[agathorn]

Can anyone out there really explain all this to me? I've been reading and reading for hours now and i'm even more confused than I started. My head feels like its going to explode.

There are audio encoding options when making Xvid files like AC3 which is huge and contains all channel data, then there is your standard stereo mp3 files which contain only 2 channels. Then I read about how you can compress AC3 to MP3 in such a way that the multichannel data is encoded, and can be decoded by a Dolby Pro Logic 2 capable receiver. Ok I think I get all that.

Then there are connections between the Xbox and the Receiver. You have your standard stereo RCA cables, and you have your digital optical connections.

Then in XBMC you seem to have the choice of Digital or Analog audio output.

I'm so confused, but what i'm really trying to find out is this:

Is it possible to have my Xbox hooked up to a Dolby Pro Logic 2 receiver with stereo cables, and encode my audio into mp3 using the aforementioned method that encodes the multiple channels into something DPL2 can decode, and then set it up somehow in xbmc so that the signal gets sent properly to my receiver where my receiver will decode the multichannel data and give me surround sound.

The reason i'm trying to figure this out now is i'm about to re-rip and encode ALL my DVDs because I recently found out I screwed them up and you can't seek through them. Unfortunately unless I buy new cables, which I don't want to spend the money on, I have only the stereo output cables, not optical.

My understanding of things is this is possible at least on some level, but not sure if its possible with XBMC.

Of course this may not even all make any sense to anyone, as it certainly has me confused. I need a dummies guide to this all!

[elupus]

short answare yes

you got it right, DPL(2) can get sort of surround sound out from 2 channel source, which is formatted in a special way.

normally when you downmix AC3 you do it to a format compatible with DPL.

[agathorn]

short answare yes

you got it right, DPL(2) can get sort of surround sound out from 2 channel source, which is formatted in a special way.

normally when you downmix AC3 you do it to a format compatible with DPL.

So does this just "work" in XMBC if I encode the audio properly, or do I need to set up anythign or turn on any settings other than DPL2 on my receiver?

[agathorn]

On a related note, what happens when the audio is encoded in ac3 directly and not downmixed?

[Gamester17]

AC3 and DTS that is not decoded/downmixes by XBMC (IE. digital pass-through output) is passed to your extenal reciever hardware without modification, your extenal reciever hardware will then do the decoding in its hardware. See:
http://xbmc.svn.sourceforge.net/viewvc/x...iew=markup

PS! Optical (S/PDIF) is always digital (so optical = digital).

[spiff]

it depends on the hw involved. but yes, if you passthrough it gamester is correct. it could also be decoded into 5 discrete pcm streams and outputted as double stereo (as some sound cards do, liek creative ones).
you gotta realize that ac3 is just an audio codec, like mp3 is one or aac.

[agathorn]

Yeah I understand AC3 is just an audio codec. But my question is in how that gets sent. Elupos indicated that if I have downmixed AC3 as a stereo MP3 file that it will get decoded by my DPL2 receiver, giving me surround sound. This is cool.

But if the file i'm playing has AC3, and i'm still using those same stereo jacks, will XBMC downmix that in a way that will then get decoded by my DPL2 receiver and give me surround sound as well? Or will XBMC do something quicker and cheaper and just give me stereo. that is what i'm thinking is happening.

Gamester cool diagaram but that seems to be for digital audio, as well as your explenation. but i'm connected through stereo jacks and so XBMC is set to analog audio.

[pike]

analog = PCM output if I recall correctly, see if that makes sense with the diagram

[spiff]

i'm not sure what the current alsa stuff does (linux) but on xbox the downmix is in hw and i believe it will carry the dpl info just fine. to put it (very) simplified, dpl is;

three channel stereo in front. extreme left is mapped to sl, extreme right is mapped to sr.

in any case, just get proper audio gear and passthrough if you want surround. dpl is just a hack and wont ever be on par with proper discrete channel streams

[agathorn]

in any case, just get proper audio gear and passthrough if you want surround. dpl is just a hack and wont ever be on par with proper discrete channel streams

Yeah my plan is to eventually get the right cables, but after buying the wrong ones not once but TWICE, i'm holding off a bit till I get some more money.

Due to the xbox being quite old, i've been having trouble finding the right cables. I found some used cables at GameStop which I quickly bought and brought home only to find they were component out which is what I needed, but only stereo audio.

Then I found a set on eBay real cheap that I snagged real quick without reading closely, and it turned out to be optical audio which I wanted but only s-video out :p

So I have two cables each with only half of what I need lol.

I guess what I will do right now is see about encoding everything with AC3 since I do plan on eventually getting the right cables. So they'll be future proofed.