[Mp4-tech] VOP Start Codes and MPEG-4 over RTP

[Phillip Bruce]

hello and good day,
I think you've got your marker information all wrong.  RFC 3016 calls for
setting the marker bit in the last packet of a VOP.  Here's what we 
get from a visual stream broadcast by MPEG4IP:
datagram from=192.168.0.200:41700 to=192.168.0.13:23984
1075891295.083499 RTP len=1472 v=2 p=0 x=0 cc=0 m=0 pt=96 (????,0,0) 
seq=32657 ts=118282040 ssrc=0x121131d3 data=000001b6
datagram from=192.168.0.200:41700 to=192.168.0.13:23984
1075891295.083649 RTP len=1472 v=2 p=0 x=0 cc=0 m=0 pt=96 (????,0,0) 
seq=32658 ts=118282040 ssrc=0x121131d3 data=cbd5b510
datagram from=192.168.0.200:41700 to=192.168.0.13:23984
1075891295.083685 RTP len=492 v=2 p=0 x=0 cc=0 m=1 pt=96 (????,0,0) 
seq=32659 ts=118282040 ssrc=0x121131d3 data=3d4d8776
datagram from=192.168.0.200:41700 to=192.168.0.13:23984
1075891295.163390 RTP len=338 v=2 p=0 x=0 cc=0 m=1 pt=96 (????,0,0) 
seq=32660 ts=118289540 ssrc=0x121131d3 data=000001b6
Here, seq #32657-32659 correspond to a single VOP (m=0, m=0, m=1), #32660
also (m=1).  The first 4 octets of the payload data in these sample
pakcets also conform to the standard.  You apparently are also forgetting
that a single RTP packet MAY contain several VOPs.
sincerely,
dI77IHd
On Tue, 3 Feb 2004, Stefan A. Goor wrote:
> Hey All,
> I'm hoping the answer to this question is going to be very simple.
> I am working with MPEG-4 and RTSP so that the content is sent over RTP but
> the client I am developing needs to know when the start new VOP is received.