AAC to AC3 on Win 7

In most home theater setups you connect your computer to your receiver via an optical cable and take advantage of S/PDIF to pass-through the original sound channels without your computer decoding them. This lets your home receiver directly get the Dolby Digital or DTS channels and send it off to your 5.1 surround speakers. This is great for AC3 (Dolby Digital) and DTS that you find on a DVD.

But newer digital formats are starting to use AAC for their sound encoding, because it's higher quality than AC3. Most receivers don't support this, and you only get stereo, regardless of having "3F2R/LFE" (5.1 channels) 

The answer is to do on-the-fly encoding of AAC to AC3. With Windows 7, this takes a little doing. Someone though, has already figured it out (it took me hours just to track this down)

  • Install Shark's Windows 7 Codec Pack
  • Run it's "Settings Application" as an Administrator
  • At the bottom, click the 'Reset All button"
  • Then click the Shark007 suggested settings
  • At the top, go to the MPG~MP$ tab and select 'Use Haali's splitter" (otherwise win media player crashes)
  • At the top, go to Audio and under FFDshow S/PDIF paqss-through, select 'use pass-through' 
  • At the top, go to the config section and click the FFDshow Audio config button
  • Select the 'output' section on the left, and 
    • enable Pass-through for the Dolby standards your receiver supports
    • enable ac3 output and only 5.1 streams
    • set 'Connect to:' to DirectSound
    • check 'Apply only to A/PDIF'
    • check 'Allow direct-to-file output'