[Live-devel] RockwellCollins playback problem and controlling bit rates

[mamille1 at rockwellcollins.com]

All

Thanks for the earlier advice. We think that our earlier problem with 
large frames in a recorded video stream was due to insufficient socket 
buffer space on the receiving end during a recording. ("Large frames" were 
2x-5x the size of a normal I-frame or P-frame, but only a fraction of that 
was really picture data.) 

Now that we have improved recordings of our video stream, we are working 
to make playback of those stream files from our storage media look better. 
A lot of our playback problem stems from sending data to our DSP decoder 
slightly faster than it can handle. This leads to stutters in the playback 
(dropped frames) and a sort of digital splatter (blocky video until the 
next I-frame). We have tried a couple of ways to reduce the rate at which 
we send data to the decoder, including slowing our system clock down a 
bit. (Our CPU has no real time clock, and our DSP is not clocked at the 
same rate as the CPU.)

We are looking at controlling the bit rate used during a recording and 
playback rather than adjusting system time. In our system, we can set a 
target bit rate used by the DSP when encoding analog to digital, but that 
seems to work by dropping frames. This makes our recordings look a little 
worse than before when played back on a PC, since we're missing some 
frames. 

Is there a mechanism in the live555 library that allows us to control the 
bit rate in a playback from our CPU to our DSP  without dropping entire 
video frames? 

Thanks!

-=- Mike Miller
Rockwell Collins, Inc.
Cedar Rapids, IA 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.live555.com/pipermail/live-devel/attachments/20080814/db03cc3d/attachment.html>