Has anyone succeeded in modifying the LiveMedia classes to support
accepting parameters in the URI, something like the following to
request a specific height and width, bitrate, and framerate:
rtsp://media.server.com/live_video?height=320&width=400&kbps=300&fps=15
With a H.264 stream changing some of these parameters will change
the SPS, and PPS and thus change the SDP. The way RTSPServer,
ServerMediaSession, and OnDemandMediaSession work they all make
assumptions about the media name and that the SDP will not change
For this reason, you should probably treat each stream as having its
own "ServerMediaSubsession" (subclass) object, rather than trying to
use the same "ServerMediaSubsession" (subclass) object for each
stream. That way, these objects can continue to work from the
assumption that their SDP config information - once set up - will not
change.
For example (to use your example string),
"live_video?height=320&width=400&kbps=300&fps=15" would use a
completely separate "ServerMediaSubsession" (subclass) object than
"live_video?height=320&width=400&kbps=300&fps=30".
You can probably do this by subclassing "RTSPServer" and redefining
the virtual function "lookupServerMediaSession()" in your subclass.
Plus, of course, you'll need your own subclass of
"OnDemandServerMediaSubsession" (it'll be similar to
"H264VideoFileServerMediaSubsession" if you're streaming H.264), but
you're presumably already doing that.
Once again, when you think of extending the supplied code, you should
be thinking first about subclassing, and modify the supplied code
only as a last resort (if at all).
I also want to remind everyone that subclassing the code considerably
simplifies your obligations under the LGPL. If you modify the
supplied code, and then release a product based on these
modifications, then you are required to also make your modified
source code available. If, instead, you subclass the supplied code
(without modifying it), then you are not required to make available
any of your source code.
--
Ross Finlayson
Live Networks, Inc.
http://www.live555.com/
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