Most of the recent Macintosh computers come with sound input hardware. There are probably exceptions to this, but the older and some of the current low-end machines have 8 bit (linear) mono hardware running at 22254.54 samples/second. All of the PowerPC, AV, and the 500 series notebook computers come with 16 bit 44kHz stereo sampling hardware. They can also record at 22050 samples/second. The sound manager implements an AGC (Automatic Gain Control) function for the 8 bit hardware. The drivers have a switch to turn off the AGC.
There are a number of DSP vendors that support high quality audio. Generally this means quieter analog sections, and more IO formats (AES/IBU, for example). Try DigiDesign and Spectral Innovations.
The software drivers for sound are described in "Inside Macintosh: Sound". If you want to see some sample code check out the sources for the Matlab "Sound and Image Toolbox". They can be found at
Routines that play and record sounds using the toolbox are included (and interfaced to Matlab).
Section 2 of the
comp.speech FAQ Home Page.
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