divx + ac3 = digital output???

[Speed Racer]

I have several divx files encoded with ac3 5.1 sound. I have downloaded the codecs, drivers, nimo's pack and practically everything every dvix/ac3 guide tells me to. And yes, i can hear the movie and everything sounds great. I output my win2k computer thru the optical spdif output of my Fortissimo soundcard to my 5.1 surround sound receiver. I play the movies using PowerDVD and they work and play just fine.
However, I seem to be confused.
I'm under the impression that a divx encoded with ac3 sound will play like a DVD with 5.1 dolby digital surround sound. When I play a dvd with PowerDVD my digital light on my receiver lights up and then I know I'm outputting the dolby digital 5.1 surround sound. When I play the divx/ac3 movie though my digital light does not light up and it seems that it is only in stereo.
So my question is: Can you really get 5.1 dolby digital surround sound out of a divx file encoded with ac3? Or is all this hype about ac3 encoded files just to get the clearest STEREO sound without having to re-encode the ac3 to mp3/mp2/wav or whatever?

[crahak]

You absolutely can, and it's great. Most my rips have it (or AC3 2.0 at least) You need to have an AC3 filter installed, and have decoding of AC3 on your card disabled so your amp does it. It can be a pain to setup the first time, but it's well worth it

[The Maynard]

Good to know when I build my Divx system. Thanks!

[Gazorgan]

I have to move my rear speakers out...but it's worth it!

[Speed Racer]

crahak, thanks so much for your reply (and everyone elses)! Since i can hear the divx files I'm assuming I have the filter properly installed. So I guess my problem is that my card is decoding the ac3 instead of ouputting it (like a dvd would). Could you please explain how you disabled the ac3 decoding on your card so your amp can do it? I would litteraly buy the same soundcard you are using to get this divx/ac3/5.1surroundsound thing to work. I will also re-look at some of the guides for divx/ac3 now that you have enlightened me, thanks very much!

[Gazorgan]

You need the AC3 codec installed. You then need to tell your sound card to do 5.1 sound ( and configure your speakers that way ).

Now...to get it to a stereo, you need to re-config you soundcard. Most of the 5.1 cards have SPIDf output option, this is what you need to enable on your card (usually by losing you center/sub sound jack) and patch over to your stereo. It's a Cable and a Soundcard software setting for me.

[Speed Racer]

Gazorgan, please correct me if I'm mistaken, but when I play a divx file with ac3, I can hear the file. So I'm assuming that I have the codec installed. At one time I couldnt hear the file until I added some filters/codecs so that's why I assume I have them installed. I use the spdif optical output on my soundcard and also have the spdif enabled. It seems to me that my card is decoding the ac3 and then outputting it to the spdif instead of just outputting the ac3 without decoding it. Thus is the reason my receiver isnt seeing a "digital" output when i play the divx/ac3 files i believe. In this mode i can play dvd's though and get the "digital" output that's desired. That's my reasoning for me to believe that my card is decoding the ac3 and not outputting it digitally. I've had nitemares about this stuff lol!