What is the the difference between 7.1 and below audio channel?

Answer 1

I'm not sure if I fully understand your question but I'll take a shot. Dolby 5.1 stereo has 5.1 audio channels: Right front, right rear, left front, left rear and center. The sixth one is what I like to call a "pseudo-channel". It is for a subwoofer. The reason it only counts as ".1" is because it only outputs limited frequencies. This is okay for a subwoofer channel because it's only purpose is to output extremely low frequencies. (e.g. All the "whole" channels output from 20-20,000Hz and the ".1" channel ouputs 20-120Hz) Standard stereo has two channels: left and right. Both output at full range of frequencies. There was a semi-popular audio system called "quad" back in the 70s and early 80s that was basically like Dolby 5.1 without the center and subwoofer channels. It had limited practical uses and was mainly broadcast over the airwaves because recording it required expensive recording and playback equipment. 7.1 or "Dolby Digital Plus" has, you guessed it, 7.1 channels. Im not sure what the extra 2 channels are for but I do know this is HD technology. It uses a lossless compression codec for full quality sound and can only be transmitted over HDMI or similar cables. There is a new format called Dolby TrueHD which has a max of 8 channels. This is even higher quality sound (lossless). Only a few Blu-ray movies are encoded with this at this point in time. Hope this helps!