- Guide to using M-Audio Audiophile USB with ALSA and Jack v1.1
+ Guide to using M-Audio Audiophile USB with ALSA and Jack v1.3
========================================================
Thibault Le Meur <Thibault.LeMeur@supelec.fr>
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 caracteristics:
+The internal DAC/ADC has the following characteristics:
* sample depth of 16 or 24 bits
* sample rate from 8kHz to 96kHz
-* Two ports can't use different sample depths at the same time.Moreover, the
+* Two ports 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
+ * 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
Important facts about the Digital interface:
--------------------------------------------
- * The Do port additionnaly supports surround-encoded AC-3 and DTS passthrough,
-though I haven't tested it under linux
+ * The Do port additionally supports surround-encoded AC-3 and DTS passthrough,
+though I haven't tested it under Linux
- Note that in this setup only the Do interface can be enabled
* Apart from recording an audio digital stream, enabling the Di port is a way
-to syncrhonize the device to an external sample clock
+to synchronize the device to an external sample clock
- As a consequence, the Di port must be enable only if an active Digital
source is connected
- Enabling Di when no digital source is connected can result in a
The Audiophile USB MIDI ports will be automatically supported once the
following modules have been loaded:
* snd-usb-audio
- * snd-seq
* snd-seq-midi
-No additionnal setting is required.
+No additional setting is required.
2.2 - Audio ports
-----------------
Audio functions of the Audiophile USB device are handled by the snd-usb-audio
module. This module can work in a default mode (without any device-specific
-parameter), or in an advanced mode with the device-specific parameter called
+parameter), or in an "advanced" mode with the device-specific parameter called
"device_setup".
2.2.1 - Default Alsa driver mode
-The default behaviour of the snd-usb-audio driver is to parse the device
+The default behavior of the snd-usb-audio driver is to parse the device
capabilities at startup and enable all functions inside the device (including
-all ports at any sample rates and any sample depths supported). This approach
+all ports at any supported sample rates and sample depths). This approach
has the advantage to let the driver easily switch from sample rates/depths
automatically according to the need of the application claiming the device.
For people having this problem, the snd-usb-audio module has a new module
parameter called "device_setup".
-2.2.2.1 - Initializing the working mode of the Audiohile USB
+2.2.2.1 - Initializing the working mode of the Audiophile USB
-As far as the Audiohile USB device is concerned, this value let the user
+As far as the Audiophile USB device is concerned, this value let the user
specify:
* the sample depth
* the sample rate
IMPORTANT NOTE WHEN SWITCHING CONFIGURATION:
-------------------------------------------
- * You may need to _first_ intialize the module with the correct device_setup
+ * You may need to _first_ initialize the module with the correct device_setup
parameter and _only_after_ turn on the Audiophile USB device
* This is especially true when switching the sample depth:
- - first trun off the device
- - de-register the snd-usb-audio module
- - change the device_setup parameter (by either manually reprobing the module
- or changing modprobe.conf)
+ - first turn off the device
+ - de-register the snd-usb-audio module (modprobe -r)
+ - change the device_setup parameter by changing the device_setup
+ option in /etc/modprobe.conf
- turn on the device
-2.2.2.3 - Setting and switching configurations with the device_setup parameter
+2.2.2.3 - Audiophile USB's device_setup structure
If you want to understand the device_setup magic numbers for the Audiophile
USB, you need some very basic understanding of binary computation. However,
-this is not required to use the parameter and you may skip thi section.
+this is not required to use the parameter and you may skip this section.
The device_setup is one byte long and its structure is the following:
- choosing b2 will prepare all interfaces for 24bits/96kHz but you'll
only be able to use one at the same time
-2.2.3 - Technical Details for Audiophile Usb
+2.2.3 - USB implementation details for this device
-You may safely skip this section if you're not interrested in driver
+You may safely skip this section if you're not interested in driver
development.
-This section describes some internals aspect of the device and summarize the
-data I got by usb-snooping the windows and linux drivers.
