#11842 NORM 12.1.0: audacity microphone monitor sometimes shows the wrong channel input

Zarro Boogs per Child bugtracker at laptop.org
Wed May 9 22:45:11 EDT 2012

#11842: audacity microphone monitor sometimes shows the wrong channel input
           Reporter:  Quozl         |       Owner:                                   
               Type:  defect        |      Status:  new                              
           Priority:  normal        |   Milestone:  12.1.0                           
          Component:  not assigned  |     Version:  Development build as of this date
         Resolution:                |    Keywords:                                   
        Next_action:  diagnose      |    Verified:  0                                
Deployment_affected:                |   Blockedby:                                   
           Blocking:                |  
Changes (by Quozl):

  * next_action:  reproduce => diagnose


 I have reproduced the symptom with audacity.

 A simpler method to reproduce is to only ''Start Monitoring'', note the
 graph response to ambient, then ''Stop Monitoring'', then ''Start
 Monitoring'' again, then note the graph response to ambient.  The first
 response is on the right channel, the second response is on the left

 The symptom only occurs on the first open of the microphone since boot.

 I have not reproduced the symptom using arecord only, and internal

 arecord -c 2 -r 48000 -d 6 a.wav
 arecord -c 2 -r 48000 -d 6 b.wav
 arecord -c 2 -r 48000 -d 6 c.wav
 aplay c.wav
 arecord -c 2 -r 48000 -d 6 d.wav

 In each recording, the data appears only in the right channel.  This is
 inconsistent with the wiring of the internal microphone to the left
 channel of the codec, but my point is that it doesn't change channels over
 use of arecord and aplay.

 However, starting audacity at this point, ''Start Monitoring'', then
 record a sample, then terminating audacity ... results in the next arecord
 recording occupying the left channel.  It is as if something that audacity
 has done causes the signal routing to change.  I have not looked for other
 actions that might cause this change.

 The amixer transitions are only that the ''MIC Bias'' control turns on
 while monitoring is active.  So it isn't an ALSA mixer control effect.

Ticket URL: <http://dev.laptop.org/ticket/11842#comment:3>
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