us122 woes

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us122 woes

Julian Squires

Hi, jackit-devel.

I'm having some problems with my Tascam US-122 and jack, on a powerpc
mac mini.  When I run jackd with -S, everything works fine, and I have
been using ardour and so on quite happily with that mode.  When I try
using 32-bit mode, I get extremely loud noise (constantly clipping)
from the capture ports, no matter what's going on.

Curiously, when I use jackrec with -b 24, it seems to record fine[1],
but when I use -b 32, it produces intermittent (but rapid) noise[2].
(jackrec -f foo.wav -d 1 -b {24,32} system:capture_1 system:capture_2
for both of those files; beware, the second one is obviously very

Originally I thought this was a byte swapping issue, but I've verified
that quirk_bswap is being set to one, which appears to be the correct
behavior here -- I've also tried hard coding it to zero, which seems
to behave similarly.

Here's the output of jackd running when I captured those two samples:
(it's the current svn of jack, with a jack_error added to emit the
value of quirk_bswap for my own verification)

julian@onion:~/jack% ./jackd/jackd -R -d alsa -d hw:1 -r 44100 -p 4096 -n 2 -H -M
jackd 0.107.4
Copyright 2001-2005 Paul Davis and others.
This is free software, and you are welcome to redistribute it
under certain conditions; see the file COPYING for details

JACK compiled with System V SHM support.
loading driver ..
apparent rate = 44100
creating alsa driver ... hw:1|hw:1|4096|2|44100|0|0|hwmon|hwmeter|-|32bit
control device hw:1
configuring for 44100Hz, period = 4096 frames, buffer = 2 periods
quirk_bswap : 1
ALSA: final selected sample format for capture: 24bit little-endian
ALSA: use 2 periods for capture
quirk_bswap : 1
ALSA: final selected sample format for playback: 24bit little-endian
ALSA: use 2 periods for playback

I'm using this machine only for studio recording, no realtime
performance or monitoring, so latency doesn't matter at all to me, so
normally I use a period of 4096 frames.  I've tried with a variety of
other settings, though, to no apparent improvement.  I'm pretty sure
-r 48000 behaves the same, too.

I've also tried using the rawusb mode instead; originally I was going
to write that the behavior is basically the same, but when I just
tried it then, I got:

jackd watchdog: timeout - killing jackd
zsh: abort (core dumped)  ./jackd/jackd -R -d alsa -d hw:1,2 -r 44100 -p 4096 -n 2 -H -M

when I tried to record the 24-bit sample.  (the 32-bit sample is much
like in generic mode, see [3])  Stupidly, I deleted the core file
habitually, and then when I tried it again, it didn't do it again.
But the 24-bit file, this time, is bursts of noise punctuated with

I'm happy to try and fix the problem myself, but I'm hoping someone
out there might have some ideas of what I can try next.  I spent a
little while reading the jack source, but I haven't yet had the time
to invest to figure out what jackrec -d 24 is doing differently, and
more importantly, whether I could switch ardour into a similar mode.

I don't think this has any relation with the US-122 problems
reported by Matt Savigear earlier, but it's possible.



Julian Squires

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