In 48 kHz Audio Can Cause Loss of Synch with Flash Playback, Jan Ozer notes previous observations that “Flash Player resamples all sound sources to 44.1 kHz during playback.” This is the apparent culprit for loss of audio sync in some live playback, and there might be distortion introduced as well.
For some of us, this means resampling not just for F4V but for H.264 encoding too (pictured: Adobe Flash Live Media Encoder).
See also occasional free extracts from Ozer’s Producing Great Video with the Adobe Media Encoder at Video2brain.