Dolby Pro Logic II / IIx tidbit

[ssully]

This is something PLII/IIx fans should know ..it was news to me, so I thought I'd share.

I've been intrigued by,a nd using, DPLII processing for some years now on my two-channel sources. The nice people at Dolby Labs have been answering my email questions for a year or so now, helping me understand their product. One thing I'd noticed from reading the literature was that in Music mode, DPL II actually rolls off the high frequencies somewhat -- Dolby's justification is that in real life, ambient sounds are often rolled off due to room effects. However as we know, discrete surround music mixes, as found on DVD-A and SACD, don't do this. Nor does DPLII always merely generate 'ambience' in the surround channels -- sometimes the ;mix' can be quite 'active', depending on the characteristics of the 2-channel source. So I asked them if they'd consider making this filter user adjustable -- so users could turn it off or on.

here's what Dolby toold me in reply:

//
[Dolby] The shelf filter is -3 dB at 6 kHz, and -4 dB at 10 kHz. The
shelf limits at 4.7 dB. In the newer Pro Logic IIx code base, we
revised the Panorama mode such that when it is turned on, the rear
shelf filters are turned off. This accentuates the effect, but did so
without adding another switch. If a standard PLII decoder is made
from this newer code, the same operation will happen.

//


To me, this was interesting news! Panorama is 'off' by default in every DPLII home audio implementation I've seen. So, on my new-ish Pioneer receiver, which has DPLIIx, I turned Panorama *ON*, and there was an unmistakeable increase in surround activity . Tangerine Dream's 'Zeit' CD was rather amazing to hear this way.

Those of you who favor 'active' quad mixes, might want to give this a try, if you've previously been unimpressed with DPLII..

 

[JonUrban]

Cool! Thanks for sharing that!

 

[ssully]

I should add that Panaroma doesn't *only* turn the shelf filter on and off -- it also widens the soundstage, placing some instruments well to the side. So that of course is going to add significantly to the DPLII effect. That was its original function, in fact.
The filter toggle was added to the Panorama code for DPLIIx (and also to DPLII since then).

Unfortunately, Dolby doesn't seem to consider it necessary to have a separate toggle just for the shelf filter. Movie mode doesn't use the filter, but Movie mode employs 'autocentering' which always directs vocals to the center channel, whereas Music mode doesn't.

Anywah, the original (now a bit out of date, since it doesn't include changes since the introduction of DPLIIx)
white paper describing modes in DPL II is here.

 

[winopener]

Those of you who favor 'active' quad mixes, might want to give this a try, if you've previously been unimpressed with DPLII..

Where is present this "new code"? Hardware and or software examples to check out?

 

[ssully]

New code base is represented in any unit that has DPLIIx. And units that have DPLII, but were built since IIx was introduced . Is meaning, for example, pretty much any A/V receiver built in the last year or two. That's 'hardware'.

Is accepting any two-channel recording as input, producing some results more spectacular than others. That's 'software'.

Home THeater magazine is reporting this month that 'DPLII Surround Broadcasts Spread' and that 17 network TV series now have soundtracks in DPLII. I presume this means that shows are actually being mixed with DPL II playback in mind.

 

[BananaSlug]

I've noticed that ComCast digital cable now has an audio setup menu, and under advanced there are setting for compression level and the choice of 'stereo' or 'matrix'. Of course, I only noticed this as many channels are only playing in spanish the last day or two, have an extra description voice over, or are just the wrong audio for the program. Once they have it worked out it may be interesting to see how things decode. At present I notice that many shows don't sound/decode all that well, but when a comercial for a new big budget movie comes on there's suddenly sound all around me.

 

[BananaSlug]

A little bit of randomness is good

I guess I should edit my signature to specifically exclude ComCast...

 

[winopener]

New code base is represented in any unit that has DPLIIx. And units that have DPLII, but were built since IIx was introduced . Is meaning, for example, pretty much any A/V receiver built in the last year or two. That's 'hardware'.
Is accepting any two-channel recording as input, producing some results more spectacular than others. That's 'software'.

Maybe i need to clarify myself:
hardware: I've bought last july a dvd player that has a dpl2 decoding capabilities on it, how can i now it it is II or IIx? Need a scope to monitor the rear out?
software: cyberlink powerdvd and intervideo windvd provides dpl2 decoding by 3 years. from which version they do IIx and not II?