mtrycrafts said:
7.1 is just a modification of 6.1 with 2 rear channels being mono.
Any current 7.1 systems are implemented that way. But there hasn't been any unified method to deliver a discreet set of 7.1 channels before HDMI. On a related (and not insignificant) topic, the DCI (Digital Cinema Initiative) spec allows for well past 8 discreet channels. As more theaters are built or retro-fitted as DCI-compliant, and more home theater systems have the capability for 7.1, movie producers/engineers will have the incentive to do their original audio mixes in 7.1 instead of the 5.1 or *maybe* 6.1 that they're doing now.
We now have the hope that HD-DVD and/or Blu-Ray content producers will start re-mixing and mastering the audio from catalog movies, but it's a better bet that we'll see new blockbusters in 7.1 starting with this summer's line-up.
There have been many experiments with 3-dimensional arrays and speaker systems with dozens of individual channels. Because of the shape of our ears, though, we can only do a great job of localizing height in the front hemisphere, especially if one removes the environment from the equation. Much of our rear localization comes from the timing of reflections off other objects near us.
The only reliable way to do true 360-degree localization is with binaural recording and headphones. I'll probably eat these words in 10 or 15 years, but I don't think we'll ever get past 10.2 channels/speakers in the most high-end of high-end HT systems. I believe it is more likely that engineers will play around with, and try to establish as standards, other virtualization techniques with 5.1 and 7.1 systems.