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1========================================================2Guide to using M-Audio Audiophile USB with ALSA and Jack3========================================================4 5v1.56 7Thibault Le Meur <Thibault.LeMeur@supelec.fr>8 9This document is a guide to using the M-Audio Audiophile USB (tm) device with 10ALSA and JACK.11 12History13=======14 15* v1.4 - Thibault Le Meur (2007-07-11)16 17 - Added Low Endianness nature of 16bits-modes18 found by Hakan Lennestal <Hakan.Lennestal@brfsodrahamn.se>19 - Modifying document structure20 21* v1.5 - Thibault Le Meur (2007-07-12)22 - Added AC3/DTS passthru info23 24 25Audiophile USB Specs and correct usage26======================================27 28This part is a reminder of important facts about the functions and limitations 29of the device.30 31The device has 4 audio interfaces, and 2 MIDI ports:32 33 * Analog Stereo Input (Ai)34 35 - This port supports 2 pairs of line-level audio inputs (1/4" TS and RCA) 36 - When the 1/4" TS (jack) connectors are connected, the RCA connectors37 are disabled38 39 * Analog Stereo Output (Ao)40 * Digital Stereo Input (Di)41 * Digital Stereo Output (Do)42 * Midi In (Mi)43 * Midi Out (Mo)44 45The internal DAC/ADC has the following characteristics:46 47* sample depth of 16 or 24 bits48* sample rate from 8kHz to 96kHz49* Two interfaces can't use different sample depths at the same time.50 51Moreover, the Audiophile USB documentation gives the following Warning:52 Please exit any audio application running before switching between bit depths53 54Due to the USB 1.1 bandwidth limitation, a limited number of interfaces can be 55activated at the same time depending on the audio mode selected:56 57 * 16-bit/48kHz ==> 4 channels in + 4 channels out58 59 - Ai+Ao+Di+Do60 61 * 24-bit/48kHz ==> 4 channels in + 2 channels out, 62 or 2 channels in + 4 channels out63 64 - Ai+Ao+Do or Ai+Di+Ao or Ai+Di+Do or Di+Ao+Do65 66 * 24-bit/96kHz ==> 2 channels in _or_ 2 channels out (half duplex only)67 68 - Ai or Ao or Di or Do69 70Important facts about the Digital interface:71--------------------------------------------72 73 * The Do port additionally supports surround-encoded AC-3 and DTS passthrough, 74 though I haven't tested it under Linux75 76 - Note that in this setup only the Do interface can be enabled77 78 * Apart from recording an audio digital stream, enabling the Di port is a way 79 to synchronize the device to an external sample clock80 81 - As a consequence, the Di port must be enable only if an active Digital 82 source is connected83 - Enabling Di when no digital source is connected can result in a 84 synchronization error (for instance sound played at an odd sample rate)85 86 87Audiophile USB MIDI support in ALSA88===================================89 90The Audiophile USB MIDI ports will be automatically supported once the91following modules have been loaded:92 93 * snd-usb-audio94 * snd-seq-midi95 96No additional setting is required.97 98 99Audiophile USB Audio support in ALSA100====================================101 102Audio functions of the Audiophile USB device are handled by the snd-usb-audio 103module. This module can work in a default mode (without any device-specific 104parameter), or in an "advanced" mode with the device-specific parameter called 105``device_setup``.106 107Default Alsa driver mode108------------------------109 110The default behavior of the snd-usb-audio driver is to list the device 111capabilities at startup and activate the required mode when required 112by the applications: for instance if the user is recording in a 11324bit-depth-mode and immediately after wants to switch to a 16bit-depth mode,114the snd-usb-audio module will reconfigure the device on the fly.115 116This approach has the advantage to let the driver automatically switch from sample 117rates/depths automatically according to the user's needs. However, those who 118are using the device under windows know that this is not how the device is meant to119work: under windows applications must be closed before using the m-audio control120panel to switch the device working mode. Thus as we'll see in next section, this 121Default Alsa driver mode can lead to device misconfigurations.122 123Let's get back to the Default Alsa driver mode for now. In this case the 124Audiophile interfaces are mapped to alsa pcm devices in the following 125way (I suppose the device's index is 1):126 127 * hw:1,0 is Ao in playback and Di in capture128 * hw:1,1 is Do in playback and Ai in capture129 * hw:1,2 is Do in AC3/DTS passthrough mode130 131In this mode, the device uses Big Endian byte-encoding so that 132supported audio format are S16_BE for 16-bit depth modes and S24_3BE for 13324-bits depth mode.134 135One