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Dolby Pro Logic IIx explained?

post #1 of 56
1/14/11 at 4:35pm
Thread Starter 
Hi Guys,

I'm struggling to completely understand the different formats.

I have a Sony STR-DG910 amp & have just upgraded my speakers & added an extra two so I can have 7.1.

Now what I want to know is if say I'm watching a DVD with 5.1DD & I select the Dolby Pro Logic IIx option on my amp will it still be 5.1 descrete channels with the Dolby Pro Logic IIx just matrixing the two back surrounds?
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post #2 of 56
1/14/11 at 7:34pm
Yes.
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post #3 of 56
1/15/11 at 10:30am
Quote:
Originally Posted by reggieroo View Post

Now what I want to know is if say I'm watching a DVD with 5.1DD & I select the Dolby Pro Logic IIx option on my amp will it still be 5.1 descrete channels with the Dolby Pro Logic IIx just matrixing the two back surrounds?

It will for PLIIx Music mode. But PLIIx Movie mode has an additional step, where the surround-back information is cancelled from the side speakers. So, 2 discrete surround channels go in, 4 matrix derived surround channels come out.
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post #4 of 56
1/15/11 at 10:41am
AFAIK, PLIIx-Music simply duplicates the sides to the rears, so there's no matrixing at all.
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post #5 of 56
1/15/11 at 11:56am
Quote:
Originally Posted by rdgrimes View Post

AFAIK, PLIIx-Music simply duplicates the sides to the rears, so there's no matrixing at all.

The surround-back information is matrix derived and different from the surround info; no duplication.
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post #6 of 56
1/15/11 at 12:00pm
okay now I am confused.....

so 7.1 ch is void to 5.1ch when pro logic movie is enabled?

what do you need to do to get all 7.1 channels to work?
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post #7 of 56
1/15/11 at 12:53pm
Quote:
Originally Posted by sdurani View Post

The surround-back information is matrix derived and different from the surround info; no duplication.

That would be true for PLIIx-Movie, but not for PLIIx-Music.
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post #8 of 56
1/15/11 at 12:55pm
Quote:
Originally Posted by soberparty View Post

okay now I am confused.....

so 7.1 ch is void to 5.1ch when pro logic movie is enabled?

what do you need to do to get all 7.1 channels to work?

You had it right the first time. If you want to make 7.1 out of 5.1, PLIIx-Movie is the way to go. PLIIx mode will not engage when the source material is more than 5.1.
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post #9 of 56
1/15/11 at 1:04pm
Thanks rdgrimes.....

thats the only setting I listen to anyway, I just wanted to clear my head on the thread. Thanks again!
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post #10 of 56
1/15/11 at 1:14pm
Quote:
Originally Posted by rdgrimes View Post

That would be true for PLIIx-Movie, but not for PLIIx-Music.

Play a 5.1 source through PLIIx Music and you (or anyone) can demonstrate for themselves that the sides and rears get different signals. No need to take my word for it.
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post #11 of 56
1/15/11 at 1:54pm
Quote:
Originally Posted by rdgrimes View Post

AFAIK, PLIIx-Music simply duplicates the sides to the rears, so there's no matrixing at all.

Quote:
Originally Posted by rdgrimes View Post

That would be true for PLIIx-Movie, but not for PLIIx-Music.

Maybe I can clear up the PLIIx modes, since I created them. Core operation of Movie and Music modes is identical. The Ls/Rs of the 5.1 source are processed into 4 new surround outputs. The only difference is that the Music mode offers a kind of "Center Width" control, so that when Ls and Rs carry the same (mono) signals, the decoder can map that signal across all 4 outputs rather than steering only to the rear speakers. This is very useful for movies with mono surrounds (i.e., Out of Africa), or just highly correlated surrounds, and of course for music mixes where hard steering can detract from the spaciousness of the mix.

If you are familiar with regular PLII when decoding 2-ch sources, the Center Width control allows the decoded center signal to be output from only the center speaker (CW=min) or only from L/R (CW=max) or several steps in between using all three speakers. PLIIx is using that same kind of control for the Music mode, but it is just internally preset somewhere in the middle.
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post #12 of 56
1/15/11 at 5:38pm
Quote:
Originally Posted by sdurani View Post

Play a 5.1 source through PLIIx Music and you (or anyone) can demonstrate for themselves that the sides and rears get different signals. No need to take my word for it.

