[ALSA - driver 0001914]: playing 2-channel sound on surround device uses rear speakers

[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=1914> 
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Reported By:                mru
Assigned To:                tiwai
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Project:                    ALSA - driver
Issue ID:                   1914
Category:                   PCI - cmipci
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     assigned
Distribution:               Gentoo
Kernel Version:             2.6.15-gentoo-r1
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Date Submitted:             03-11-2006 21:25 CET
Last Modified:              03-15-2006 11:59 CET
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Summary:                    playing 2-channel sound on surround device uses rear
speakers
Description: 
If I play regular 2-channel stereo sound specifying device "surround51" or
"surround40" (or either of those with a "plug:" prefix) the sound is
output on the rear speakers.  6-channel playback is correct.
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 mru - 03-14-06 23:53 
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Yes, 6-channel playback is fine, as is 2-channel on the "default" device.
I installed alsa-lib 1.0.11-rc3; no change.

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 tiwai - 03-15-06 11:59 
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I understand slowly what's going on there.

The 4.0/5.1 surround outputs use the second DAC.  The behavior of this DAC
is somewhat strange.  If only 2-channel is used, it's routed to rear.  If
4 or more channels are used, it works as 4.0/5.1.

And, in surround40 and surround51 definitions, there is no restriction of
channels.  That is, if the PCM is opened with 2 channels, it is regarded
as the rear output.

Maybe we need a route plugin wrapping surround40/51 to fix the channel
numbers...

Issue History
Date Modified  Username       Field                    Change              
======================================================================
03-11-06 21:25 mru            New Issue                                    
03-11-06 21:25 mru            Distribution              => Gentoo          
03-11-06 21:25 mru            Kernel Version            => 2.6.15-gentoo-r1
03-14-06 15:04 tiwai          Note Added: 0008477                          
03-14-06 15:15 mru            Note Added: 0008478                          
03-14-06 15:22 tiwai          Note Added: 0008481                          
03-14-06 23:53 mru            Note Added: 0008524                          
03-15-06 11:59 tiwai          Note Added: 0008536                          
======================================================================




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