exception is the hw:1,2 port which was reported to be Little Endian 136compliant (supposedly supporting S16_LE) but processes in fact only S16_BE streams.137This has been fixed in kernel 2.6.23 and above and now the hw:1,2 interface 138is reported to be big endian in this default driver mode.139 140Examples:141 142 * playing a S24_3BE encoded raw file to the Ao port::143 144 % aplay -D hw:1,0 -c2 -t raw -r48000 -fS24_3BE test.raw145 146 * recording a S24_3BE encoded raw file from the Ai port::147 148 % arecord -D hw:1,1 -c2 -t raw -r48000 -fS24_3BE test.raw149 150 * playing a S16_BE encoded raw file to the Do port::151 152 % aplay -D hw:1,1 -c2 -t raw -r48000 -fS16_BE test.raw153 154 * playing an ac3 sample file to the Do port::155 156 % aplay -D hw:1,2 --channels=6 ac3_S16_BE_encoded_file.raw157 158If you're happy with the default Alsa driver mode and don't experience any 159issue with this mode, then you can skip the following chapter.160 161Advanced module setup162---------------------163 164Due to the hardware constraints described above, the device initialization made 165by the Alsa driver in default mode may result in a corrupted state of the 166device. For instance, a particularly annoying issue is that the sound captured 167from the Ai interface sounds distorted (as if boosted with an excessive high168volume gain).169 170For people having this problem, the snd-usb-audio module has a new module 171parameter called ``device_setup`` (this parameter was introduced in kernel172release 2.6.17)173 174Initializing the working mode of the Audiophile USB175~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~176 177As far as the Audiophile USB device is concerned, this value let the user 178specify:179 180 * the sample depth181 * the sample rate182 * whether the Di port is used or not 183 184When initialized with ``device_setup=0x00``, the snd-usb-audio module has185the same behaviour as when the parameter is omitted (see paragraph "Default 186Alsa driver mode" above)187 188Others modes are described in the following subsections.189 19016-bit modes191~~~~~~~~~~~~192 193The two supported modes are:194 195 * ``device_setup=0x01``196 197 - 16bits 48kHz mode with Di disabled198 - Ai,Ao,Do can be used at the same time199 - hw:1,0 is not available in capture mode200 - hw:1,2 is not available201 202 * ``device_setup=0x11``203 204 - 16bits 48kHz mode with Di enabled205 - Ai,Ao,Di,Do can be used at the same time206 - hw:1,0 is available in capture mode207 - hw:1,2 is not available208 209In this modes the device operates only at 16bits-modes. Before kernel 2.6.23,210the devices where reported to be Big-Endian when in fact they were Little-Endian211so that playing a file was a matter of using:212::213 214 % aplay -D hw:1,1 -c2 -t raw -r48000 -fS16_BE test_S16_LE.raw215 216where "test_S16_LE.raw" was in fact a little-endian sample file.217 218Thanks to Hakan Lennestal (who discovered the Little-Endiannes of the device in219these modes) a fix has been committed (expected in kernel 2.6.23) and220Alsa now reports Little-Endian interfaces. Thus playing a file now is as simple as221using:222::223 224 % aplay -D hw:1,1 -c2 -t raw -r48000 -fS16_LE test_S16_LE.raw225 226 22724-bit modes228~~~~~~~~~~~~229 230The three supported modes are:231 232 * ``device_setup=0x09``233 234 - 24bits 48kHz mode with Di disabled235 - Ai,Ao,Do can be used at the same time236 - hw:1,0 is not available in capture mode237 - hw:1,2 is not available238 239 * ``device_setup=0x19``240 241 - 24bits 48kHz mode with Di enabled242 - 3 ports from {Ai,Ao,Di,Do} can be used at the same time243 - hw:1,0 is available in capture mode and an active digital source must be 244 connected to Di245 - hw:1,2 is not available246 247 * ``device_setup=0x0D`` or ``0x10``248 249 - 24bits 96kHz mode250 - Di is enabled by default for this mode but does not need to be connected 251 to an active source252 - Only 1 port from {Ai,Ao,Di,Do} can be used at the same time253 - hw:1,0 is available in captured mode254 - hw:1,2 is not available255 256In these modes the device is only Big-Endian compliant (see "Default Alsa driver 257mode" above for an aplay command example)258 259AC3 w/ DTS passthru mode260~~~~~~~~~~~~~~~~~~~~~~~~261 262Thanks to Hakan Lennestal, I now have a report saying that this mode works.263 264 * ``device_setup=0x03``265 266 - 16bits 48kHz mode with only the Do port enabled 267 - AC3 with DTS passthru268 - Caution with this setup the Do port is mapped to the pcm device hw:1,0269 270The command line used to playback the AC3/DTS encoded .wav-files in this mode:271::272 273 % aplay -D hw:1,0 --channels=6 ac3_S16_LE_encoded_file.raw274 275How to use the ``device_setup`` parameter276~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~277 278The parameter can