Saved live stream problem

I have a client that broadcast video and audio, then on the server, it would save the stream into a flv file.
When i playback the video, it's very jerky.
I'm using Red5 hudson build #156. It was fine before the patch from absolute to relative timestamp.

More information, on the server code, I call

ClientBroadcastStream stream = ...;
stream.saveAs(steamNAme,false);

to start recording the live stream. Then i call

ClientBroadcastStream stream = ...;
stream.stopRecording();

to stop recording the live stream.

I tried creating a simple video playback application in openlaszlo and adobe flex, both will play the video jerkyly. Seems like the video pause and play very frequently.