[Live-devel] Possible missing parameter in MPEG4ESVideoRTPSink::auxSDPLine()

[Shaheed Abdol]

Good afternoon,
 
I have hit an interesting obstacle while streaming RTSP video data from
a live source. I am using the openRTSP client to retreive data from a
testOnDemandRTSPServer, which I have added a new
OnDemandServerMediaSubsession type to, named
OnDemandVideoInputSubsession. I am streaming mpeg4 elementaary stream
data (format: 96) and have come across a strange problem. When
ServerMediaSession::generateSDPDescription is called, I trace the call
stack from there down to the
OnDemandServerMediaSubsession::getAuxSDPLine(RTPSink *, FramedSource *)
function, which internally calls MPEG4ESVideoRTPSink::auxSDPLine(). At
the point where the getAuxSDPLine function is called, the RTPSink * and
FramedSource * parameters point to the correct classes. When entering
the MPEG4ESVideoRTPSink::auxSDPLine() function the mp4 video rtpsink
checks a variable named fSource, which should point to the FramedSource
parameter from the preceding call, yet the parameter is not passed in
from the getAuxSDPLine function. Is this a bug, or is there another way
that the fSource parameter gets set? Currently the fSource parameter is
NULL so the function returns prematurely. Without the parameter being
set, my SDP description which gets sent to the client is incomplete and
is missing the line which should read "a=fmtp:96 profile-level-id=3;
...". As a result I can connect to the stream, with any rtsp client
(openRTSP and VLC for instance) but cannot decode the resulting data for
lack of information. I do not want to edit the code in-place, since this
is part of the live555 library, any suggestions to pass the parameters
from OnDemandServerMediaSubsession::getAuxSDPLine(RTPSink *,
FramedSource *) to MPEG4ESVideoRTPSink::auxSDPLine() , or to set the
fSource parameter without destroying the live555 code?
 
Thank you
Regards
___________________________________

Shaheed Abdol
Web: www.scansoft.co.za <http://www.scansoft.co.za/> 
Tel:  +27 21 913 8664
Cell: +27 79 835 8771
 
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