[Live-devel] RTP packet rate smoothing?

[Clem Taylor]

Hi,

We have been doing some experiments trying to push MPEG4 video via
rtsp over a 900mhz wireless data link. The radio module only has a 10
packet buffer, so larger IVOPs will overrun the input packet buffer
before the packets can be sent. Our MPEG4 encoder likes to emit fairly
large IVOPs (especially for mostly static scenes). I can reduce the
VBV buffer size to minimize the worst case frame size, but this really
kills the image quality.

Currently, all the RTP packets that make up a video frame are sent out
back to back. I'd like to spread out the delivery of the RTP packets
over the entire frame time instead of blasting them out all at once.

One possible solution for this is to use the kernel traffic shaper to
smooth out the data rate. We plan on using the packet classifier to
give higher priority to video packets, but I'm not sure that shaping
the video data is a good thing. I want to smooth out the transmission
of the RTP packets that don't marker bit set, but not delay the
packets that complete a VOP.

An earlier list post on a similar topic mentions modifying
fNextSendTime to delay the next packet, however it seems that this
timer effects the time between frames, not the time between packets
that make up a frame.

Any suggestions on to spread out the packets that make up a given
frame so they are uniformly distributed over the frame time
(durationInMicroSeconds).

                                   Thanks,
                                   Clem Taylor