Multiple-speaker sound is intoxicating. In college, I spent an entire month spinning music around the conservatory's quadraphonic monitors. It was easy to set up: I played sounds into the first track of a four-track tape recorder, routed the output of that track (delayed by the distance between the record and playback heads) into the next track, and so on, with each track feeding a different speaker. With a percussive sound, the echo spiraled around the room, ringing out from each corner in turn. With sustained sounds, the swirling effect was amazing, particularly if I bent the pitch of the notes. It felt like floating down a sonic vortex.
But outside the ivory tower studios, the world was a stereo place. There was no easy, affordable, and popular way to distribute one's own multichannel music.
Enter DVDs. The players are so ubiquitous they practically come inside cereal boxes these days, and they all play 5.1-channel Dolby Digital (AC3) files. Most models play 5.1-channel DTS files too. So there was the playback mechanism, but how exactly does one go about making a surround-sound disc? The commercial encoding software costs about $995 and it seems that one would need a pile of hardware as well.
Inspired by the Zoom H2 surround recorder, with its four mics and $199 street price, I started playing with the files reviewer Mark Nelson was generating. With some experimentation and guidance from plugin developer Daniel Courville, I found an inexpensive way to burn surround sound onto DVD.
For efficiency, I'll discuss a Macintosh approach here, but the techniques are the same on Windows. If you're new to surround concepts, look at the last two pages of our H2 review, which offer background and numerous links to more detail and tools.
In short, you load six mono WAV files into an AC3 encoder and then drag the resulting file to your DVD-burning program. Depending on the encoder's capabilities, you may need to interleave the six mono files into a single multichannel file first. And in Roxio Toast, which we'll use here to burn the DVD, the secret is to Option-drag the AC3 file.
The battery-powered JVC SU-DH1 converts an optical AC3 or DTS signal to headphone surround. Hear it in action below.
The six WAV files will correspond to the speaker channels Left, Right, Center, Left Surround, Right Surround, and Low Frequency Effects — aka subwoofer (L, R, C, Ls, Rs, and LFE). For my first experiment, I started with four mono files derived from a dual-stereo thunderstorm recording Mark made with the Zoom H2. (In surround recording mode, the H2 produces two files: stereo front and stereo rear.) I used BIAS Peak to split each stereo file into two mono ones, and then converted the sample rate to the DVD-standard 48kHz.
Because I wasn't using a center channel and because DVD players can fill in the LFE channel if nothing's there, I made two dummy files by duplicating one of the mono files and silencing it with Peak's Silence command. To match a standard 5.1-speaker layout more closely (the H2 mics have a non-standard orientation), you can use one of the free plug-in processors mentioned in the H2 review: H2-Zoo (Win) or Zoom2Five (Mac).
I planned to use ffmpegX ($15) for AC3 encoding, so the next step was to convert the six WAVs to the interleaved single WAV ffmpegX requires. For that, I grabbed the free De-Interleaver. Daniel Courville recommended sorting the input files in L, R, C, LFE, Ls, Rs order, but I got better results with L, C, R, Ls, Rs, LFE. (You can re-order the files by dragging them up or down in the De-Interleaver window.)
The next step was to drag the resulting WAV file onto ffmpegX, select AC3 in the Target Format pane, and hit Encode. Moments later, I had a real AC3 file — for $980 less! Opening Toast Titanium 8, I selected the Music DVD format and Option-dragged the AC3 file onto the main pane. This is crucial: if you simply drag it, Toast will collapse it to stereo. Figure 1 shows the window after a proper drag.
Fig. 1: If you see this audio configuration in Toast, you have successfully imported the AC3 file. Failing to Option-drag the file will make it collapse to stereo.
After a quick trip through Toast's menus to change the disc titles, I rendered the output to a VIDEO_TS file, which I could play in Apple DVD Player. I connected my JVC SU-DH1 Dolby Headphone decoder to the Mac's optical output, set DVD Player's audio output to Digital Out, and the decoder's Dolby Digital LED lit up while sound swirled around my head. (Note that unless you specifically set the Mac's output to Digital Out, the optical signal just comes out in stereo.)
So you can hear the effect on the web, here's a recording of the surround piece run through the Dolby Headphone processor at four different settings: Off, Small, Medium, and Large. You can use normal headphones.
There's a lot left to explore. You can supposedly use AC3 files in iMovie and iDVD, but I haven't had success with that yet. Still, after cracking the DIY DVD surround sound code, I have the same "Wow! You're not supposed to be able to do this at home!" rush I got when I burned my first CD. Download my AC3 and VIDEO_TS example files (3.8MB zip file) and let us know what you start spinning.
With Minnetonka SurCode CD-DTS ($99; Win) or Immersive Media Research Vortex Surround Encoder ($50; Win/Mac), you can create 5.1-channel DTS files you can burn onto CD-R and play in most DVD players. To your computer, the DTS file looks like a standard stereo WAV or AIFF with a CD-compatible sample rate of 44.1kHz. (DVDs typically use 48kHz.) But if you listen directly to the encoded file, you'll hear a sound somewhere between white noise and static. You need to run it through a DTS decoder to expand the sound back into six channels.
In a home theater setup, the decoder is typically in the receiver. The DVD player feeds the DTS signal to receiver through an optical cable, and the receiver in turn feeds six speakers through its six analog speaker outputs. A simpler, more compact option is to use powered multimedia speakers that come with a decoder box, such as the Logitech Z 5500s or Creative Labs GigaWorks series.
You can also burn AC3 WAVs and AIFFs onto CD, but the encoded signal sounds much harsher than the DTS one, so be sure to label the disc so no one tries to play it in a normal CD player.
Here are two sites with DTS and AC3 WAV files to download and experiment with, along with more background on burning surround-sound CDs:
Mac OS 10.4 (Tiger) added a slick audio feature called USB audio aggregation. When you plug USB audio devices like speakers, mics, or audio interfaces into your Mac, you can address them as a single combined device. Using a stereo audio interface and a 4.1-channel multimedia speaker system I had lying around, here's how I used this feature to get true quadraphonic playback:
Fig. A: After clicking the "+" button to define a new aggregate audio device, you use the checkboxes to enable inputs and outputs. I named my new four-in/four-out device "4x4 Internal + Edirol."
Fig. B: Clicking the Multichannel button lets you configure multiple speakers. My choices were Stereo and Quadraphonic.
To test my new speaker setup, I recorded a quick musical demo with KAE Labs VocalWriter, a singing synthesizer with a built-in multitrack sequencer. I set track 1 to sing "One," track 2 to sing "Two," and so on, and then exported each track as a mono AIFF file. Opening a new file in QuickTime Pro, I inserted the AIFFs into four discrete tracks. (To insert files into discrete tracks, you open the source files one at a time in another QuickTime player, Select All, copy, and then add them to the new file with the command "Add to Selection and Scale.")
Then in the QuickTime Properties window (Figure C), I mapped each track to a different speaker. Here's the result, along with a quadraphonic movie of Mark Nelson's thunderstorm recording, so you can check it out yourself. If you don't have four speakers connected, the output should collapse to stereo.
Fig. C: To map QuickTime audio tracks to specific speakers, press Command-J to open the Properties window, and then select the speaker you want from the pop-up menu.
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