Documentation/sound/cards/audiophile-usb.rst

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========================================================
Guide to using M-Audio Audiophile USB with ALSA and Jack
========================================================

v1.5

Thibault Le Meur <Thibault.LeMeur@supelec.fr>

This document is a guide to using the M-Audio Audiophile USB (tm) device with 
ALSA and JACK.

History
=======

* v1.4 - Thibault Le Meur (2007-07-11)

  - Added Low Endianness nature of 16bits-modes
    found by Hakan Lennestal <Hakan.Lennestal@brfsodrahamn.se>
  - Modifying document structure

* v1.5 - Thibault Le Meur (2007-07-12)
  - Added AC3/DTS passthru info


Audiophile USB Specs and correct usage
======================================

This part is a reminder of important facts about the functions and limitations 
of the device.

The device has 4 audio interfaces, and 2 MIDI ports:

 * Analog Stereo Input (Ai)

   - This port supports 2 pairs of line-level audio inputs (1/4" TS and RCA) 
   - When the 1/4" TS (jack) connectors are connected, the RCA connectors
     are disabled

 * Analog Stereo Output (Ao)
 * Digital Stereo Input (Di)
 * Digital Stereo Output (Do)
 * Midi In (Mi)
 * Midi Out (Mo)

The internal DAC/ADC has the following characteristics:

* sample depth of 16 or 24 bits
* sample rate from 8kHz to 96kHz
* Two interfaces can't use different sample depths at the same time.

Moreover, the Audiophile USB documentation gives the following Warning:
  Please exit any audio application running before switching between bit depths

Due to the USB 1.1 bandwidth limitation, a limited number of interfaces can be 
activated at the same time depending on the audio mode selected:

 * 16-bit/48kHz ==> 4 channels in + 4 channels out

   - Ai+Ao+Di+Do

 * 24-bit/48kHz ==> 4 channels in + 2 channels out, 
   or 2 channels in + 4 channels out

   - Ai+Ao+Do or Ai+Di+Ao or Ai+Di+Do or Di+Ao+Do

 * 24-bit/96kHz ==> 2 channels in _or_ 2 channels out (half duplex only)

   - Ai or Ao or Di or Do

Important facts about the Digital interface:

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