5.1 Speakers won't work with Media Player Classic

Hi,
I have Windows 7 SP1 32bit and cannot get the center and two rear speakers of my 5.1 setup to work in Media Player Classic. I have the latest K-Lite Mega pack 10.40 installed
My Realtek onboard sound driver is up to date and all the 5.1 speakers work in Realtek test mode and all of them work correctly with Windows Media Player 12.
With both Audio and Video files only the Subwoofer and Front side speakers work. I have tried many different audio files [mp3, flac, aac] and video formats [mp4, mkv, wmv, avi]
and get the same result.
I found some information online where people had the same apparent problem and fixed it by enabling ac3 in the ffdshow audio decoder. This involved the following

Click "Options" and then scroll down to "Internal Filters." Ensure the "AC3" box has a checkmark. If the "AC3" box does not have a checkmark and surround sound still does not work, click "External Filters" on the left side of Media Player Classic. You are adding a filter to the media player. Click " Add Filter" and then click "AC3 Filter." Click "OK" to add the filter to Media Player Classic Home Cinema.

I have no entry in internal filters for Ac3 and when I follow the instructions to add the filter the only choice for AC3 is "AC3 Parser". Adding this makes no difference and I can still only get sound
in Media Player Classic from Subwoofer and front left and right speakers. The fact that all speakers work fine in WMP 12 means the speakers are wired correctly and working but WMP sucks for video
playback and I really want to use Media Player Classic.

***EDIT***** Have just discovered that certain mkv and avi files also give no output to centre and rear speakers even in WMP 12 too! All my MP4 and MPG MPEG videos work fine though.
This must be a codec issue therefore but I can't for the life of me work out problem*******

I would be very grateful if someone could let me know how to fix this issue.
Thanks in advance for any help


dandelion777

By default the decoder does not upmix the audio. That means that only front channels have sound when converting stereo to 5.1. All other channels are filled with silence.

Solution:
Codec Tweak Tool > Speakers > select "Same as input"

Then your Realtek driver will do all mixing.

Hi,
Thanks so much for such a quick response! This has also fixed my problems with AVI files in WMP12 as well as all formats in MPC

Never saw the "speakers" button hidden on right of codec tweak window. Previous installs of k-lite have always worked fine without
any speaker problems or tweaking, so I was totally unprepared for this.
Thanks again for your help

dandelion777

Same option can also be found in the installer.