Configuring Surround over S/PDIF in FFDShow

Normally I'd put some sort of hypothetical story here, but I'm going to skip that and get straight to the good stuff.

This guide assumes the following:

• You're using the Combined Community Codec Pack, which includes FFDShow.  If you have some other setup using FFDShow, modify step 1 accordingly.  Also, I use Windows XP, so step 1 might change in the newer Windows OSes.
• You want a 5.1 surround setup.  If your sound card and sound system are both capable of more channels, modify step 5 accordingly.

Stuff you'll need:

• A computer
• A sound card capable of outputting S/PDIF
• A receiver with S/PDIF input, and of course an S/PDIF cable.
• Some form of entertainment with surround audio, for testing.  When in doubt, grab a DVD with 5.1 audio.
• A few minutes of spare time.

Now, without further ado, the instructions:

1. Go to Start->All Programs->Combined Community Codec Pack->Filters->FFDShow Audio Decoder Configuration
2. Click Output, all the way down at the bottom of the list on the left.  You may need to scroll to find it.
3. Check AC3 (S/PDIF encode mode).
4. Click Mixer, and check the checkbox next to it.
5. In the Output speakers configuration dropdown, choose 3/0/2 - 5 channels.
6. Check the LFE checkbox, the Expand stereo to center checkbox, and the Expand stereo to surround checkbox.  LFE will enable your subwoofer, and the other two are for compatibility with stereo audio streams.
7. Click LFE Crossover, and check the checkbox next to it.  Configure this page to suit your needs/tastes.  When in doubt, the defaults work.
8. Click Apply.

The actual setup process is done, but of course you want to test it, right?  Fire up Media Player Classic Homecinema and load something that you know has 5.1 audio.  If you aren't sure, right click in MPCHC and get the properties on it.  The Audio line on the Details tab should tell you, among other things, the number of sound channels.  Set your receiver to use the S/PDIF input, and start playing.  If you set everything up correctly, your receiver should show that it's getting a 5.1 Dolby Digital surround signal, and you should hear audio from the center and back speakers (and the subwoofer if it has low enough frequencies to trigger it).

Enjoy.