AC3 without SPDIF

[paulo_andre]

I have a Sound Blaster Live! and the FPS 1600 and would like to hear 4.1 surround sound with my divx ac3 movies. Is that possible? If so, how?

[Rooster6975]

Not only possible, but easy!

I assume you mean 4.0 Dolby Surround and not Dolby Digital 5.1 because 4.1 does not exist.

If you have DivX with AC3 streams already included, all you have to do is install the AC3 filters. You can find them as part of the Nimo Codec pack available on this site.

http://www.divx-digest.com/software/nimo_pack.html

Then play your DivX in any player (I use MicroDVD) and the sound should be outputed to 2 discreet channels with the second set of channels encoded within the first. Your SB Live 5.1 card will be able to decode the 2 encoded channels into 4.0 Dolby Surround.

In fact, if you have AC3 DivX encoded with 5 channels, you can even get 5.1 Dolby Digital. Your SB Live card should be able to downmix it to Dolby Surround on the fly. You will end up with Left Right Center and one Surround channel. You should position your speakers accordingly.


Cheers,
Rooster

[beatomen]

well, I'm doing excactly as supposed, but there STILL no analog 6 channel output! The AC3 codec downmixes to 2 ch Dolby Surround (prologic), wich then is distributed to the 6 speakers (via the soundcards drivers), but that is NOT 5.1 surround - that is stereo extrapolated to prologic!

If the AC3-info is extracted from the file (with flaskMpeg) and then played back in Creative Playcenter2 there is REAL 6 channel surround - every channel i redirected to its respective speaker. But the AC3-codec used to decode AC3-data in DIVX files DOES NOT do this, which sux...

[Rooster6975]

You most certainly can get real 5.1 DD in DivX

The AC3 filter only downmixes to 2 channel Dolby Surround if that is what you tell it to do. If you extract the 5 channel AC3 sound from a DVD into a xxxxxxx.AC3 file, you will end up with a file with 5 discreet channels, and an additional LFE stream.

You can then mux that into your video for a 2 CD Divx Rip with AC3 5.1 sound.

What you have been doing is following guides to show you how you can get Dolby Surround 2 channel encoded sound, which as you point out, can be decoded by a Prologic decoder into 4 channel Dolby Surround. That is not 5.1. Download a utility called GSpot. It will tell you what type of audio you have on your divX. I am willing to bet yours will say AC3 192 Kb. That is 2 channel Dolby Surround. 5.1 DD will say AC3 384 or AC3 448.

Have a look at this guide :

http://www.divx-digest.com/articles/dvd2avi.html

When you use DVD2AVI to create a project file, it will strip the audio from the VOBs in the format you select. If you select AC3, you will end up with more than one AC3 file if your DVD had 5.1 audio. They are named xxxx2_0 or xxxxxx3_2. The first is a 2 channel Dolby Surround with 2 other encoded channels good for a Prologic decoder. The second file is the 5.1 file, it's name means 3 front channels plus 2 surround channels. Use that file with Gordian Knot when it asks you what type of audio you want to use with your video file. Remember that you have a large file now (likely 400 MBs), so you will need to make a 2CD rip.

At the end, you will have a perfect 5.1 DD divX backup of your DVD, and your amp will detect 5 discreet channels, plus the LFE. This is not theory, I have backed up all of my DVDs in this way. When I output them to my amp, the blue light comes on and the screen output reads "Dolby Digital 5.1". I can hear each discreet channel in my home theatre system.

Cheers,
Rooster.

[beatomen]

Actually I got it to work without doing much... Installed WinDVD 4 and *poof* I could select "6 channel (5.1)" output in the AC3-codec decoder settings in mediaplayer. This resultet in much rejoice and a splendid REAL surround experience )