AC3, 5.1, 7.1 audio....what's the different ??

[Ekin]

Ok maybe this was post before but can somebody tells me the difference and the quality of it ?? I know ac3 are the dvd audio compressed. I notice that some dvd have ac3 and after looking into them the ac3 file has only 2 channels. Others are 6ch. I use Soft Encode to encode my 2ch wav into 6ch ac3. When play in Apex and I did an audio selection it said 5.1...and I heard there's something about 7.1 So can somebody explain to me the difference.????:confused:

[Mystion]

The 7.1 protocol adds, two left and right channels to the current 5.1 configuration, thus having three front channels (L-C-R), two back channels (L-R), the subwoofer channel and two L-R channels allineated with the listener... Maybe you came along 7.2 as well, with two subwoofers... Looking forward to put a couple of speakers on my ceiling and pavement, when the appropriate protocol comes out... By the way why do you reencode a 2ch AC3 to 5.1 ???????? Is it that you don't like your movies look that good and sound even worse ?

[Ekin]

Ohh I don't know why I encode my ac3 into 5.1...Well to tell you the truth i don't know what i am doing here...Well ok...i have vob and i can demux them into wav. And by looking at that wav in Soft Encode..it tells me that I only have 2ch. and I looked at some other dvd's ac3. It have like 6ch. So I thought if i open my 2ch .wav file 4 times and assign the 6 speakers in Soft Encode...that would get me a better sound quality...??? is that true ?? well i know after encoding i get double the size as the origianl ac3 from the dvd...

[Mystion]

Well, actually sound quality has very little to do with whether it is played on 2 or 6 (or even 9 by now...) channels... I am not aware of the technicalities of reencoding a 2ch signal to 5.1, but I do not believe by any means you 'd get a real 5.1 output with channel separation and what you 'd expect from an acutal 5.1 stream... Why do you dcompress to .wav in the beggining (try BeSweet with the accompanying applications for the convertion instead...), 2ch AC3s are pretty low birate (192-224kbs) and excellent quality, so I 'd suggest you use them as they are... Try encoding to .aac or .ogg and see the results if intersted in lower bitrates and higher performance during playback... What you need to do is save space for video data, as in the end this makes most of the difference, having from the beggining a 5.1 AC3 is an entirely different story though...