How to filter out surround data

[kenma]

Hello,

there is a stereo-wav with surround data.

Is it possible to filter out the surround data from this stereo wav to get a dolby digital 2.1 (not only 2.0) file ?

[ultimatebilly]

I don't think this is necessary (and don't know how it can be done, but I'm sure it is possible).
A stereo with surround information contains 4 channels, which are matrixed into the two stereo channels.
So if you create a 2.0 AC3 from it, and decode it with an appropriate decoder, then it will recognize the surround information and will recreate it...
What you want to do is to add a subwoofer to a 2.0 track, but a wave with surround information doesn't contain a subwoofer, only left, right, (phantom) center and (phantom) surround...
There is no need for a subwoofer, since all sophisticated decoding circuitry will automatically root lower frequencies to speakers that can handle them -> the subwoofer(s).

[kenma]

but why is the software showing an encoding-template named as

2/1 (L, R, Ls) and Ls means Left-Surround

[ultimatebilly]

Well, then I was wrong with the subwoofer in this case, but nonetheless...
I guess the template is for cases where you don't have a wav-file with surround information as a source, but 3 separate discrete channels, being L,R and LS.
So it seems that for 2.1 the 0.1 is not the subwoofer as in 5.1, but the surround channel...
The information matrixed into the 2 channels isn't lost when you encode to ac3, so the receiver should recognize it...

But maybe I'm wrong? Could maybe somebody with some more knowledge in this field tell us how it is? :)

[kenma]

thanks anyway ultimatebilly!

To All of you audio-engineers, is it possible to filter out the surround signal from that stereo-wav and can I get 3 discrete channels (L, R, Surround) from one stereo-wav, if the source stereo-wav has surround-info. included ?