Invisible wrote:
> I know that MPEG has several different kinds of frames, some of which 
> are individual, independent frames, and some of which are related to 
> previous frames. I can just never remember the exact details; every 
> reference on the subject that I've ever read has made it sound insanely 
> complex, when obviously it isn't.

It's pretty easy. There's three kinds of frames:

I - Independent. Basically JPEG. Used when going FF and Fast Reverse. 
About every half second.

P - Predictive. Differences based on the previous I frame. About five 
per I frame.

B - Bidirectional. Based in the previous and following frame.

Lots of cheaper mpeg encoding software doesn't do B frames, because 
they're a PITA to calculate efficiently. Natch, with faster and faster 
CPUs, this becomes less of a problem. 5 or 10 years ago, you could spend 
weeks looking for an easy-to-use compressor that would do B frames.

I think the higher numbered MPEGs added more options to the encoding of 
B frames, so that you could look at more than just one frame away, for 
example.

> Damn. And here I was thinking an integer-arithmetic FFT would be really 
> fast...

When your CPU is a 16-bit CPU on an 8-bit bus running at a dozen MHz, 
even integer FFT is slow.

-- 
Darren New / San Diego, CA, USA (PST)

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