1 Guide to using M-Audio Audiophile USB with ALSA and Jack v1.5 2 ======================================================== 3 4 Thibault Le Meur <Thibault.LeMeur@supelec.fr> 5 6This document is a guide to using the M-Audio Audiophile USB (tm) device with 7ALSA and JACK. 8 9History 10======= 11* v1.4 - Thibault Le Meur (2007-07-11) 12 - Added Low Endianness nature of 16bits-modes 13 found by Hakan Lennestal <Hakan.Lennestal@brfsodrahamn.se> 14 - Modifying document structure 15* v1.5 - Thibault Le Meur (2007-07-12) 16 - Added AC3/DTS passthru info 17 18 191 - Audiophile USB Specs and correct usage 20========================================== 21 22This part is a reminder of important facts about the functions and limitations 23of the device. 24 25The device has 4 audio interfaces, and 2 MIDI ports: 26 * Analog Stereo Input (Ai) 27 - This port supports 2 pairs of line-level audio inputs (1/4" TS and RCA) 28 - When the 1/4" TS (jack) connectors are connected, the RCA connectors 29 are disabled 30 * Analog Stereo Output (Ao) 31 * Digital Stereo Input (Di) 32 * Digital Stereo Output (Do) 33 * Midi In (Mi) 34 * Midi Out (Mo) 35 36The internal DAC/ADC has the following characteristics: 37* sample depth of 16 or 24 bits 38* sample rate from 8kHz to 96kHz 39* Two interfaces can't use different sample depths at the same time. 40Moreover, the Audiophile USB documentation gives the following Warning: 41"Please exit any audio application running before switching between bit depths" 42 43Due to the USB 1.1 bandwidth limitation, a limited number of interfaces can be 44activated at the same time depending on the audio mode selected: 45 * 16-bit/48kHz ==> 4 channels in + 4 channels out 46 - Ai+Ao+Di+Do 47 * 24-bit/48kHz ==> 4 channels in + 2 channels out, 48 or 2 channels in + 4 channels out 49 - Ai+Ao+Do or Ai+Di+Ao or Ai+Di+Do or Di+Ao+Do 50 * 24-bit/96kHz ==> 2 channels in _or_ 2 channels out (half duplex only) 51 - Ai or Ao or Di or Do 52 53Important facts about the Digital interface: 54-------------------------------------------- 55 * The Do port additionally supports surround-encoded AC-3 and DTS passthrough, 56though I haven't tested it under Linux 57 - Note that in this setup only the Do interface can be enabled 58 * Apart from recording an audio digital stream, enabling the Di port is a way 59to synchronize the device to an external sample clock 60 - As a consequence, the Di port must be enable only if an active Digital 61source is connected 62 - Enabling Di when no digital source is connected can result in a 63synchronization error (for instance sound played at an odd sample rate) 64 65 662 - Audiophile USB MIDI support in ALSA 67======================================= 68 69The Audiophile USB MIDI ports will be automatically supported once the 70following modules have been loaded: 71 * snd-usb-audio 72 * snd-seq-midi 73 74No additional setting is required. 75 76 773 - Audiophile USB Audio support in ALSA 78======================================== 79 80Audio functions of the Audiophile USB device are handled by the snd-usb-audio 81module. This module can work in a default mode (without any device-specific 82parameter), or in an "advanced" mode with the device-specific parameter called 83"device_setup". 84 853.1 - Default Alsa driver mode 86------------------------------ 87 88The default behavior of the snd-usb-audio driver is to list the device 89capabilities at startup and activate the required mode when required 90by the applications: for instance if the user is recording in a 9124bit-depth-mode and immediately after wants to switch to a 16bit-depth mode, 92the snd-usb-audio module will reconfigure the device on the fly. 93 94This approach has the advantage to let the driver automatically switch from sample 95rates/depths automatically according to the user's needs. However, those who 96are using the device under windows know that this is not how the device is meant to 97work: under windows applications must be closed before using the m-audio control 98panel to switch the device working mode. Thus as we'll see in next section, this 99Default Alsa driver mode can lead to device misconfigurations. 100 101Let's get back to the Default Alsa driver mode for now. In this case the 102Audiophile interfaces are mapped to alsa pcm devices in the following 103way (I suppose the device's index is 1): 104 * hw:1,0 is Ao in playback and Di in capture 105 * hw:1,1 is Do in playback and Ai in capture 106 * hw:1,2 is Do in AC3/DTS passthrough mode 107 108In this mode, the device uses Big Endian byte-encoding so that 109supported audio format are S16_BE for 16-bit depth modes and S24_3BE for 11024-bits depth mode. 111 112One exception is the hw:1,2 port which was reported to be Little Endian 113compliant (supposedly supporting S16_LE) but processes in fact only S16_BE streams. 