[ALSA - driver 0001151]: Audigy sampling rate seems off

[bugtrack@alsa-project.org]

A NOTE has been added to this issue.
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<https://bugtrack.alsa-project.org/alsa-bug/view.php?id=1151> 
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Reported By:                felix
Assigned To:                
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Project:                    ALSA - driver
Issue ID:                   1151
Category:                   PCI - emu10k1
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
Distribution:               Suse 9.1
Kernel Version:             2.6.5-7.147-default
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Date Submitted:             06-02-2005 23:07 CEST
Last Modified:              06-03-2005 10:59 CEST
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Summary:                    Audigy sampling rate seems off
Description: 
I'm doing an experiment that involves generating a tone, sending it out
the
sound card and into a (passive) circuit, and recording from the circuit
back
into line in at the same time.

When I play a sample: mono, 8kHz sample rate, containing a synthetic 1kHz
sin signal, the recording I get is of a signal 1000.12Hz. If I send 100Hz,
I get back 100.012Hz. I use 'snd' to do a 256K-point FFT across a 10
second sample just to be sure. I've also verified this using FFTW and
correlation-based programs of my own.

I've also verified that the reference 1kHz and 100Hz signals are exact.

As a sanity check, I tried the same experiment on the built-in sound card
on that same PC. The signals come back correct.

Note the seeming coincidence that the frequency of the signal coming back
is 1/8000 higher than the signal output.

I've never seen anything like it. Not that I've been looking before...
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----------------------------------------------------------------------
 sst4 - 06-03-05 00:29 
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If it's rather off by 1/8192 (8192 is 2 to 13th power), then it'd look very
much programmatic.

Just an observation - I know nothing about "audigy".

----------------------------------------------------------------------
 perex - 06-03-05 10:59 
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Note that the routine which calculates "pitch" for playback is in
alsa-kernel/pci/emu10k1/emupcm.c - emu10k1_calc_pitch_target(). It's quite
simple, so you may do experiments with it.

Also, upgrade to latest ALSA 1.0.9, there are some cleanups for the sample
cache, and it might be also related.

Issue History
Date Modified  Username       Field                    Change              
======================================================================
06-02-05 23:07 felix          New Issue                                    
06-02-05 23:07 felix          Distribution              => Suse 9.1        
06-02-05 23:07 felix          Kernel Version            => 2.6.5-7.147-default
06-03-05 00:29 sst4           Note Added: 0004879                          
06-03-05 10:59 perex          Note Added: 0004883                          
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