Kreshna Aryaguna Nurzaman wrote:
Anyway, while we're at it, does Dolby ProLogic IIx upmix discrete 4 channel to 5.1? See, Aureal 3D sound cards (as typical as sound cards during that era) has discrete 4.0 output, I wonder if DPL IIx can upmix them to 5.1 or 7.1, or even 9.2.
IIx can't do 9.1; that's IIz (II is 5.1, IIx is 6.1/7.1, and IIz is 9.1). Honestly though I don't like PLII (any of its variants) - it doesn't do a good job even with Dolby Surround content imho (I'd rather have "true" PL1). IME Pro Logic II (and IIx with 6.1) tends to "narrow" everything onto the center channel, and if the center channel is removed from the equation you just get faint matrix output on the various surround speakers and a chopped-up output on the main L/R. It very much strikes me as a "sound on all channels" feature to appease buyers who demand their 5.1 system plays everything in 5.1. Personally I'd rather see 4.0 stay 4.0 as well (I'm a fan of native reproduction). Having said all of that, there's some functional considerations that have to be taken into account:
- Most (I should say "practically all") receivers/preamps do not digitize their multi-channel analog inputs, which means they can't perform ANY processing on those inputs. In most cases you should still get channel leveling but that's it - no delays, no DSP (which is where Pro Logic II, or whatever else, comes from), no bass management, etc.
- Most receivers will, however, gladly turn 2.0 into 2.1 or 5.1 into 5.0 or what-have-you through their bass management features. It usually just depends on how you have the subwoofer output setup. Older Yamaha models (and perhaps other makers) take it a step further by offering a "SW/Both" mode where the internal processor treats the 5.0 (or 2.0 or 4.0 or whatever) speakers as if there is no subwoofer, so the main L/R get run full-range and take LF low-pass for any channels with bass management enabled, but the subwoofer also takes LF low-pass and the LFE (when present).
- Regarding the ".1", with the exception of pre-mixed 5.1 content (like a DVD), the ".1" channel really doesn't "exist" - its just a low-pass for a subwoofer (or subwoofers) to provide re-enforcement to the main speakers. So with 4.0 content, jumping it up to 4.1 is only needed if the 4 main speakers need the additional bass. With pre-mixed 5.1 content there's potentially "unique" data on that channel (because its mixed at the studio with six channels), so you either need the subwoofer, or a processor that will roll that channel into another speaker for output (iirc its a requirement for stand-alone Dolby/DTS decoders to support this, for example if you take your 5.1 receiver and set it to "Subwoofer: No" the LFE channel should be played on the main L/R; the "gotcha" is that afaik most stand-alone DVD players will just discard the LFE channel for their L/R analog outputs).
- What about ".2" (and .3, .4, etc)? With the exception of some very exotic Harman equipment, and some Yamaha models, there is no .2 or .3 or what-have-you. It's just multiple parallel outputs to connect multiple subwoofers without the use of splitters. Harman has some very high end equipment (sold thru JBL Synthesis and Mark Levinson, and a cut-down (and bugged) version for the HK990 receiver) that will actually EQ and manage independent subwoofer channels on the output side - it still takes 5.1 or 6.1 or whatever from the source media, but it treats each subwoofer output as a separate channel and sets leveling, EQ, etc accordingly. The idea being to "even out" response for very large rooms (which is where you'll usually see JBL Synthesis and Levinson theaters). Yamaha's older CinemaDSP models often had Subwoofer-L and Subwoofer-R outputs, which do things a bit differently from that - if they're just being "fed" LFE content from a valid 5.1 (or whatever) source they'll output it in parallel. But when bass management is enabled, the L subwoofer is dedicated for all of the "left" channel speakers, and the R subwoofer for all of the "right" channel speakers. Yamaha's newer CinemaDSP models, that also feature YPAO, will usually have the subwoofer outputs labeled "Front" and "Back" - if I remember right they're more or less parallel outputs with independent level controls.
So where this leaves A3D 4.0 (or 4.0 from an SB Live! or whatever) is that it needs to be digitized in some manner (to allow processing), either through a stand-alone external encoder, or with a *very* expensive preamp/receiver that can digitize multi-channel inputs (the only two that I know for sure to do this are the Accuphase VX-700 and Mark Levinson No502; I vaguely want to say the McIntosh MX-151 and Denon A1HDCI may also support it, and there's probably a "little brother" to the 502 that wears Lexicon or Synthesis branding that may do it as well). I know the VX-700 does support 4.0/4.1 -> 6.1 program, but I don't know if it's explicitly handled through Pro Logic II. The Levinson has more DSP features than it knows what to do with (and has the pricetag to boot!). I'm not sure if any of those models are still in production either.
As far as external encoders, you'd be looking at something like the Creative DTS-610: http://us.store.creative.com/B002651ZEM/M/B002651ZEM.htm (it isn't in production anymore, but you can probably find them used with some looking)
If you went with the external encoder you'd just feed the digital output into your existing decoder/receiver/preamp and go from there. I'm not sure what the DTS-610 would actually do with a quad input - you'd probably just get a dummy center channel (iirc the DTS specification doesn't actually allow for a 4.0 signal like AC-3 does).
I know you can usually find Dolby encoders (as in, actual Dolby Labs hardware designed for studios) on eBay - I do not, however, know if they would work for this feature. I've never played around with one, nor read much about them. 😊
Personally what I'd rather do with a 4.0 source, given that most soundcards with multi-channel output handle their own DSP and have mixer controls and so forth, is just feed that 4.0 signal into a multi-channel capable receiver/preamp and let it stay a 4.0 signal. Even if your receiver is setup for 5.1 or 7.1 output, and you take the 4.0 signal in, it'll just do a 1:1 and the un-needed speakers won't do anything. If bass management is a problem (e.g. the card won't output an LFE channel), you'll need some sort of external solution, like an active crossover or loudspeaker management system.
Some oddball "almost there" alternatives:
- A surround pre-amp from Parasound, the Halo P7 (http://www.parasound.com/halo/p7.php); it will take multi-channel analog inputs, and do bass management and leveling on them. It doesn't do any DSP though. I know McCormack Audio used to make, or perhaps still does make, a similar pre-amp as well.
- If you took a 2.0 signal, or could get a 2.0 Lt/Rt signal (ideally), you could feed that into a decoder/processor to accomplish whatever simulacrum you like (CinemaDSP, Pro Logic, Logic7, etc).
- In theory you could take the 4.0 output into a miniDSP (or gang of them) and perform processing on that, but it still leaves you with the preamp/control question (and it isn't a "neat" solution) - you wouldn't need as complicated as a pre-amp as the Parasound though, and could just dump the output into your conventional multi-channel input on a receiver.