be given:279 280 * By manually probing the device (as root):::281 282 # modprobe -r snd-usb-audio283 # modprobe snd-usb-audio index=1 device_setup=0x09284 285 * Or while configuring the modules options in your modules configuration file286 (typically a .conf file in /etc/modprobe.d/ directory:::287 288 alias snd-card-1 snd-usb-audio289 options snd-usb-audio index=1 device_setup=0x09290 291CAUTION when initializing the device292-------------------------------------293 294 * Correct initialization on the device requires that device_setup is given to295 the module BEFORE the device is turned on. So, if you use the "manual probing"296 method described above, take care to power-on the device AFTER this initialization.297 298 * Failing to respect this will lead to a misconfiguration of the device. In this case299 turn off the device, unprobe the snd-usb-audio module, then probe it again with300 correct device_setup parameter and then (and only then) turn on the device again.301 302 * If you've correctly initialized the device in a valid mode and then want to switch303 to another mode (possibly with another sample-depth), please use also the following 304 procedure:305 306 - first turn off the device307 - de-register the snd-usb-audio module (modprobe -r)308 - change the device_setup parameter by changing the device_setup309 option in ``/etc/modprobe.d/*.conf``310 - turn on the device311 312 * A workaround for this last issue has been applied to kernel 2.6.23, but it may not313 be enough to ensure the 'stability' of the device initialization.314 315Technical details for hackers316-----------------------------317 318This section is for hackers, wanting to understand details about the device319internals and how Alsa supports it.320 321Audiophile USB's ``device_setup`` structure322~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~323 324If you want to understand the device_setup magic numbers for the Audiophile 325USB, you need some very basic understanding of binary computation. However, 326this is not required to use the parameter and you may skip this section.327 328The device_setup is one byte long and its structure is the following:329::330 331 +---+---+---+---+---+---+---+---+332 | b7| b6| b5| b4| b3| b2| b1| b0|333 +---+---+---+---+---+---+---+---+334 | 0 | 0 | 0 | Di|24B|96K|DTS|SET|335 +---+---+---+---+---+---+---+---+336 337Where:338 339 * b0 is the ``SET`` bit340 341 - it MUST be set if device_setup is initialized 342 343 * b1 is the ``DTS`` bit344 345 - it is set only for Digital output with DTS/AC3346 - this setup is not tested347 348 * b2 is the Rate selection flag349 350 - When set to ``1`` the rate range is 48.1-96kHz351 - Otherwise the sample rate range is 8-48kHz352 353 * b3 is the bit depth selection flag354 355 - When set to ``1`` samples are 24bits long356 - Otherwise they are 16bits long357 - Note that b2 implies b3 as the 96kHz mode is only supported for 24 bits 358 samples359 360 * b4 is the Digital input flag361 362 - When set to ``1`` the device assumes that an active digital source is 363 connected 364 - You shouldn't enable Di if no source is seen on the port (this leads to 365 synchronization issues)366 - b4 is implied by b2 (since only one port is enabled at a time no synch 367 error can occur) 368 369 * b5 to b7 are reserved for future uses, and must be set to ``0``370 371 - might become Ao, Do, Ai, for b7, b6, b4 respectively372 373Caution:374 375 * there is no check on the value you will give to device_setup376 377 - for instance choosing 0x05 (16bits 96kHz) will fail back to 0x09 since 378 b2 implies b3. But _there_will_be_no_warning_ in /var/log/messages379 380 * Hardware constraints due to the USB bus limitation aren't checked381 382 - choosing b2 will prepare all interfaces for 24bits/96kHz but you'll383 only be able to use one at the same time384 385USB implementation details for this device386~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~387 388You may safely skip this section if you're not interested in driver 389hacking.390 391This section describes some internal aspects of the device and summarizes the 392data I got by usb-snooping the windows and Linux drivers.393 394The M-Audio Audiophile USB has 7 USB Interfaces:395a "USB interface":396 397 * USB Interface nb.0398 * USB Interface nb.1399 400 - Audio Control function401 402 * USB Interface nb.2403 404 - Analog Output405 406 * USB Interface nb.3407 408 - Digital Output409 410 * USB Interface nb.4411 412 - Analog Input413 414 * USB Interface nb.5415 416 - Digital Input417 418 * USB Interface nb.6419 420 - MIDI interface compliant with the MIDIMAN quirk 421 422Each interface has 5 altsettings (AltSet 1,2,3,4,5) except:423 424 * Interface 3 (Digital Out) has an extra Alset nb.6 425 * Interface 5 (Digital