How to get 5.1 surround sound from AAC file using spdif?

This is a tutorial to get 5.1 surround sound from your receiver (capable of handling AC3) from an AAC file. I tried hard to make this work and did lots of googling. Finally found success in doom9 forum.

Here we will be using Media Player Classic and ffdshow.

1. First install MPC and ffdshow.

2. Open ffdshow audio decoder and choose ffdshow to decode AAC (use libfaad2 for AAC in codecs page)

3. In the Resample page, tick the checkbox for Resample. Change "resample to" box to 48000 Hz. Make sure that "Resample always" radio button is checked.

4. In the Output page (under OSD), check AC3 (S/PDIF encode mode) under Supported output sample formats. Make sure the bitrate is 640. Check "Don't use WAVEFORMATEXTENSIBLE header when not needed".

That's it. Press Apply.

Now your AAC will be passed (resampled) to your receiver as AC3 and your receiver will identify it as Dolby Digital.

Note: All the audio going thru ffdshow will be resampled. If you are using MPC for Ac3/DTS, this will reduce quality. I suggest you to use inbuilt MPC AC3/DTS decoder (which can send signals directly to s/pdif) or AC3 filter.

How to force VLC to use S/PDIF.

After I got my receiver, I wanted to pass through AC3/DTS to my receiver, so that it can decode the signals digitally. In VLC I had to select that option every time I play a movie. To default this,

first go to Tools >> Preferences >> Audio, and then under "Output Module", select "Win32 waveOut extension output." You should now see a check box that says "Use S/PDIF when available." Tick it, click "Save" and you should be good to go.

The VideoLAN Forums • View topic - Help with a/52 over s/pdif

AC3filter Dolby AC3 passthrough

If you're sending AC3Filter's output to a surround sound equipped home theater receiver you only need to set the Output Format to AS IS (No Change) and PCM 16bit (for standard Dolby Digital or DTS) and check the Use SPDIF checkbox. This will bypass AC3Filter's internal processing and send the original signal through your S/PDIF connection.

More details here.