[Live-devel] Drift over time

[Ralf Globisch]

Hi,
I've written a basic RTSP server using live555 which streams live audio (PCM) and video (H263) to Windows Media Player.

On the server side I've created a custom source similar to DeviceSource in which I set the presentation time of each sample using gettimeofday and since it's a live source I'm using 0 for fDurationInMicroSeconds.

I've added RTCP instances for both audio and video and everything seems to be synchronised properly on the client side.
However after streaming for a couple of hours the audio and video seem to drift apart by a couple of seconds (approx 12 seconds of drift after more than 12 hours of streaming). This is the case where I'm running both server and client on the same machine- hence my sender and receiver clocks are definitely synchronised.

Has anyone else experienced this?

I'm guessing this might be some sort of compounded rounding error/ numerical inaccuracy since it only occurs after a couple of hours?

I've tried linking the fPresentationTime to the DirectShow start time stamp of each incoming media sample instead of using gettimeofday, but also experienced drift.

Any suggestions will be greatly appreciated,

Thanks,
Ralf


-- 
This message is subject to the CSIR's copyright terms and conditions, e-mail legal notice, and implemented Open Document Format (ODF) standard. 
The full disclaimer details can be found at http://www.csir.co.za/disclaimer.html.

This message has been scanned for viruses and dangerous content by MailScanner, 
and is believed to be clean.  MailScanner thanks Transtec Computers for their support.