I was going to take your word for it until Roger posted. Now I don't have to, but honestly I was all set to take it (after you wrote "or anyone" so I felt included), go down to the Two Jims, do your practical test, then come back and slap rd around with the power of personal testimony. Next time for sure.
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post #13 of 56
1/15/11 at 8:43pm
In case anyone isn't thoroughly confused yet, read this:

http://www.dolby.com/consumer/unders...x-details.html
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post #14 of 56
1/15/11 at 10:04pm
Quote:
Originally Posted by rdgrimes View Post

In case anyone isn't thoroughly confused yet, read this:

http://www.dolby.com/consumer/unders...x-details.html

If you find anything in particular there confusing, I'm happy to help resolve it.
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post #15 of 56
1/17/11 at 7:18am
Thread Starter 
Quote:
Originally Posted by Roger Dressler View Post

If you find anything in particular there confusing, I'm happy to help resolve it.

http://www.dolby.com/consumer/unders...x-details.html

It doesn't actually say if any channels stay as discrete channels. I had already read that info on the Dolby site & didn't get the answer to my question, that's the reason I came on here to ask.
So it's best to leave my setting to PLIIx all the time to make full use of my 7.1 speakers?
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post #16 of 56
1/17/11 at 8:05am
Quote:
Originally Posted by reggieroo View Post

So it's best to leave my setting to PLIIx all the time to make full use of my 7.1 speakers?

That's what I do, although many 2-ch tracks don't matrix well to 7.1 so often I use straight mode for stereo tracks. I use PLIIx-Movie for everything else and don't care for the sound of Music or Game mode.
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post #17 of 56
1/17/11 at 10:15am
Quote:
Originally Posted by reggieroo View Post

It doesn't actually say if any channels stay as discrete channels.

When processing 5.1 material, the three front channels stay discrete. The two surround channels are matrixed into four surround outputs.
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post #18 of 56
1/17/11 at 3:06pm
Just as a thoughtful aside, more purpose and dedication goes into the matrixing process than some engineers put into the actual recording.

Personally, I find it amazing that Roger Dressler, Jim Fosgate and others have the genius to take something and make it more life like and real, whether from two channel, four channel, or five channel sources. This has been a long, evolutionary process that didn't always work convincingly. It's convincing now, and it just keeps getting better.

I still love two channel sound. My most expensive gear is two-channel, and it sounds spectacular, but my less expensive (though not cheap) surround systems sound more real in the long run, even when running PLIIx from stereo.

Honestly, I do not care what's discrete and what's matrixed. I care about how it sounds in the room and where it takes me outside the room. PLIIx does a smash up job, especially after two skilled guys stop over and tweak it. (Thanks guys, you know who you are.) PLIIx is excellent, and I've already bought two spare speakers for a couple of my systems in anticipation of the full PLIIz rollout.

So Roger, if you read this, thanks for the work and well done.
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post #19 of 56
1/17/11 at 3:18pm
Roger,

I just joined the 7.1 world and all the options are daunting. My setup utilizes front-height speakers. So in PLIIz-height, how are the front-height channels derived? are any of the original 5.1 channels modified?

Thanks in advance.
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post #20 of 56
1/17/11 at 5:00pm
Quote:
Originally Posted by filecat13 View Post

So Roger, if you read this, thanks for the work and well done.

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post #21 of 56
1/17/11 at 5:17pm
Quote:
Originally Posted by jberq View Post

I just joined the 7.1 world and all the options are daunting.

Welcome into the 7.1 pool. Water's nice, eh?

All this daunting stuff can also be the source of some fun explorations into your music collection and personal preferences.

Quote:


My setup utilizes front-height speakers. So in PLIIz-height, how are the front-height channels derived?

I cannot discuss that until Dolby publishes public information on that. You know how it is...

Quote:


are any of the original 5.1 channels modified?

While I do not have latest information, based on experience, I'd say the original L/C/R channels are not modified, same as with current PLIIx.
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post #22 of 56
1/18/11 at 4:10am
Thread Starter 
Well Thanks everyone for your input & has pretty much cleared that up for me with regards to how the channels work etc.

I do have a few more questions though regarding 7.1 & PLIIx while watching Blu-ray.

When using my PS3 I used to switch between Bitstream & Liner PCM in the settings as I have read that I should switch between the two for Blu-ray & DVD. If I leave it on Linear PCM by accident while watching DVD I can't use the PLIIx setting on my amp, it just says not used so I have to make sure it's set to bitstream.

