Microphone recording problem

[Alan Dayley]

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Nathan Aubrey wrote:
> 
> Try doing exactley this from a command line while in X and report back what 
> happens. 

This provided a recording that was as clean as when X is not running.
Just to be sure, exited X back to the text only command line and
listened to all the samples again.  There were some small pops in the
playback but no real difference in quality between the text only and the
terminal window in KDE command line recordings.

> Try killing artsd completely and recording.

Trying now...  After "killall artsd" and ps output showing that artsd is
no longer running, recording with KRecord still has the high pitched
whine overpowering the audible recording content.

> I had similar problems but fixed it by disabling the mic boost option and 
> lowering the speaker output volume.

In WinXP I had to turn the boost on to get acceptable recording volume.
  I don't see where to change the mic boost option on KMix or alsamixer.
  Is there some other place to look for this setting?

> I got rid of it completely later on, by 
> replacing the microphone.

Well it is a $20 headset so I don't expect the microphone to be the
best, just good enough for now.

> If it does not do it while X is shutdown, I almost 
> want to say the processor is creating interference while in X, like it is 
> running to high or something. What kind of sound card is it?

lspci -v output shows:

00:1b.0 Audio device: Intel Corporation 82801G (ICH7 Family) High
Definition Audio Controller (rev 02)
        Subsystem: Toshiba America Info Systems Unknown device ff00
        Flags: bus master, fast devsel, latency 0, IRQ 217
        Memory at d0340000 (64-bit, non-prefetchable) [size=16K]
        Capabilities: [50] Power Management version 2
        Capabilities: [60] Message Signalled Interrupts: Mask- 64bit+
Queue=0/0 Enable-
        Capabilities: [70] Express Unknown type IRQ 0
        Capabilities: [100] Virtual Channel
        Capabilities: [130] Unknown (5)

alsamixer shows "Card: HDA Intel"
WinXP reported a Realtec driver of some kind, though I don't remember
the exact wording.

The Intel website for the chipset claims that Intel "High Definition
Audio" (HDA) can send separate audio to the speakers and the headphones.
 I don't know if that comes into play here with the two microphones
since that is a feature of the hardware, not the chipset.

It is interesting that the squeal does sound like feedback but I don't
see where that would be coming from.  And, real audio feedback should be
manifest in both KRecord and the command line, I would think.

> Maybe it 
> requires the processor to handle the DSP as it doesn't have a dedicated DSP 
> on it's own and shutting down X gives the DSP better access to the processor?

I'll have to research that a bit.

> In which, try rebuilding your kernel using different preemptions or timer 
> frequency?

I would not know what to pick for values without further guidance or
education.  I also don't like the idea of a "custom" kernel since I
don't want to lose the distro feeds.

Thanks for the tips.  I'll keep slowly working on the issue.

Alan


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