How To: Realtime AC3 / Dolby Digital Encoding for Games

This simple how perhaps might be useful to those who are connecting their sound card to a receiver that doesn’t have analog input (like me for example) and using the Matrix Decoder on your receiver doesn’t sounds as good as using a Dolby Digital / AC3 encoded files. So what this simple how to trying to achieve is to do a realtime AC3 Encoding using software (in other word, using your CPU power to perform realtime Dolby Digital encoding) and then deliver that Dolby Digital / AC3 encoded material to your receiver. Although unfortunately it doesn’t come for free

Before i begin, please note that this tips is intended for use in Gaming only (or perhaps listening through your MP3/MP4s collection if you’re not using a music player that support realtime Dolby Digital Encoding from a plugin, like Winamp for example). Because for movie and music listening purpose the process is much simpler plus there’s no latency problem like this and you don’t need to spend money (unless you want to donate for the project) .. but i’m not going to describe the process for movie and music listening purpose here because as the title says this is for games :)

If you’re currently using below setup, then chances are you don’t need to spend $30 USD to get a realtime AC3 Encoder / Dolby Digital Encoder. But i haven’t tested it yet because i don’t have the required hardware

  • If your sound card belong to the Creative Audigy Series

    Then you can try using redocneXk combined with Creative ASIO Driver or KX Driver. As the documentation itself can be found here
  • If you have the new Creative X-Fi Series (a much better option for X-Fi series)

    Then you can spend $4.72 USD, and get the Dolby Digital Live and DTS Connect Pack from Creative Store

Otherwise, if your setup doesn’t match above configuration then unfortunately you’ll need to spend $30 USD for a software that is required for this purpose BUT if you don’t mind on spending more money and prefer to skip all this together, you can just buy Diamond Multimedia Xtreme Sound 7.1 DDL (equipped with Dolby Digital Live feature, which is unfortunately not available on where i live because there are no distributor for it here according to the official website) if you prefer a cheaper alternative to X-Fi (at least for me)

Anyway here are the steps:

Required Software

  1. Virtual Audio Cable ($30 USD): Link

    Trial version available with some limitation like female voice reminder each several seconds

  2. AC3Filter (freeware and open source): Link
  3. GraphStudio (freeware and open source): Link

Let’s begin

  1. Install VAC (Virtual Audio Cable) and AC3Filter (GraphStudio don’t need to be installed, you can place it anywhere you like)
  2. Run VAC Control Panel from Start Menu and make it look like this

    Virtual Audio Cable Control Panel

    You’re free to adjust the sample rate and also bps. As for the Number of channels, read the special note at the bottom

  3. Now run AC3Filter Config from Start Menu and make it look like below

    AC3Filter Configuration - Main Tab

    If your source sample rate isn’t 48000 you need to set the Output Format rate to 48000 (i already configured it to always deliver 48000Hz so i don’t need to set it in AC3Filter) or you can just set the AC3Filter sample rate to 48000

    AC3Filter Configuration - Main Tab

    Note: You should adjust the bass redirection frequency according to your Sub Woofer capability as described in the manual and feel free to adjust everything on this section to your liking

    AC3Filter Configuration - SPDIF Tab
  4. Now make sure that Virtual Cable is configured as default Playback Device in Windows ( open Windows Control Panel and then choose sound )
  5. And then run GraphStudio and then choose to add new filter (you can press CTRL+F for shortcut) and add:

    1. Virtual Cable 1 from WDM Streaming Rendering Device because it provides much better latency instead of the normal Virtual Cable Line that needs to be adjusted everytime before you connect it to AC3Filter
    2. AC3Filter from DirectShow Filters to upmix the stereo channel into 5.1 AC3 / Dolby Digital
    3. DirectSound: [ Your Sound Card Name Digital Output ] from Audio Renderers. Where your sound card name is your physical Sound Card Name (mine is Realtek Digital Output)
  6. Finally connect each filter so it’ll look like below image for an example ( Virtual Cable 1 ADC ’ AC3Filter ’ DirectSound: [ Your Sound Card Name ] )

    GraphStudio
  7. Now to make things easier for future access, you should save the graph you’ve created in GraphStudio so you can just load your graph in the future for easy access
  8. Now click the Play button on GraphStudio … and see whether the Dolby Digital indicator on your receiver is activated. If you can see Dolby Digital indicator on your receiver that mean everything is done. So try playing one of your game to test it

But please keep this in mind, in order to use this realtime ac3 encoding in the future, you’ll always need to launch GraphStudio first and then choose the play button on GraphStudio, or else it’s not going to work

Credits goes to the poster at AC3Filter Forum because without his post, i would have to get a X-Fi card which is … well … i’m not sure on when i can get it :)

Special Note

As a side note, upmixing like this may result in lower sound quality (perhaps if you can notice it). Also there’ll be latency problem (noticeable). So for certain games (such as Pro Evolution Soccer 2011) i choose to disable realtime ac3 encoding. But for games like Assassin’s Creed Brotherhood and Need for Speed Shift 2 Unleashed, it sounds great to me :D

And to those who are wondering, on why i didn’t set the number of channel to 5.1 (6 Channel) in Virtual Audio Cable Control Panel and Virtual Audio Speakers Configuration in Windows Sound Control Panel under Playback Device and Recording Device. The reasons are:

  1. If i set the VAC Number of Channels to 6 in VAC Control Panel (and configure VAC Speakers Configuration under Windows Sound Playback Device to Stereo plus change the Windows Sound Recording Device for VAC to 6 channels). All the sound levels outputted are equal which means Front Left (FL), Front Right (FR), Front Center (FC), Back Left (BL), Back Right (BR), and Subwoofer (SW) at the same level (can be seen in AC3Filter) which is wrong (i think, but since i’m not audio professional, please ask your nearest audio professional). But if you prefer it that way you can just change the Recording Device in Windows Control Panel for your VAC device to 6 channels and keep the Playback Device for your VAC device to Stereo
  2. If i set VAC Number of Channels to 6 and change both Playback and Recording device under Windows Control Panel to 6 channels … i get an error message about DirectShow Problem (can’t create buffers, when tested using Winamp)

And because of that reason, i guess it’s better to upmix it from Stereo to 5.1 AC3 / Dolby Digital :)

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