114This has been fixed in kernel 2.6.23 and above and now the hw:1,2 interface 115is reported to be big endian in this default driver mode. 116 117Examples: 118 * playing a S24_3BE encoded raw file to the Ao port 119 % aplay -D hw:1,0 -c2 -t raw -r48000 -fS24_3BE test.raw 120 * recording a S24_3BE encoded raw file from the Ai port 121 % arecord -D hw:1,1 -c2 -t raw -r48000 -fS24_3BE test.raw 122 * playing a S16_BE encoded raw file to the Do port 123 % aplay -D hw:1,1 -c2 -t raw -r48000 -fS16_BE test.raw 124 * playing an ac3 sample file to the Do port 125 % aplay -D hw:1,2 --channels=6 ac3_S16_BE_encoded_file.raw 126 127If you're happy with the default Alsa driver mode and don't experience any 128issue with this mode, then you can skip the following chapter. 129 1303.2 - Advanced module setup 131--------------------------- 132 133Due to the hardware constraints described above, the device initialization made 134by the Alsa driver in default mode may result in a corrupted state of the 135device. For instance, a particularly annoying issue is that the sound captured 136from the Ai interface sounds distorted (as if boosted with an excessive high 137volume gain). 138 139For people having this problem, the snd-usb-audio module has a new module 140parameter called "device_setup" (this parameter was introduced in kernel 141release 2.6.17) 142 1433.2.1 - Initializing the working mode of the Audiophile USB 144 145As far as the Audiophile USB device is concerned, this value let the user 146specify: 147 * the sample depth 148 * the sample rate 149 * whether the Di port is used or not 150 151When initialized with "device_setup=0x00", the snd-usb-audio module has 152the same behaviour as when the parameter is omitted (see paragraph "Default 153Alsa driver mode" above) 154 155Others modes are described in the following subsections. 156 1573.2.1.1 - 16-bit modes 158 159The two supported modes are: 160 161 * device_setup=0x01 162 - 16bits 48kHz mode with Di disabled 163 - Ai,Ao,Do can be used at the same time 164 - hw:1,0 is not available in capture mode 165 - hw:1,2 is not available 166 167 * device_setup=0x11 168 - 16bits 48kHz mode with Di enabled 169 - Ai,Ao,Di,Do can be used at the same time 170 - hw:1,0 is available in capture mode 171 - hw:1,2 is not available 172 173In this modes the device operates only at 16bits-modes. Before kernel 2.6.23, 174the devices where reported to be Big-Endian when in fact they were Little-Endian 175so that playing a file was a matter of using: 176 % aplay -D hw:1,1 -c2 -t raw -r48000 -fS16_BE test_S16_LE.raw 177where "test_S16_LE.raw" was in fact a little-endian sample file. 178 179Thanks to Hakan Lennestal (who discovered the Little-Endiannes of the device in 180these modes) a fix has been committed (expected in kernel 2.6.23) and 181Alsa now reports Little-Endian interfaces. Thus playing a file now is as simple as 182using: 183 % aplay -D hw:1,1 -c2 -t raw -r48000 -fS16_LE test_S16_LE.raw 184 1853.2.1.2 - 24-bit modes 186 187The three supported modes are: 188 189 * device_setup=0x09 190 - 24bits 48kHz mode with Di disabled 191 - Ai,Ao,Do can be used at the same time 192 - hw:1,0 is not available in capture mode 193 - hw:1,2 is not available 194 195 * device_setup=0x19 196 - 24bits 48kHz mode with Di enabled 197 - 3 ports from {Ai,Ao,Di,Do} can be used at the same time 198 - hw:1,0 is available in capture mode and an active digital source must be 199 connected to Di 200 - hw:1,2 is not available 201 202 * device_setup=0x0D or 0x10 203 - 24bits 96kHz mode 204 - Di is enabled by default for this mode but does not need to be connected 205 to an active source 206 - Only 1 port from {Ai,Ao,Di,Do} can be used at the same time 207 - hw:1,0 is available in captured mode 208 - hw:1,2 is not available 209 210In these modes the device is only Big-Endian compliant (see "Default Alsa driver 211mode" above for an aplay command example) 212 2133.2.1.3 - AC3 w/ DTS passthru mode 214 215Thanks to Hakan Lennestal, I now have a report saying that this mode works. 