[diamond-optic]

I've never used it myself so I dont know how it works, but the people I know that rip live streams (or replays) use RTMPDump to get an exact copy of the stream. And the end results they get are 1000x better then those crappy screen captures and stuff that a lot of people do.

I would assume google can probably find you some guides to getting it working. And since Yahoo Live is a well known site, theres a good chance that somewhere there is a guide that has the info you need specifically for that site