[LAU] Problems connecting Sound Devices usbpre2 to JACK

robertlazarski robertlazarski at gmail.com
Fri Apr 23 20:02:25 CEST 2021

I have a lot of hardware, including several Tentacle Sync units that send
LTC audio to cameras. I need to connect this audio to Linux for some MTC
coding in C/C++ of midi events for "live in the studio" performances.

I am a little rusty in my Linux Audio skills. I seem to have this interface
ready to go with Jack but I get no sound of the LTC from my internal
speakers with or without Jack. I am running OpenSuse leap 15.

I have two shells open, one with a Jack Session and one with jltcdump. The
jack command does change the display on the interface. I couldn't get
qjackctl to recognize the usb interface, only the default intel sound
devices. Audacity doesn't see the device. Any ideas?

Shell 1:

 /root> cat /proc/asound/cards
 0 [PCH            ]: HDA-Intel - HDA Intel PCH
                      HDA Intel PCH at 0xed128000 irq 141
 1 [USBPre2        ]: USB-Audio - USBPre2
                      Sound Devices USBPre2 at usb-0000:00:14.0-1, high
 /root> jackd -d alsa -d hw:USBPre2
jackdmp 1.9.12
Copyright 2001-2005 Paul Davis and others.
Copyright 2004-2016 Grame.
Copyright 2016-2017 Filipe Coelho.
jackdmp comes with ABSOLUTELY NO WARRANTY
This is free software, and you are welcome to redistribute it
under certain conditions; see the file COPYING for details
no message buffer overruns
no message buffer overruns
no message buffer overruns
JACK server starting in realtime mode with priority 10
self-connect-mode is "Don't restrict self connect requests"
Acquire audio card Audio1
creating alsa driver ...
configuring for 48000Hz, period = 1024 frames (21.3 ms), buffer = 2 periods
ALSA: final selected sample format for capture: 24bit little-endian in
3bytes format
ALSA: use 2 periods for capture
ALSA: final selected sample format for playback: 24bit little-endian in
3bytes format
ALSA: use 2 periods for playback

Shell #2, does nothing.

 /home/robert> sudo /usr/local/bin/jltcdump
##        SMPTE        | audio-sample-num REV|             unix-system-time
##u-bits    time-code  |  start      end  ERS|       start
#Start: sample: 0 tme: 0.000000000
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