Re: Noise on resume [was Audio CDs in xmms on ibook2 2001 600Mhz]
On Sat, Mar 09, 2002 at 05:21:26PM -0500, Christopher C. Chimelis wrote:
>
> On Sat, 9 Mar 2002, Will Aoki wrote:
>
> > Another thing I've noticed is that sometimes, on resume, the computer
> > will play loud clicks through the speakers. Suspending again and resuming
> > sometimes works to make the clicking go away, but once it's happened,
> > it tends to happen again unless I unload and reload the audio driver.
> > It's pretty rare - it's only happened twice since my laptop was last
> > rebooted on Jan 9.
> >
> > I've seen mention of the clicks-on-resume occasionally on the mailing
> > list, but I don't recall seeing a fix.
>
> That's because I've been totally unable to reproduce this. I've tried at
> least 50 times, but never could get this to happen on my Tibook.
It's finally happened again, but this time I had a tape recorder,
headphones, and time to experiment. I'll report my results for the
record:
* What I heard didn't sound like a normal feedback whistle - it was
distinct clicking, which my unscientific timing made out to be
somewhere between 3 and 7 Hz. There was an occasional whistle, but
not that loud, and it didn't stay.
* The noise goes away if I connect something to the headphone jack.
I don't hear the noise through the speakers or the headphones, but
I do hear noise through the headphones that sounds somewhat like
the noise from my hard disk. I negelcted to check whether tapping
the microphone produced noise on the headphones, but I'll check
next time it happens.
* From past experimentation, making noise into or keeping noise from
the microphone has a small effect on the noise coming from the
speakers.
* The clicks comes back when I disconnect the headphones.
* The sound driver produces no errors if programs try using the sound
device.
* Adjusting the mixer has no effect on audio output.
* Playing sounds (to /dev/dsp) had no effect on audio output - the
sounds weren't audible, either on headphones or speaker.
* A suspend and resume cycle made it go away. The audio driver
funcionted normally - I could play sounds, and adjusting the mixer
affected the volume in the expected manner.
The system is still running 2.4.17-ben0, as I haven't rebooted it since
January. The sound driver module has been loaded since last Friday, when
I wanted to play Q2 while waiting at the dentist's. The underlying
hardware is a first-generation ibook2 (aka "iBook 2001 Dual USB").
I'm likely to rsync, build and boot a new kernel tomorrow, and if I do so,
I'll try to reproduce the clicking again.
I tried about forty more suspend-resume cycles afterward, of which only
one resulted in clicks. I hate transient faults - they're such a pain
to debug :\
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