[alsa-devel] left/right bleed or crossover

[Takashi Iwai]

At Tue, 3 Jul 2007 17:02:49 -0600,
Howdy Pierce wrote:
> 
> Takashi Iwai wrote:
> > Howdy Pierce wrote:
> >> I'm encountering the following problem on Fedora Core 6 running on a Dell
> >> Optiplex 745.  This is a pretty vanilla computer with an ICH8 chipset and
> >> integrated AD1983 sound capabilities. 
> >> 
> >> I have wired up a funky line-input cable so that I have completely 
> >> separate audio sources playing on the left and right inputs.
> >> 
> >> When I either play these through to the speaker output directly (using
> >> alsamixer), or record the audio using arecord, the result is that there 
> >> is a slight bit of bleeding or crossover, so I can faintly hear the left 
> >> input on the right channel, and vice versa.  If I record a wav file and 
> >> then play it on another computer, the left/right bleeding follows the wav
> 
> >> file, so it seems that the problem is in the capture process somehow.
> >>
> >> When I install Windows XP onto the same machine, the problem disappears, 
> >> so I can rule out hardware errors.
> >> 
> >> The application I'm working on relies on being able to reliably capture 
> >> the right and left channels of audio independently.  Since the problem 
> >> can be seen using the standard arecord/aplay tools, though, I don't think
> 
> >> it's my code.
> >> 
> >> I've tried all the possible combinations inside alsamixer, and I don't 
> >> think there's anything I've messed up there.
> >
> > To investigate where the problem exists, try to use "hw" PCM first
> > without alsa-lib plugins.  If the problem still remains, it's in the
> > driver (that I don't expect since your codec dump looks sane to me).
> 
> Thanks for the response.
> 
> I assume you want me to record something with 
>     arecord --device=hw:0,0
> ?

Yes.

> The problem still exists with that command line.  Where do I need to look
> next -- the kernel driver?  Any theories as to what might be happening here?
> Has anyone seen something similar before, perhaps on other hardware?

No, I've never heard such a (software) problem on other hardwares.

What about the recording from mic input?  (You have "Mic Boost" there,
too).


Takashi