[LAU] Jack chokes on merged device defined in .asoundrc

James Harkins jamshark70 at gmail.com
Mon Jun 18 01:58:50 UTC 2012

This is my first post to this list -- thanks in advance for advice. (Actually, I posted this first on the jackit mailing list as it seems to be a jack configuration issue, but it went ignored there for about 2.5 days so I'm trying again here.)

I'm trying to configure Jack 1.9.6 on Ubuntu 10.04 (with real-time kernel) to use all four channels of an M-Audio fast track pro. The class-compliant USB audio driver reads a pair of stereo devices:

card 1: Pro [FastTrack Pro], device 0: USB Audio [USB Audio]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
card 1: Pro [FastTrack Pro], device 1: USB Audio [USB Audio #1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

I've set up a merged device in .asoundrc and tested directly against alsa, no problem:

1. Play a stereo, 44.1 kHz, 16 bit file to hw:1,0.
2. Play the same file to hw:1,1.
3. Use SuperCollider to make a four channel version of the same file, and play this to the merged device.

All of these tests are successful -- so I think the .asoundrc configuration is correct.

Jack can use either of the stereo devices -- hw:1,0 or hw:1,1 -- for playback with no problem. I've been using that successfully for almost two years now.

But... (-Chw:1,1 is for the FTPro's stereo input)

/usr/bin/jackd -S -P60 -dalsa -r44100 -p1024 -n2 -D -Chw:1,1 -Pft4 -s

... gives me:

JACK server starting in realtime mode with priority 60
Acquire audio card Audio1
creating alsa driver ...
Using ALSA driver USB-Audio running on card 1 - M-Audio FastTrack Pro at usb-0000:00:1d.0-1.5, full speed
configuring for 44100Hz, period = 1024 frames (23.2 ms), buffer = 2 periods
ALSA: final selected sample format for capture: 16bit little-endian
ALSA: use 2 periods for capture
ALSA: final selected sample format for playback: 16bit little-endian
ALSA: use 2 periods for playback
ALSA: could not start playback (Broken pipe)
Cannot start driver
JackServer::Start() failed with -1
Released audio card Audio1
Failed to start server

Any ideas what I'm missing?


James Harkins /// dewdrop world
jamshark70 at dewdrop-world.net

"Come said the Muse,
Sing me a song no poet has yet chanted,
Sing me the universal."  -- Whitman

blog: http://www.dewdrop-world.net/words
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