[streaming] Manually creating an SDP-file to input pure RTP

[Alexander Bethke]

Hi everybody,

I'm trying go get streaming running from a mobile device to VLC via RTP, 
no RTCP or RTSP in use. Audio is AAC-LC and sent to port 5002, video is 
MPEG-4 (Part 2) to 5000. To specify codec parameters I use a manually 
created SDP-file. When I use that sdp-file as input (vlc -vvv test.sdp 
--loop), the output shows me the decoder set-up which seems ok to me. 
But after the ports are open (netstat -anu shows them LISTENING), 
nothing happens. No output from VLC/live555, it just times out after 10 
seconds, looping or repeating do not make a difference.
I checked the receival of the RTP packages with Wireshark, positive. 
Also when I just use VLC'S simple RTP input (vlc -vvv rtp://@:port) for 
any of the ports, I get the data, of course terribly misinterpreted, as 
the codecs cannot be recognized.

I've been reading RFC 4566 and tried to make sense of some live555 
source code and as far as I can see, the basic infrastructural 
parameters of the SDP should be ok. The payload-ids for the media 
properties are the ones specified in the client. A problem I'm having is 
that many of the more specific encoding parameters are not known to me 
(crappy Symbian C++ media APIs). Parameters I didn't know where taken 
from a VLC output SDP that I used for 3GP streaming to the device. 
Things that I don't know about the encoding include some basic things 
like audio sampling rate, channels, video frame rate... Also I have no 
idea how the config parameters of the fmtp property are to be gotten right.

Of course that's bad, but how is VLC/live555 supposed to react to wrong 
parameters, does it just throw everything away saying nothing if some of 
the parameters are wrong? Is there anything configured wrongly regarding 
logging? Or is my SDP just so ridiculously wrong? I would need some 
set-up that allowed me some trial-and-error parameter-guessing with dome 
feedback.

I'm running Ubuntu 8.10 with the repository's VLC 0.9.4 packages 
installed, I'm using the unstripped ffmpeg-packages.

Any hints or handles are strongly appreciated,

Alex


++test.sdp
v=0
o=- 14755636972246170349 14755636972246170349 IN IP4 127.0.0.1
s=Unnamed
i=N/A
c=IN IP4 127.0.0.1
t=0 0
a=recvonly
a=type:broadcast
a=charset:UTF-8
m=video 5000 RTP/AVP 96
b=AS:152
a=rtpmap:96 MP4V-ES/90000
a=fmtp:96 profile-level-id=3; 
config=000001b001000001b58913000001000000012000c48d8800cd14042d1463000001b24c61766335312e35302e30;
m=audio 5002 RTP/AVP 97
b=AS:48
a=rtpmap:97 MP4A-LATM/44100/2
a=fmtp:97 profile-level-id=15; object=2; cpresent=0; config=400024203fc0
++