[mythtv-users] how to tell if 5.1 audio channels mapped correctly?

Jean-Yves Avenard jyavenard at gmail.com
Thu Nov 4 20:31:40 UTC 2010


On 5 November 2010 02:57, Dan Christensen <jdc at uwo.ca> wrote:
> [System details at end.]
> When I run ALSA's speaker-test program (speaker-test -twav -c6), it gets
> left rear & front center reversed; and also right rear & LFE reversed.
> But this discussion
>  http://www.spinics.net/lists/alsa-devel/msg26034.html
> suggests it's a known problem.  I found a test video at
>  http://www.tfm.ro/ac3/download/test_ac3.rar
> It plays with the correct channels in myth, but with the channels
> incorrect with mplayer, xine and vlc.

That's surprising ...
That it's wrong is one thing, but I would expect it to be wrong everywhere

Like if your incorrectly wired the speakers to the amp, it could explain it.

ALSA uses their own channel order.
AC3 / DTS uses another.

But this should be transparent to you
> However, other test clips I found play incorrectly in both mythtv
> and mplayer (and they are incorrect in different ways).  This
> includes a remixing of the above video.
> How can I be sure when watching a movie that I'll get the channels
> mapped correctly?  Isn't there a standard for this kind of thing?
> Am I just trying poorly encoded clips?

That's a possibility

I have some test clip there you can try:

> Any suggestions for how to fix my set-up would be appreciated.
> I'd also be interested in people letting my know whether the
> clip I linked to above plays correctly for them, and whether there
> are other test clips I should try that are known to be encoded
> properly.  (The test clips need to make it clear which channel
> is which.)
> Thanks,
> Dan
> I'm running myth 0.23 on a Gigabyte GA-E7AUM-DS2H motherboard.  It has
> onboard nVidia audio which uses the HDA Intel kernel driver.  I'm
> running Debian kernel 2.6.32-5-686-bigmem and ALSA userspace
> 1.0.23+dfsg-1.  I've got sound going out on the hdmi cable to my Pioneer
> VSX-820-K receiver, which has 5 speakers connected (no subwoofer).

This is the motherboard on which I test all the audio with myth..

So if there's one board I'm sure everything is working as it should;
it's this one ...

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