Friday, November 30, 2012

Composing for Surround Sound

My desktop computer, although bottom-of-the-line, came with six audio jacks on the back and two in front.  It can play surround sound.

$20 of mini-earphones from eBay and - see below - anyone can listen to surround sound. The possibilities for arranging music for surround seem seductive.

Here's what I've found so far...  

My desktop plays 8 channels at 32 bits definition, 192kbps - four stereo pairs. Most modern desktops apparently can do this.  I only needed to download and install a large set of codecs from CNet. These are supposed to work on XP as well as Windows 7, so the same package may work on your  machine. Here's the link:

1)  Download and install this set of codecs.  

It installed quickly for me. A reboot, and then, when I went to  "Control Panel / Sound / Playback / Speaker Properties / General" up pops a screen that shows four stereo outputs, as follows.

       L    R      Front panel (green)
     RL  RR      Rear panel (black)
     C    Sub    Rear panel (red)  (This is for the two monaural channels, "Center" and "Sub-bass.")
     SL   SR      Rear panel (blue)   (Not sure what the S stands for.) 

Cakewalk lists all four pairs of outputs, although it can only send to one stereo pair.

2)  Test your installation. Download this little .AC3 file.  It's an 8-channel audio file.  It sends audio through each channel, naming the channel as it goes. Play it with the Windows Media Player. You should hear each channel reporting in.

The .AC3 file is the filetype for surround sound files. AC3 files fulfill the "ATSC A/52" specification, a phrase which brings up a lot of data on google.
Both QuickTime and Windows Media Player can play the .AC3 file type.

3)  Audio output: 

   a) The interface choices.
      1)  eBay sells little USB stereo adapters for $3.19. They claim "5.1 support" but there appears to be only one stereo output. Four of these and a couple of USB splitters would give 8 physical channels of output for under $20.

      2) a full 8 channel 7.1 adapter costs $18.53.   (googled "usb audio adapters s/pdif")   This adaptor has 4 stereo output jacks.
  a)  Speakers: most computer stores - even our Office Depot - sell 5-speaker sets for 5.1 surround sound. To get the two extra channels for 7.1 sound, add a pair of powered speakers - old computer speakers, music studio monitors or even an old hifi with a couple of speakers. Then you will have 7.1 surround sound.

   b)  Headsets:  make your own surround sound headset for $8 - $23:

   c)  Headsets:  $75  buys a pair of 7.1 "surround sound" earphones.  $90 buys a wifi headset.

- - - - - -

How is a person to make the music?

Audio editors that can handle 8 channels of output cost $350 and up. Sound Forge and Adobe Audition are the best, and the Adobe has more features.  That's something for the future. Nice to know it's there.

For now, I can test out ideas by exporting 4 same-length stereo files from Cakewalk. They can fade from one to the other, moving music through the sound sphere.  FFmpeg can compress these files as a group into the AC3 format. There may be other tools that can do this, too. But I'll probably need to get Adobe Audition to do anything serious.

So that's what I've found. My headset (I ordered the wifi 7.1) will be showing up in a day or two. If you liked, you yourself could begin to play with the environment for $40 or less.

There are programs that convert ordinary stereo to 8-channel sound. I suspect that they split the incoming sound by frequency and give different acoustic effects to the different frequency ranges. But people like it. There is certainly nothing beyond 2 channels of information in stereo sound. Similarly truthful, there are cheap usb adapters on eBay that claim to provide "virtual 7.1" sound - that is to say, stereo. You can play artificially created surround sound through them and they produce stereo again.

Musical compositions that are intended directly for the surround sound environment may come as something new. With the technology in place in many homes but only used for games and re-processed stereo, even a so-so composer might be able to find a big market for his work.

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