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[pwantzel]

I just got 5.1 channel speakers for my HTPC (previously I had only 2 channel stereo speakers).  I'm having trouble getting it to work right.  But in a different way then other posts I could find.

If I have an audio source that is 2-channel mp3, or a video source that includes 2-channel mp3 sound, I want it to play using just the front speakers.  But I get sound out all speakers!  If I play a 6-channel .ac3 file that contains individual voice announcements "left front", "right front" etc, to test the setup, I get each channel from more than one speaker, but a different combination of speakers for each channel.  I get the same behavior in WMP with the .ac3 and .wma 6-channel files.

Something is obviously wrong.  But I don't know which part.  If I play the 6-channel .ac3 file in VLC, it plays fine - each channel's announcement appears only on the correct channel.  I know that VLC doesn't use codecs like most other media players, that they are internal to it.  But this means (I think) that the audio hardware is working correctly, right?

This is on an older Dell Dimension E510 computer that has on-board sound via a SigmaTel chip.  The sound output is individual analog connections for 6 channels (actually 8, but I'm not  using the other two).  Windows XP MCE SP3.  MC 15.0.35.  I changed the audio settings to "5.1" of course but could find few other setup options for audio.  Nothing about "matrix" or "expand stereo to 5.1 channels".  My speakers (Logitech X540) have a "matrix" button, and when I press it, I get more and different sound out of the back speakers.  But normally I keep it unpressed.

Any ideas?

[Matt]

I would recommend setting Media Center's DSP Studio to 5.1 output always.  There is an option 'For stereo sources, only mix to 2.1' if you want it.

This should prevent the driver from doing any unwanted 2.0 to 5.1 mixing.

I would also enable Options > Video > Audio for Video, DVD, & Television > Playback device: Same as device used in audio playback.

This allows DSP Studio, ASIO, WASAPI, etc. for any video playback as well.

Let us know how you fare.

[pwantzel]

OK, not too good.  If I select "For stereo sources, only mix to 2.1" I get front-only for all files (2 and 6 channel) and if I don't select it I get all speakers for all files.  I've selected "5.1" for channels and "JRSS Surround Sound".  For Audio output mode I have "direct sound".  Is this right?  I've verified the audio type in each file with MediaInfo.

The better news is that the .ac3 6-channel test file does play correctly (each channel's information to only the correct speaker).

[JimH]

This might be useful:
http://wiki.jrmediacenter.com/index.php/Surround_Sound

[Matt]

OK, not too good.  If I select "For stereo sources, only mix to 2.1" I get front-only for all files (2 and 6 channel) and if I don't select it I get all speakers for all files.

Are you sure you're really playing a 6 channel file?  It sounds to me like whatever decoder you're using is really only providing Media Center 2 channels.

It sounds like if that gets squared away, everything else is working.

[pwantzel]

I've read the "surround sound" page.  It looks to me like this applies only to digital output to a receiver that does the decoding.

I'm sure that MediaInfo states that the video file contains 6-channel AC3 audio.  And h.264 video in a .mkv file.  How can I be more sure?  How can I determine what "whatever decoder you're using" is?  Or how do I specify/acquire one?  I do have PowerDVD installed, which is supposed to allow 5.1 playback from DVDs.  Does this provide a decoder for use by non-DVDs?

Remember that I stated I could play a 6-channel .ac3 audio file just fine.  On further investigation, it appears that VLC opens to play that.  How/why does this happen?  What is set to cause this?

[Matt]

I'm sure that MediaInfo states that the video file contains 6-channel AC3 audio.  And h.264 video in a .mkv file.  How can I be more sure?  How can I determine what "whatever decoder you're using" is?  Or how do I specify/acquire one?  I do have PowerDVD installed, which is supposed to allow 5.1 playback from DVDs.  Does this provide a decoder for use by non-DVDs?

Remember that I stated I could play a 6-channel .ac3 audio file just fine.  On further investigation, it appears that VLC opens to play that.  How/why does this happen?  What is set to cause this?

While playing the video, right click on the display, pick 'DirectShow Filters' and click the audio decoder you're using.

If it's FFDShow, you need to uncheck the 'Mixer' option in the tree.  I believe its default is to use 'Mixer' to convert to 2.0 output.

[pwantzel]

It was ffdshow, and mixer was selected, and deselecting it seems to have fixed the problem.  I'll try it on a few more files, but it looks OK.

Thank you very much.