- Guide to using M-Audio Audiophile USB with ALSA and Jack v1.4
+ Guide to using M-Audio Audiophile USB with ALSA and Jack v1.5
========================================================
Thibault Le Meur <Thibault.LeMeur@supelec.fr>
- 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
1 - Audiophile USB Specs and correct usage
In this mode, the device uses Big Endian byte-encoding so that
supported audio format are S16_BE for 16-bit depth modes and S24_3BE for
-24-bits depth mode. One exception is the hw:1,2 port which is reported
-to be Little Endian compliant (supposedly supporting S16_LE) but processes
-in fact only S16_BE streams.
+24-bits depth mode.
+
+One exception is the hw:1,2 port which was reported to be Little Endian
+compliant (supposedly supporting S16_LE) but processes in fact only S16_BE streams.
+This has been fixed in kernel 2.6.23 and above and now the hw:1,2 interface
+is reported to be big endian in this default driver mode.
Examples:
* playing a S24_3BE encoded raw file to the Ao port
% arecord -D hw:1,1 -c2 -t raw -r48000 -fS24_3BE test.raw
* playing a S16_BE encoded raw file to the Do port
% aplay -D hw:1,1 -c2 -t raw -r48000 -fS16_BE test.raw
+ * playing an ac3 sample file to the Do port
+ % aplay -D hw:1,2 --channels=6 ac3_S16_BE_encoded_file.raw
If you're happy with the default Alsa driver mode and don't experience any
issue with this mode, then you can skip the following chapter.
3.2.1.3 - AC3 w/ DTS passthru mode
-This mode is untested, I have no AC3 compliant device to test it. I uses:
+Thanks to Hakan Lennestal, I now have a report saying that this mode works.
* device_setup=0x03
- 16bits 48kHz mode with only the Do port enabled
- - AC3 with DTS passthru (not tested)
+ - AC3 with DTS passthru
- Caution with this setup the Do port is mapped to the pcm device hw:1,0
+The command line used to playback the AC3/DTS encoded .wav-files in this mode:
+ % aplay -D hw:1,0 --channels=6 ac3_S16_LE_encoded_file.raw
+
3.2.2 - How to use the device_setup parameter
----------------------------------------------
alias snd-card-1 snd-usb-audio
options snd-usb-audio index=1 device_setup=0x09
-CAUTION when initializaing the device
+CAUTION when initializing the device
-------------------------------------
* Correct initialization on the device requires that device_setup is given to
the module BEFORE the device is turned on. So, if you use the "manual probing"
method described above, take care to power-on the device AFTER this initialization.
- * Failing to respect this will lead in a misconfiguration of the device. In this case
- turn off the device, unproble the snd-usb-audio module, then probe it again with
+ * Failing to respect this will lead to a misconfiguration of the device. In this case
+ turn off the device, unprobe the snd-usb-audio module, then probe it again with
correct device_setup parameter and then (and only then) turn on the device again.
* If you've correctly initialized the device in a valid mode and then want to switch
Jack supports big endian devices only in recent versions (thanks to
Andreas Steinmetz for his first big-endian patch). I can't remember
-extacly when this support was released into jackd, let's just say that
+exactly when this support was released into jackd, let's just say that
with jackd version 0.103.0 it's almost ok (just a small bug is affecting
-16bits Big-Endian devices, but since you've read carefully the above
+16bits Big-Endian devices, but since you've read carefully the above
paragraphs, you're now using kernel >= 2.6.23 and your 16bits devices
are now Little Endians ;-) ).
git.openpandora.org / pandora-kernel.git / blobdiff