+This section describes some internal aspects of the device and summarize the
+data I got by usb-snooping the windows and Linux drivers.
-The M-Audio Audiophile USB has 7 Usb Interfaces:
+The M-Audio Audiophile USB has 7 USB Interfaces:
a "USB interface":
- * Usb Interface nb.0
- * Usb Interface nb.1
+ * USB Interface nb.0
+ * USB Interface nb.1
- Audio Control function
- * Usb Interface nb.2
+ * USB Interface nb.2
- Analog Output
- * Usb Interface nb.3
+ * USB Interface nb.3
- Digital Output
- * Usb Interface nb.4
+ * USB Interface nb.4
- Analog Input
- * Usb Interface nb.5
+ * USB Interface nb.5
- Digital Input
- * Usb Interface nb.6
+ * USB Interface nb.6
- MIDI interface compliant with the MIDIMAN quirk
Each interface has 5 altsettings (AltSet 1,2,3,4,5) except:
- 16-bit depth, 8-48kHz sample mode
- Synch playback (Do), audio format type III IEC1937_AC-3
-In order to ensure a correct intialization of the device, the driver
+In order to ensure a correct initialization of the device, the driver
_must_know_ how the device will be used:
- * if DTS is choosen, only Interface 2 with AltSet nb.6 must be
+ * if DTS is chosen, only Interface 2 with AltSet nb.6 must be
registered
* if 96KHz only AltSets nb.1 of each interface must be selected
* if samples are using 24bits/48KHz then AltSet 2 must me used if
is not connected
When device_setup is given as a parameter to the snd-usb-audio module, the
-parse_audio_enpoint function uses a quirk called
+parse_audio_endpoints function uses a quirk called
"audiophile_skip_setting_quirk" in order to prevent AltSettings not
corresponding to device_setup from being registered in the driver.
using the "default" ALSA device. This is less efficient than it could be.
Consider using a hardware device instead rather than using the plug layer."
-
3.2 - Patching alsa to use direct pcm device
--------------------------------------------
+--------------------------------------------
A patch for Jack by Andreas Steinmetz adds support for Big Endian devices.
However it has not been included in the CVS tree.
After having applied the patch you can run jackd with the following command
line:
-# /usr/local/bin/jackd -R -dalsa -Phw:1,0 -r48000 -p128 -n2 -D -Chw:1,1
-
+ % jackd -R -dalsa -Phw:1,0 -r48000 -p128 -n2 -D -Chw:1,1
+
+3.2 - Getting 2 input and/or output interfaces in Jack
+------------------------------------------------------
+
+As you can see, starting the Jack server this way will only enable 1 stereo
+input (Di or Ai) and 1 stereo output (Ao or Do).
+
+This is due to the following restrictions:
+* Jack can only open one capture device and one playback device at a time
+* The Audiophile USB is seen as 2 (or three) Alsa devices: hw:1,0, hw:1,1
+ (and optionally hw:1,2)
+If you want to get Ai+Di and/or Ao+Do support with Jack, you would need to
+combine the Alsa devices into one logical "complex" device.
+
+If you want to give it a try, I recommend reading the information from
+this page: http://www.sound-man.co.uk/linuxaudio/ice1712multi.html
+It is related to another device (ice1712) but can be adapted to suit
+the Audiophile USB.
+
+Enabling multiple Audiophile USB interfaces for Jackd will certainly require:
+* patching Jack with the previously mentioned "Big Endian" patch
+* patching Jackd with the MMAP_COMPLEX patch (see the ice1712 page)
+* patching the alsa-lib/src/pcm/pcm_multi.c file (see the ice1712 page)
+* define a multi device (combination of hw:1,0 and hw:1,1) in your .asoundrc
+ file
+* start jackd with this device
+
+I had no success in testing this for now, but this may be due to my OS
+configuration. If you have any success with this kind of setup, please
+drop me an email.