Ask an FMS Guru #33: I'm having trouble viewing streamed video, it starts and stops a lot, what's wrong here?

This most definitely doesn't pertain just to Flash Media Server, but it's a good question that I think quite a few people ask themselves when working with FMS2.

The question: I'm having trouble viewing streamed video, it starts and stops a lot, what's wrong here?

The answer:

To start off, let's talk about video file encoding. Video files can be encoded in two different ways, CBR (constant bit rate) and VBR (variable bit rate). If you were to encode a file with CBR at 600 kbps then throughout the whole video it would be 600 kbps, even if there wasn't really a need to have that much information.

Whereas, if you were to encode in VBR at 600kbps, the encoder would change the bit rate based on whether or not there is a lot of information changing around etc.

So on that note for FMS, and progressive streaming for that matter, it becomes a bit more difficult for the player to properly buffer VBR because the bit rate is always changing. For CBR it becomes rather simple because it's easy math. Meaning, one question you need to ask yourself is whether it is more beneficial to encode in VBR or CBR.

This all goes down the toilet of course if you have a bad network connection that drops or just gets really bad at times and then good at times. Buffering is a bit of a science and I've got just the article for you to look at if you want to learn more about that and how to more smartly buffer video. Thanks to a super video genius, Fabio Sonnati, we all now have this article to refer to when we want to learn how to buffer video in a more intelligent way than just setting the buffer via the netStream object.

So essentially, if your video is stuttering or stopping and starting a whole bunch of time then most likely you aren't buffering properly. See the article above on how to deal with that in a better way than you are now.

Posted by Graeme at October 18, 2007 04:01 AM