#7603 NORM 8.2.0 (: 2.6.25 audio performance regression

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#7603: 2.6.25 audio performance regression
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   Reporter:  dsd        |       Owner:  dilinger              
       Type:  defect     |      Status:  new                   
   Priority:  normal     |   Milestone:  8.2.0 (was Update.2)  
  Component:  kernel     |     Version:  not specified         
 Resolution:             |    Keywords:  joyride-2181:- 8.2.0:?
Next_action:  never set  |    Verified:  0                     
  Blockedby:             |    Blocking:                        
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Comment(by dsd):

 Replying to [comment:5 dsaxena]:
 > Was looking at the wrong place for the ALSA underrun messages. I ran the
 activity via "sugar-launch TamTamMini" in terminal and grabbed stdin &
 stderr to see the application log. There is definitely a correlation
 between hald running a battery status query and an ALSA underrun occurring
 on both .25 and .22 kernels.

 Agreed.

 > I definitely still hear some crackling w/o hald every so often, but they
 are not related to hald.

 Yeah. At least for me, the non-hald crackles do not occur (or occur
 extremely rarely) on 2.6.22 though. On 2.6.25 they aren't too bad, but I
 am seeing more than one every few minutes.

 > Also, I can run 'aplay <.wav file>' from the command line and not hear
 any issues on both .22 and .25 kernels even if I do:
 >
 > {{{
 > while true
 > do
 >    cat /sys/devices/platform/olpc-battery.0/power_supply/olpc-battery/*
 > done
 > }}}

 Yeah, I made the same observation earlier.

 > If I do the above while running TamTamMini, the audio is very crackly
 and there are a lot underruns (again, with both .25 and .22 kernels).

 Same here.

 > In summary, I don't think this is completely a kernel issue but has to
 do with the way that TamTam, or csound, or the combination is feeding the
 samples to the underlying device.

 The difference is that TamTam is multitracking; it is interleaved sound.
 ALSA function snd_pcm_write()

 aplay is just a simple sound stream.

 I guess a sensible place to start attacking this would be to find out why
 hald in update1 does not continually query the battery status. This is why
 we didn't have the more severe crackling before.

-- 
Ticket URL: <http://dev.laptop.org/ticket/7603#comment:6>
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