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Thread: Surround Audio channels mixed up

  1. #1
    Join Date
    Sep 2005

    Surround Audio channels mixed up


    So I just installed the latest ubuntu 8.04 and did a surround sound test via speaker-test -D surround51 -c 6 -t wav

    All the speakers work except that the channels don't output to the correct channels (in windows all the channels work correctly so I know its not a jack thing)

    Heres the way that ubuntu is outputting to my channels
    front center is going to rear left
    rear right is going to front center
    rear left is going to subwoofer
    rear center (LFE) is going to rear right

    Front right and left are working correctly.

    when it does the test it outputs this:
    Time per period = 8.616492
    0 - Front Left
    4 - Center
    1 - Front Right
    3 - Rear Right
    2 - Rear Left
    5 - LFE

    Does anyone know how I can fix this so the channels output to the right speakers?


  2. #2
    Join Date
    Oct 2007

    Re: Surround Audio channels mixed up

    Brief version:
    It is all fine. it is a bug in speaker-test. Try switching your alsamixer to 6ch operation and play sound in gnome and notice that channels are mapped correctly after all

    Verbose Version:
    I had exactly the same problem this morrow.

    with me I noticed the following mapping :

    (signal goes) to (this speaker)
    Fleft to Fleft
    Fright to Fright

    Rleft to Center
    Rright to LFE

    Center to Rleft
    LFE to Rright

    So after looking at the mapping I noticed that I look very much like a jack issue.
    (as switching the 'center/lfe' and 'rearLeft/rearRight' jacks would solve the problem.

    After switching SpeakerTest worked fine and mapped correctly but I that this must be some wonky Alsa behavior as:
    1. evil proprietary Operating Systems
    2. the coloration of my jacks

    So as quick hack I switched the jacks.
    Yet as soon as I switched to gnome to test my 6ch setup in a real music environment I noticed that it was wrong again. Switching the jacks back set everything right again.

    Thus I assume that this is some bug on Speaker-test's side.

  3. #3
    Join Date
    Oct 2007

    Re: Surround Audio channels mixed up


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