In) does not have Alset nb.3 and 5 426 427Here is a short description of the AltSettings capabilities:428 429* AltSettings 1 corresponds to430 431 - 24-bit depth, 48.1-96kHz sample mode432 - Adaptive playback (Ao and Do), Synch capture (Ai), or Asynch capture (Di)433 434* AltSettings 2 corresponds to435 436 - 24-bit depth, 8-48kHz sample mode437 - Asynch capture and playback (Ao,Ai,Do,Di)438 439* AltSettings 3 corresponds to440 441 - 24-bit depth, 8-48kHz sample mode442 - Synch capture (Ai) and Adaptive playback (Ao,Do)443 444* AltSettings 4 corresponds to445 446 - 16-bit depth, 8-48kHz sample mode447 - Asynch capture and playback (Ao,Ai,Do,Di)448 449* AltSettings 5 corresponds to450 451 - 16-bit depth, 8-48kHz sample mode452 - Synch capture (Ai) and Adaptive playback (Ao,Do)453 454* AltSettings 6 corresponds to455 456 - 16-bit depth, 8-48kHz sample mode457 - Synch playback (Do), audio format type III IEC1937_AC-3458 459In order to ensure a correct initialization of the device, the driver 460*must* *know* how the device will be used:461 462 * if DTS is chosen, only Interface 2 with AltSet nb.6 must be463 registered464 * if 96KHz only AltSets nb.1 of each interface must be selected465 * if samples are using 24bits/48KHz then AltSet 2 must me used if466 Digital input is connected, and only AltSet nb.3 if Digital input467 is not connected468 * if samples are using 16bits/48KHz then AltSet 4 must me used if469 Digital input is connected, and only AltSet nb.5 if Digital input470 is not connected471 472When device_setup is given as a parameter to the snd-usb-audio module, the 473parse_audio_endpoints function uses a quirk called 474``audiophile_skip_setting_quirk`` in order to prevent AltSettings not 475corresponding to device_setup from being registered in the driver.476 477Audiophile USB and Jack support478===============================479 480This section deals with support of the Audiophile USB device in Jack.481 482There are 2 main potential issues when using Jackd with the device:483 484* support for Big-Endian devices in 24-bit modes485* support for 4-in / 4-out channels486 487Direct support in Jackd488-----------------------489 490Jack supports big endian devices only in recent versions (thanks to491Andreas Steinmetz for his first big-endian patch). I can't remember 492exactly when this support was released into jackd, let's just say that493with jackd version 0.103.0 it's almost ok (just a small bug is affecting 49416bits Big-Endian devices, but since you've read carefully the above495paragraphs, you're now using kernel >= 2.6.23 and your 16bits devices 496are now Little Endians ;-) ).497 498You can run jackd with the following command for playback with Ao and499record with Ai:500::501 502 % jackd -R -dalsa -Phw:1,0 -r48000 -p128 -n2 -D -Chw:1,1503 504Using Alsa plughw505-----------------506 507If you don't have a recent Jackd installed, you can downgrade to using508the Alsa ``plug`` converter.509 510For instance here is one way to run Jack with 2 playback channels on Ao and 2 511capture channels from Ai:512::513 514 % jackd -R -dalsa -dplughw:1 -r48000 -p256 -n2 -D -Cplughw:1,1515 516However you may see the following warning message:517 You appear to be using the ALSA software "plug" layer, probably a result of 518 using the "default" ALSA device. This is less efficient than it could be. 519 Consider using a hardware device instead rather than using the plug layer.520 521Getting 2 input and/or output interfaces in Jack522------------------------------------------------523 524As you can see, starting the Jack server this way will only enable 1 stereo525input (Di or Ai) and 1 stereo output (Ao or Do).526 527This is due to the following restrictions:528 529* Jack can only open one capture device and one playback device at a time530* The Audiophile USB is seen as 2 (or three) Alsa devices: hw:1,0, hw:1,1531 (and optionally hw:1,2)532 533If you want to get Ai+Di and/or Ao+Do support with Jack, you would need to534combine the Alsa devices into one logical "complex" device.535 536If you want to give it a try, I recommend reading the information from537this page: http://www.sound-man.co.uk/linuxaudio/ice1712multi.html538It is related to another device (ice1712) but can be adapted to suit539the Audiophile USB.540 541Enabling multiple Audiophile USB interfaces for Jackd will certainly require:542 543* Making sure your Jackd version has the MMAP_COMPLEX patch (see the ice1712 page)544* (maybe) patching the alsa-lib/src/pcm/pcm_multi.c file (see the ice1712 page)545* define a multi device (combination of hw:1,0 and hw:1,1) in your .asoundrc546 file 547* start jackd with this device548 549I had no success in testing this for now, if you have any success with this kind 550of setup, please drop me an email.551