the SDP of the DESCRIBE response and
the camera will transmit both streams to our application when using the rtspsrc
element.  In certain circumstances, we would like to change the behavior of
rtspsrc in our application.  Sometimes, when a camera (herein referred to as a
“device”) indicates that it has multiple streams available in its DESCRIBE
response, we would like to send a SETUP request for only one of the streams.  

Stated more generally, if a DESCRIBE response indicates that it has M number of
media streams available, we might want to send SETUP requests for some subset
of the available streams less than M.   This would tell the device to only
transmit those streams we’re interested in when we send a PLAY request.  To
accomplish this, we were thinking of changing rtspsrc so that RTP ghost pads
would be created for each stream that the device enumerates in its DESCRIBE
response.  However, we would only send a SETUP request (and hook up all the
internal rtspsrc bin plumbing) when the appropriate ghost pad is linked to
another element’s sink pad.  This way, the device would only play those streams
we’re interested in when we send the RTSP PLAY request.   This change is
obviously a significant departure from how rtspsrc currently operates where all
streams listed in the DESCRIBE response’s SDP are set up by rtspsrc in the
state transition from READY to PAUSED.  As such, we wanted to pick your brain
briefly before moving too far on this change.

A few questions:

1. Is this enhancement something that would merit inclusion in the GStreamer
project?  
2. If so, would it make sense for it to be a completely different rtspsrc-like
element (maybe something like “rtspsrc-selective”)?  Or would it be preferable
to have both “modes” reside in a single rtspsrc element and we would change the
operating mode of rtspsrc based on an element property?
3. Are there any issues that jump out as being something to watch for as we
think about implementing this scheme?

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