216 217 * device_setup=0x03 218 - 16bits 48kHz mode with only the Do port enabled 219 - AC3 with DTS passthru 220 - Caution with this setup the Do port is mapped to the pcm device hw:1,0 221 222The command line used to playback the AC3/DTS encoded .wav-files in this mode: 223 % aplay -D hw:1,0 --channels=6 ac3_S16_LE_encoded_file.raw 224 2253.2.2 - How to use the device_setup parameter 226---------------------------------------------- 227 228The parameter can be given: 229 230 * By manually probing the device (as root): 231 # modprobe -r snd-usb-audio 232 # modprobe snd-usb-audio index=1 device_setup=0x09 233 234 * Or while configuring the modules options in your modules configuration file 235 - For Fedora distributions, edit the /etc/modprobe.conf file: 236 alias snd-card-1 snd-usb-audio 237 options snd-usb-audio index=1 device_setup=0x09 238 239CAUTION when initializing the device 240------------------------------------- 241 242 * Correct initialization on the device requires that device_setup is given to 243 the module BEFORE the device is turned on. So, if you use the "manual probing" 244 method described above, take care to power-on the device AFTER this initialization. 245 246 * Failing to respect this will lead to a misconfiguration of the device. In this case 247 turn off the device, unprobe the snd-usb-audio module, then probe it again with 248 correct device_setup parameter and then (and only then) turn on the device again. 249 250 * If you've correctly initialized the device in a valid mode and then want to switch 251 to another mode (possibly with another sample-depth), please use also the following 252 procedure: 253 - first turn off the device 254 - de-register the snd-usb-audio module (modprobe -r) 255 - change the device_setup parameter by changing the device_setup 256 option in /etc/modprobe.conf 257 - turn on the device 258 * A workaround for this last issue has been applied to kernel 2.6.23, but it may not 259 be enough to ensure the 'stability' of the device initialization. 260 2613.2.3 - Technical details for hackers 262------------------------------------- 263This section is for hackers, wanting to understand details about the device 264internals and how Alsa supports it. 265 2663.2.3.1 - Audiophile USB's device_setup structure 267 268If you want to understand the device_setup magic numbers for the Audiophile 269USB, you need some very basic understanding of binary computation. However, 270this is not required to use the parameter and you may skip this section. 271 272The device_setup is one byte long and its structure is the following: 273 274 +---+---+---+---+---+---+---+---+ 275 | b7| b6| b5| b4| b3| b2| b1| b0| 276 +---+---+---+---+---+---+---+---+ 277 | 0 | 0 | 0 | Di|24B|96K|DTS|SET| 278 +---+---+---+---+---+---+---+---+ 279 280Where: 281 * b0 is the "SET" bit 282 - it MUST be set if device_setup is initialized 283 * b1 is the "DTS" bit 284 - it is set only for Digital output with DTS/AC3 285 - this setup is not tested 286 * b2 is the Rate selection flag 287 - When set to "1" the rate range is 48.1-96kHz 288 - Otherwise the sample rate range is 8-48kHz 289 * b3 is the bit depth selection flag 290 - When set to "1" samples are 24bits long 291 - Otherwise they are 16bits long 292 - Note that b2 implies b3 as the 96kHz mode is only supported for 24 bits 293 samples 294 * b4 is the Digital input flag 295 - When set to "1" the device assumes that an active digital source is 296 connected 297 - You shouldn't enable Di if no source is seen on the port (this leads to 298 synchronization issues) 299 - b4 is implied by b2 (since only one port is enabled at a time no synch 300 error can occur) 301 * b5 to b7 are reserved for future uses, and must be set to "0" 302 - might become Ao, Do, Ai, for b7, b6, b4 respectively 303 304Caution: 305 * there is no check on the value you will give to device_setup 306 - for instance choosing 0x05 (16bits 96kHz) will fail back to 0x09 since 307 b2 implies b3. But _there_will_be_no_warning_ in /var/log/messages 308 * Hardware constraints due to the USB bus limitation aren't checked 309 - choosing b2 will prepare all interfaces for 24bits/96kHz but you'll 310 only be able to use one at the same time 311 3123.2.3.2 - USB implementation details for this device 313 314You may safely skip this section if you're not interested in driver 315hacking. 316 317This section describes some internal aspects of the device and summarizes the 318data I got by usb-snooping the windows and Linux drivers. 