[vlc] Re: H263 over RTP

[chris.2.dobbs at bt.com]

I was told by one of the helpful chaps here that the one to go for is
RFC4629 - but I believe VLC does support the other ones. Basically the
h263 header changes from 4 bytes to 2 bytes for RFC4629.
I can get VLC to play RFC4629 fine now. If you want reference code ,
look at the live55 code base as there is a ready to go H263 RTP streamer
there. (and an RTSP one too).
-Chris

________________________________

From: vlc-bounce at videolan.org [mailto:vlc-bounce at videolan.org] On Behalf
Of jogging song
Sent: 07 March 2007 14:26
To: vlc at videolan.org
Subject: [vlc] Re: H263 over RTP


Hi, Chris
     There are three RFCs about h.263 packet, that is RFC 2190, RFC2429
and RFC4629. Doe vlc support all these three RFCs?

thanks in advance.
Jogging


On 3/6/07, chris.2.dobbs at bt.com <chris.2.dobbs at bt.com> wrote: 

	All, 
	If anyone is interested I have managed to get VLC to playback
file based H263 video remotely over RTP (as a non-encapsulated
elementary stream).

	I had trouble getting this to work as I couldn't figure out how
to transpose the file based H263 records into RFC4629 RTP packets. I
finally managed to reverse engineer to live555 code (which includes an
H263 streamer module) and this is what u have to do: 

	Many thanks to Ross Finlayson BTW who prodded me in the right
direction several times... 

	The following does not detail all the RTP field setups as they
are not crucial to getting this to work, things like sequence number and
time stamps are taken as read...

	1. Read 5 bytes first (from file based H263 data) , this gives
you a starting frame of reference. 
	    Create 1st RTP packet and set the M bit to 1 
	    Create and add to RTP payload the 2 byte H263 header and set
the P bit to 1 (zero rest out) 
	   
	    copy the 5 byte record  into the RTP payload body (after the
H263 header). 
	  
	    Send it 

	2. Read as much as u can from file without blowing your MTU , in
my case this is 1500 so I chose 1436 (like the live555 code)

	    Create new RTP packet + new 2 byte H263 header 
	    Scan newly read in H263 record for occurance of end of frame
marker - this is two consectutive bytes of zeros (00 00).

	        
	    pseudo code follows: 

	     IF eof frame marker found: 
	               This record contains an end of frame so set the
RTP M bit to 1 and  set the H263 header P bit to 0, then copy to RTP
payload (after H263 header) 

	            the record data  up to but NOT including the "0000".
Store remainder in temp. 
	            The next record read will therefore be a new start
of frame. 

	    IF eof frame marker not found: 
	               IF previous record read contained an end of frame
marker 
	                           prefix the this packet with any
remainder stored in temp and set the P bit to 1 
	                           and the M bit to 0.          
	                           Need to make sure at this point that
we don't blow the MTU. 
	               ELSE 
	                           Set RTP M bit to 0 and H263 P bit to
0 and copy whole record into RTP payload(after the H263 header).

	    Send it ! 

	3. Repeat 2 until EOF 


	To get a remote vlc to read this stream, create an sdp file like
this 

	 v=0 
	o=- 7776 3 IN IP4 10.215.130.112 
	s=Test H263 stream 
	i=Parameters for the session streamed by "ChipsAhoyH263" 
	t=0 0 
	m=video 7776 RTP/AVP 98 
	a=rtpmap:98 H263-1998/90000 
	a=fmtp:98 profile=0; level=40 
	b=TIAS:2048000 


	Where 7776 is the port you are streaming out to from above
steps. 
	Save as say c:\testH263.sdp 

	Start vlc like this: 

	Vlc -vvv file://c:\testH263.sdp 


	Start the stream and u should see video. 

	I guess I should have figured all this out from the various
RFC's but to actually implement was not exactly straightforward - no
where could I find info on how to look for the end of frame marker
("0000") which is the key to the whole thing! 

	Hope this helps as it drove me nuts... 
	-Chris 


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