Audio Devices: Hardware Rate Converter Audio MIDI Setup -> Audio Devices -> Built-in Input has four configurable audio parameters:


Sample Rate
Sample Size
Channel Volume
Hardware Rate Converter


The Hardware Rate Converter has three options:


Automatic
Enable
Disable


This "Hardware Rate Converter" has basically no google presence. Having a decent understanding of digital audio I can infer what these three options will do, but I don't feel confident knowing what the specific correlation is between these options and the actual bits being processed by my mac on input.

So. Where can I find general specs on this thing? I'll settle for just knowing what (if any) latency these three options incur.



Macbook Pro 10.7.3 (11D50)

15-inch, 2.53GHz, Mid 2009

2.53 GHz Intel Core 2 Duo 

Memory 4 GB 1067 MHz DDR3

Intel High Definition Audio, Audio ID: 76
Apple has documentation for this in Mountain Lion.


  If your computer contains support for the hardware sample rate converter, the Hardware Rate Converter pop-up menu is available in the Input menu. When you choose Automatic from the pop-up menu, the hardware sample rate converter is turned on if the audio samples coming in are PCM and formatted according to the international standard IEC 60958-3. The hardware sample rate converter is turned off if the input stream is encoded. You can also choose Enable or Disable from the menu to keep the hardware sample rate converter turned on or off.


So this would only be useful if you have something like a S/PDIF input and wanted the audio converted to a different digital rate.  I don't have any specs on it, but I would expect the hardware rate converter to have very low latency compared to software rate conversion.