[YouTube-API] how to determine/detect whether youtube video buffering finishes

I used tcpdump to capture youtube pakcets
if I start to play a video, I want to determine/detect when youtube video buffering/streaming finishes
is there a special packet that  is related  to the end of video buffering/streaming?

or can I use other method, like javascript to log the time when youtube video buffering/streaming finishes
thanks!

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Starting October 15, 2012, this group will stop accepting new posts. We recommend that developers start using Stack Overflow and the Issue Tracker for YouTube API support. More details about this change and relevant links can be found at http://apiblog.youtube.com/2012/09/the-youtube-api-on-stack-overflow.html