[alsa-devel] left/right bleed or crossover

Howdy Pierce howdy at cardinalpeak.com
Wed Jul 4 01:02:49 CEST 2007

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

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?


  Howdy Pierce
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  Cardinal Peak, LLC

  work:  (303) 665-3962 x101
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