319 320The M-Audio Audiophile USB has 7 USB Interfaces: 321a "USB interface": 322 * USB Interface nb.0 323 * USB Interface nb.1 324 - Audio Control function 325 * USB Interface nb.2 326 - Analog Output 327 * USB Interface nb.3 328 - Digital Output 329 * USB Interface nb.4 330 - Analog Input 331 * USB Interface nb.5 332 - Digital Input 333 * USB Interface nb.6 334 - MIDI interface compliant with the MIDIMAN quirk 335 336Each interface has 5 altsettings (AltSet 1,2,3,4,5) except: 337 * Interface 3 (Digital Out) has an extra Alset nb.6 338 * Interface 5 (Digital In) does not have Alset nb.3 and 5 339 340Here is a short description of the AltSettings capabilities: 341 * AltSettings 1 corresponds to 342 - 24-bit depth, 48.1-96kHz sample mode 343 - Adaptive playback (Ao and Do), Synch capture (Ai), or Asynch capture (Di) 344 * AltSettings 2 corresponds to 345 - 24-bit depth, 8-48kHz sample mode 346 - Asynch capture and playback (Ao,Ai,Do,Di) 347 * AltSettings 3 corresponds to 348 - 24-bit depth, 8-48kHz sample mode 349 - Synch capture (Ai) and Adaptive playback (Ao,Do) 350 * AltSettings 4 corresponds to 351 - 16-bit depth, 8-48kHz sample mode 352 - Asynch capture and playback (Ao,Ai,Do,Di) 353 * AltSettings 5 corresponds to 354 - 16-bit depth, 8-48kHz sample mode 355 - Synch capture (Ai) and Adaptive playback (Ao,Do) 356 * AltSettings 6 corresponds to 357 - 16-bit depth, 8-48kHz sample mode 358 - Synch playback (Do), audio format type III IEC1937_AC-3 359 360In order to ensure a correct initialization of the device, the driver 361_must_know_ how the device will be used: 362 * if DTS is chosen, only Interface 2 with AltSet nb.6 must be 363 registered 364 * if 96KHz only AltSets nb.1 of each interface must be selected 365 * if samples are using 24bits/48KHz then AltSet 2 must me used if 366 Digital input is connected, and only AltSet nb.3 if Digital input 367 is not connected 368 * if samples are using 16bits/48KHz then AltSet 4 must me used if 369 Digital input is connected, and only AltSet nb.5 if Digital input 370 is not connected 371 372When device_setup is given as a parameter to the snd-usb-audio module, the 373parse_audio_endpoints function uses a quirk called 374"audiophile_skip_setting_quirk" in order to prevent AltSettings not 375corresponding to device_setup from being registered in the driver. 376 3774 - Audiophile USB and Jack support 378=================================== 379 380This section deals with support of the Audiophile USB device in Jack. 381 382There are 2 main potential issues when using Jackd with the device: 383* support for Big-Endian devices in 24-bit modes 384* support for 4-in / 4-out channels 385 3864.1 - Direct support in Jackd 387----------------------------- 388 389Jack supports big endian devices only in recent versions (thanks to 390Andreas Steinmetz for his first big-endian patch). I can't remember 391exactly when this support was released into jackd, let's just say that 392with jackd version 0.103.0 it's almost ok (just a small bug is affecting 39316bits Big-Endian devices, but since you've read carefully the above 394paragraphs, you're now using kernel >= 2.6.23 and your 16bits devices 395are now Little Endians ;-) ). 396 397You can run jackd with the following command for playback with Ao and 398record with Ai: 399 % jackd -R -dalsa -Phw:1,0 -r48000 -p128 -n2 -D -Chw:1,1 400 4014.2 - Using Alsa plughw 402----------------------- 403If you don't have a recent Jackd installed, you can downgrade to using 404the Alsa "plug" converter. 405 406For instance here is one way to run Jack with 2 playback channels on Ao and 2 407capture channels from Ai: 408 % jackd -R -dalsa -dplughw:1 -r48000 -p256 -n2 -D -Cplughw:1,1 409 410However you may see the following warning message: 411"You appear to be using the ALSA software "plug" layer, probably a result of 412using the "default" ALSA device. This is less efficient than it could be. 413Consider using a hardware device instead rather than using the plug layer." 414 4154.3 - Getting 2 input and/or output interfaces in Jack 416------------------------------------------------------ 417 418As you can see, starting the Jack server this way will only enable 1 stereo 419input (Di or Ai) and 1 stereo output (Ao or Do). 420 421This is due to the following restrictions: 422* Jack can only open one capture device and one playback device at a time 423* The Audiophile USB is seen as 2 (or three) Alsa devices: hw:1,0, hw:1,1 424 (and optionally hw:1,2) 425 426If you want to get Ai+Di and/or Ao+Do support with Jack, you would need to 427combine the Alsa devices into one logical "complex" device. 428 429If you want to give it a try, I recommend reading the information from 430this page: http://www.sound-man.co.uk/linuxaudio/ice1712multi.html 431It is related to another device (ice1712) but can be adapted to suit 432the Audiophile USB. 433 434Enabling multiple Audiophile USB interfaces for Jackd will certainly require: 435* Making sure your Jackd version has the MMAP_COMPLEX patch (see the ice1712 page) 436* (maybe) patching the alsa-lib/src/pcm/pcm_multi.c file (see the ice1712 page) 437* define a multi device (combination of hw:1,0 and hw:1,1) in your .asoundrc 438 file 439* start jackd with this device 440 441I had no success in testing this for now, if you have any success with this kind 442of setup, please drop me an email. 443