Media Server :: Dynamic Streaming While In The Process Of Writing A Tutorial Not Working

I've been experimenting with Dynamic Streaming while in the process of writing a tutorial. The documentation is quite clear on a few points: The keyframe interval in the various encodings should be shortThe bufferlength should be at least 2x the keyframe intervalThe player should sense a bandwidth change, by default, within the 4-second sampling interval and call for a switch. Then, the switch could take as long as 2x the keyframe interval after that. What I'm finding is wildly different behavior than this. It takes anywhere from 10-15 seconds for the player to notice the change and call for a switch, then another 20-40 seconds for the switch to happen. When switching up to a higher bitrate stream, this just means the user gets low bitrate video for longer than they ought to. But when switching down due to falling bandwidth, the buffer runs out and the user stares at the rebuffering sign for a lengthy time - long enough to give up on watching the video, for sure.

I've encoded an H.264 MP4 file at 64, 384, and 768 kbps, at 30fps and an "every 60 frames" keyframe interval. I've streamed it rtmp via two different CDNs that use FMS 3.5, into two different Flash video players (JW Player and Flowplayer). I've restricted my bandwidth on Windows XP with Netlimiter 2.0; and on the Mac with 'ipfw'. I've set bufferlength between 4 and 10 seconds. I've tested switching up and switching down. For up, I start with a 200kbps bandwidth limit. The video starts OK with the correct stream, then at 5 seconds I open up the bandwidth to unrestricted. For testing down, I do the opposite: start at unrestricted and then at 00:05 restrict to 200kbps.

My test page, with both players and sample code is at [URL] n-flash-bitrate-switching/ I also have a couple of screen recordings there showing the behavior of the whole process, both switching up and switching down. I thought I've done everything right here - paid attention to every documented detail, but it works rather poorly. Can someone explain whether this is expected behavior, if the players have implemented dynamic switching poorly, or if I'm doing something wrong?