A:

The Miles MP3 decoder is amazingly fast - we have Intel x87, Intel SSE, AMD 3DNow, PowerPC and MIPS assembly optimized versions. On a modern PC, you can play 32 44 Khz stereo MP3 files using about 12% of the CPU. On a Mac, 32 samples use about 25%. On an Xbox 360, 32 samples use 19%. On a slower platform like PS/2, one MP3 sample takes about 8% of the CPU.

You can cut the CPU hit almost linearly by dropping the sample rate, and/or the number of channels. For example, 44 Khz mono takes as little as 1.5%.

In general, we've seen very few places where the CPU hit of MP3 is a problem. Remember that if you are streaming audio in off a drive, you usually take a larger CPU hit just in I/O overhead (which MP3 will help because you are reading a tenth as much data).