1 Guide to using M-Audio Audiophile USB with ALSA and Jack v1.1
2 ========================================================
4 Thibault Le Meur <Thibault.LeMeur@supelec.fr>
6 This document is a guide to using the M-Audio Audiophile USB (tm) device with
9 1 - Audiophile USB Specs and correct usage
10 ==========================================
11 This part is a reminder of important facts about the functions and limitations
14 The device has 4 audio interfaces, and 2 MIDI ports:
15 * Analog Stereo Input (Ai)
16 * Analog Stereo Output (Ao)
17 * Digital Stereo Input (Di)
18 * Digital Stereo Output (Do)
22 The internal DAC/ADC has the following caracteristics:
23 * sample depth of 16 or 24 bits
24 * sample rate from 8kHz to 96kHz
25 * Two ports can't use different sample depths at the same time.Moreover, the
26 Audiophile USB documentation gives the following Warning: "Please exit any
27 audio application running before switching between bit depths"
29 Due to the USB 1.1 bandwidth limitation, a limited number of interfaces can be
30 activated at the same time depending on the audio mode selected:
31 * 16-bit/48kHz ==> 4 channels in/ 4 channels out
33 * 24-bit/48kHz ==> 4 channels in/2 channels out,
34 or 2 channels in/4 channels out
35 - Ai+Ao+Do or Ai+Di+Ao or Ai+Di+Do or Di+Ao+Do
36 * 24-bit/96kHz ==> 2 channels in, or 2 channels out (half duplex only)
37 - Ai or Ao or Di or Do
39 Important facts about the Digital interface:
40 --------------------------------------------
41 * The Do port additionnaly supports surround-encoded AC-3 and DTS passthrough,
42 though I haven't tested it under linux
43 - Note that in this setup only the Do interface can be enabled
44 * Apart from recording an audio digital stream, enabling the Di port is a way
45 to syncrhonize the device to an external sample clock
46 - As a consequence, the Di port must be enable only if an active Digital
48 - Enabling Di when no digital source is connected can result in a
49 synchronization error (for instance sound played at an odd sample rate)
52 2 - Audiophile USB support in ALSA
53 ==================================
57 The Audiophile USB MIDI ports will be automatically supported once the
58 following modules have been loaded:
63 No additionnal setting is required.
68 Audio functions of the Audiophile USB device are handled by the snd-usb-audio
69 module. This module can work in a default mode (without any device-specific
70 parameter), or in an advanced mode with the device-specific parameter called
73 2.2.1 - Default Alsa driver mode
75 The default behaviour of the snd-usb-audio driver is to parse the device
76 capabilities at startup and enable all functions inside the device (including
77 all ports at any sample rates and any sample depths supported). This approach
78 has the advantage to let the driver easily switch from sample rates/depths
79 automatically according to the need of the application claiming the device.
81 In this case the Audiophile ports are mapped to alsa pcm devices in the
82 following way (I suppose the device's index is 1):
83 * hw:1,0 is Ao in playback and Di in capture
84 * hw:1,1 is Do in playback and Ai in capture
85 * hw:1,2 is Do in AC3/DTS passthrough mode
87 You must note as well that the device uses Big Endian byte encoding so that
88 supported audio format are S16_BE for 16-bit depth modes and S24_3BE for
89 24-bits depth mode. One exception is the hw:1,2 port which is Little Endian
90 compliant and thus uses S16_LE.
93 * playing a S24_3BE encoded raw file to the Ao port
94 % aplay -D hw:1,0 -c2 -t raw -r48000 -fS24_3BE test.raw
95 * recording a S24_3BE encoded raw file from the Ai port
96 % arecord -D hw:1,1 -c2 -t raw -r48000 -fS24_3BE test.raw
97 * playing a S16_BE encoded raw file to the Do port
98 % aplay -D hw:1,1 -c2 -t raw -r48000 -fS16_BE test.raw
100 If you're happy with the default Alsa driver setup and don't experience any
101 issue with this mode, then you can skip the following chapter.
103 2.2.2 - Advanced module setup
105 Due to the hardware constraints described above, the device initialization made
106 by the Alsa driver in default mode may result in a corrupted state of the
107 device. For instance, a particularly annoying issue is that the sound captured
108 from the Ai port sounds distorted (as if boosted with an excessive high volume
111 For people having this problem, the snd-usb-audio module has a new module
112 parameter called "device_setup".
