[Live-devel] Streaming H264 difficulties

[Yaron Levy]

Hi,
I am working on a RTSP RTP-over-TCP H264 streaming application from a live
HW-based encoder.
I have implemented MyDeviceSource, MyH264VideoStreamFramer,
H264DeviceMediaSubsession and MyH264App based on testOnDemandRTSPServer. In
general the application works and I get the live stream.
The intended viewer application is VLC on a remote machine in the same LAN,
where bandwidth is a non-issue.
 
I've encountered 2 obstacles that have been giving me a hard time:
1. "Glitches" in the video output. After every (quite small) amount of
frames the video "glitches" and I get block artifacts, and frames that seem
to jump back in time. From playing around with the presentation times, I
thought it might be related to this. 
My approach to fPresentationTime is to set it to gettimeofday() every GOP
(i.e. SPS/PPS frames), and increment by 1000000/FPS for every encoded frame.
The encoder encodes frame by frame only.
When I use openRTSP as the client, the video file is saved perfectly, which
no glitches. 
 
2. The streaming server (OS is Linux2.6) is also used for other
cpu-intensive processes. This is a requirement. The machine is practically
constantly at 100% cpu usage. However, it practically does not use any
network resources.
When this is the situation, the video glitches become overwhelming, and it
seems the client has a very hard time handling the stream and sometimes even
disconnects.
So the question is how and where is Live555 subject to cpu load, and why
does it have such a catastrophic effect on the video output given that
network usage is low. 
Could this be related also to (1)?
 
Thanks,
Yaron Levy
Emza Visual Sense Ltd.
Research & Development
Email:  <mailto:yaron at emza-vs.com> yaron at emza-vs.com
Tel: (972)-52-2968679
 
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