114 2.2.2.1 - Initializing the working mode of the Audiohile USB
116 As far as the Audiohile USB device is concerned, this value let the user
120 * whether the Di port is used or not
122 Here is a list of supported device_setup values for this device:
123 * device_setup=0x00 (or omitted)
124 - Alsa driver default mode
125 - maintains backward compatibility with setups that do not use this
126 parameter by not introducing any change
127 - results sometimes in corrupted sound as decribed earlier
129 - 16bits 48kHz mode with Di disabled
130 - Ai,Ao,Do can be used at the same time
131 - hw:1,0 is not available in capture mode
132 - hw:1,2 is not available
134 - 16bits 48kHz mode with Di enabled
135 - Ai,Ao,Di,Do can be used at the same time
136 - hw:1,0 is available in capture mode
137 - hw:1,2 is not available
139 - 24bits 48kHz mode with Di disabled
140 - Ai,Ao,Do can be used at the same time
141 - hw:1,0 is not available in capture mode
142 - hw:1,2 is not available
144 - 24bits 48kHz mode with Di enabled
145 - 3 ports from {Ai,Ao,Di,Do} can be used at the same time
146 - hw:1,0 is available in capture mode and an active digital source must be
148 - hw:1,2 is not available
149 * device_setup=0x0D or 0x10
151 - Di is enabled by default for this mode but does not need to be connected
153 - Only 1 port from {Ai,Ao,Di,Do} can be used at the same time
154 - hw:1,0 is available in captured mode
155 - hw:1,2 is not available
157 - 16bits 48kHz mode with only the Do port enabled
158 - AC3 with DTS passthru (not tested)
159 - Caution with this setup the Do port is mapped to the pcm device hw:1,0
161 2.2.2.2 - Setting and switching configurations with the device_setup parameter
163 The parameter can be given:
164 * By manually probing the device (as root):
165 # modprobe -r snd-usb-audio
166 # modprobe snd-usb-audio index=1 device_setup=0x09
167 * Or while configuring the modules options in your modules configuration file
168 - For Fedora distributions, edit the /etc/modprobe.conf file:
169 alias snd-card-1 snd-usb-audio
170 options snd-usb-audio index=1 device_setup=0x09
172 IMPORTANT NOTE WHEN SWITCHING CONFIGURATION:
173 -------------------------------------------
174 * You may need to _first_ intialize the module with the correct device_setup
175 parameter and _only_after_ turn on the Audiophile USB device
176 * This is especially true when switching the sample depth:
177 - first trun off the device
178 - de-register the snd-usb-audio module
179 - change the device_setup parameter (by either manually reprobing the module
180 or changing modprobe.conf)
183 2.2.2.3 - Setting and switching configurations with the device_setup parameter
185 If you want to understand the device_setup magic numbers for the Audiophile
186 USB, you need some very basic understanding of binary computation. However,
187 this is not required to use the parameter and you may skip thi section.
189 The device_setup is one byte long and its structure is the following:
191 +---+---+---+---+---+---+---+---+
192 | b7| b6| b5| b4| b3| b2| b1| b0|
193 +---+---+---+---+---+---+---+---+
194 | 0 | 0 | 0 | Di|24B|96K|DTS|SET|
195 +---+---+---+---+---+---+---+---+
198 * b0 is the "SET" bit
199 - it MUST be set if device_setup is initialized
200 * b1 is the "DTS" bit
201 - it is set only for Digital output with DTS/AC3
202 - this setup is not tested
203 * b2 is the Rate selection flag
204 - When set to "1" the rate range is 48.1-96kHz
205 - Otherwise the sample rate range is 8-48kHz
206 * b3 is the bit depth selection flag
207 - When set to "1" samples are 24bits long
208 - Otherwise they are 16bits long
209 - Note that b2 implies b3 as the 96kHz mode is only supported for 24 bits
211 * b4 is the Digital input flag
212 - When set to "1" the device assumes that an active digital source is
214 - You shouldn't enable Di if no source is seen on the port (this leads to
215 synchronization issues)
216 - b4 is implied by b2 (since only one port is enabled at a time no synch
218 * b5 to b7 are reserved for future uses, and must be set to "0"
219 - might become Ao, Do, Ai, for b7, b6, b4 respectively
222 * there is no check on the value you will give to device_setup
223 - for instance choosing 0x05 (16bits 96kHz) will fail back to 0x09 since
224 b2 implies b3. But _there_will_be_no_warning_ in /var/log/messages
225 * Hardware constraints due to the USB bus limitation aren't checked
226 - choosing b2 will prepare all interfaces for 24bits/96kHz but you'll
227 only be able to use one at the same time
229 2.2.3 - Technical Details for Audiophile Usb
231 You may safely skip this section if you're not interrested in driver
234 This section describes some internals aspect of the device and summarize the
235 data I got by usb-snooping the windows and linux drivers.
237 The M-Audio Audiophile USB has 7 Usb Interfaces:
241 - Audio Control function
251 - MIDI interface compliant with the MIDIMAN quirk
253 Each interface has 5 altsettings (AltSet 1,2,3,4,5) except:
254 * Interface 3 (Digital Out) has an extra Alset nb.6
255 * Interface 5 (Digital In) does not have Alset nb.3 and 5
257 Here is a short description of the AltSettings capabilities:
258 * AltSettings 1 corresponds to
259 - 24-bit depth, 48.1-96kHz sample mode
260 - Adaptive playback (Ao and Do), Synch capture (Ai), or Asynch capture (Di)
261 * AltSettings 2 corresponds to
262 - 24-bit depth, 8-48kHz sample mode
263 - Asynch capture and playback (Ao,Ai,Do,Di)
264 * AltSettings 3 corresponds to
265 - 24-bit depth, 8-48kHz sample mode
266 - Synch capture (Ai) and Adaptive playback (Ao,Do)
267 * AltSettings 4 corresponds to
268 - 16-bit depth, 8-48kHz sample mode
269 - Asynch capture and playback (Ao,Ai,Do,Di)
270 * AltSettings 5 corresponds to
271 - 16-bit depth, 8-48kHz sample mode
272 - Synch capture (Ai) and Adaptive playback (Ao,Do)
273 * AltSettings 6 corresponds to
274 - 16-bit depth, 8-48kHz sample mode
275 - Synch playback (Do), audio format type III IEC1937_AC-3
277 In order to ensure a correct intialization of the device, the driver
278 _must_know_ how the device will be used:
279 * if DTS is choosen, only Interface 2 with AltSet nb.6 must be
281 * if 96KHz only AltSets nb.1 of each interface must be selected
282 * if samples are using 24bits/48KHz then AltSet 2 must me used if
283 Digital input is connected, and only AltSet nb.3 if Digital input
285 * if samples are using 16bits/48KHz then AltSet 4 must me used if
286 Digital input is connected, and only AltSet nb.5 if Digital input
289 When device_setup is given as a parameter to the snd-usb-audio module, the
290 parse_audio_enpoint function uses a quirk called
291 "audiophile_skip_setting_quirk" in order to prevent AltSettings not
292 corresponding to device_setup from being registered in the driver.
294 3 - Audiophile USB and Jack support
295 ===================================
297 This section deals with support of the Audiophile USB device in Jack.
298 The main issue regarding this support is that the device is Big Endian
301 3.1 - Using the plug alsa plugin
302 --------------------------------
304 Jack doesn't directly support big endian devices. Thus, one way to have support
305 for this device with Alsa is to use the Alsa "plug" converter.
307 For instance here is one way to run Jack with 2 playback channels on Ao and 2
308 capture channels from Ai:
309 % jackd -R -dalsa -dplughw:1 -r48000 -p256 -n2 -D -Cplughw:1,1
312 However you may see the following warning message:
313 "You appear to be using the ALSA software "plug" layer, probably a result of
314 using the "default" ALSA device. This is less efficient than it could be.
315 Consider using a hardware device instead rather than using the plug layer."
318 3.2 - Patching alsa to use direct pcm device
319 -------------------------------------------
320 A patch for Jack by Andreas Steinmetz adds support for Big Endian devices.
321 However it has not been included in the CVS tree.
323 You can find it at the following URL:
324 http://sourceforge.net/tracker/index.php?func=detail&aid=1289682&group_id=39687&
327 After having applied the patch you can run jackd with the following command
329 # /usr/local/bin/jackd -R -dalsa -Phw:1,0 -r48000 -p128 -n2 -D -Chw:1,1