So for ages now I've used Linear PCM while watching Blu-ray & Bitstream for watching DVD. Now that I have 7.1 set up I obviously want to try & use all 7.1 but hit a problem when watching Blu-ray. I put on Avatar & switched my settings on the PS3 to Linear PCM & I can't use the PLIIx setting on my amp to have 7.1. it stays on 5.1. So I had a little mess about & switched the PS3 back over to Bitstream & got the usual warning come up before I hit ok "if you select bitstream, some of the audio from the BD may not be played" I hit ok & resumed the movie. The movie came on with no sound so I guess the warning was correct. I then went into audio settings on the blu-ray & changed it over from Dolby digital 5.1/DTS master audio to Dolby surround & I had sound again. All 7.1 speakers were working but my blue light indicating multi channel decoding on the amp wasn't lit up indicating I didn't have DD but across the front of my amp it said DD 2.0.

So If you can follow all that little lot can somebody clear up, is it worth having it in bitstream to watch Blu-ray & having audio set to Dolby surround to have 7.1 or will I get a much better sound having it in linear PCM & having DD 5.1?
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post #23 of 56
1/20/11 at 9:30am
If I'm understanding correctly, PLIIx Movie should be used for all 5.1 encoding movies, INCLUDING CONCERTS? I have been switching to PLIIx Music for my Bluray concerts. However, it seems that PLIIxMusic is meant specifically for 2.0 channel recordings? Is this correct?

So the decision of one or the other is based not on the genre being "music", but the recording being 2.0.

One other question / topic . I want to experiment with height channels. I have all the hardware in place. However, my processor will make me give up the rear surrounds. Instead of giving them up, I was going to just put a splitter on the side surrounds and send the signal to the rears as well. This will free up the processor to give me heights. Potential pitfalls I can see are delay settings. Any comments on this approach?
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post #24 of 56
1/20/11 at 10:52am
Quote:
Originally Posted by tony123 View Post

If I'm understanding correctly, PLIIx Movie should be used for all 5.1 encoding movies, INCLUDING CONCERTS? I have been switching to PLIIx Music for my Bluray concerts.

As I stated earlier, I do not like the Music mode for anything. I use Movie mode for 5.1 music too and like it a lot. Music mode does not sound natural.
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post #25 of 56
1/20/11 at 11:01am
By "should be used", I should have said "designed use". But I get your point.

I spent the last hour configuring in my height channels and "splitting" the surround to sides and rears. With only a few clips watched, I can't determine if I hear any difference at all.
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post #26 of 56
1/20/11 at 12:07pm
Quote:
Originally Posted by tony123 View Post

If I'm understanding correctly, PLIIx Movie should be used for all 5.1 encoding movies, INCLUDING CONCERTS? I have been switching to PLIIx Music for my Bluray concerts. However, it seems that PLIIxMusic is meant specifically for 2.0 channel recordings? Is this correct?

So the decision of one or the other is based not on the genre being "music", but the recording being 2.0.

You can use Movie or Music mode for any genre of content, in either 2 or 5.1-channels. Most newer movies work best with Movie mode. But there are examples of movies in 2.0 or 5.1 that work better with Music mode. These tend to be cases where the stereo is essentially mono, or the surrounds are either mono or highly correlated, and in a 7.1 system that would cause all the surround audio to come from the rear speakers only. It is usually nicer to have all 4 surrounds involved, and 5.1 Music mode does that.

Quote:


One other question / topic . I want to experiment with height channels. I have all the hardware in place. However, my processor will make me give up the rear surrounds. Instead of giving them up, I was going to just put a splitter on the side surrounds and send the signal to the rears as well. This will free up the processor to give me heights. Potential pitfalls I can see are delay settings. Any comments on this approach?

The main problem you will encounter is not because you cannot time align the 4 surrounds to your listening position, but rather that you might not be able to time mis-align them sufficiently to avoid a dense comb filter effect. Depending on the speaker geometry, it might sound just fine to split the surrounds. If you rock fore/aft in your seat, while some wideband surround sound is present like rain or applause, and you detect an obvious comb filter effect--a strong shift in timber, it might prove annoying over time. Otherwise, you're good to go.
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post #27 of 56
1/20/11 at 12:48pm
Thanks for the comments Roger! That's good news. I haven't noticed any comb filtering. My sides are dipole, and my rears are direct. They're all between 8 and 11' from the LP.

I am noticing that the efficiency differences in the two are giving me more volume difference than I would like.

I'll use it this way for at least several movies before forming an opinion on the configuration. So for now, it's 9.2 in PLIIz mode!
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post #28 of 56
1/20/11 at 12:48pm
Roger,

You wrote about DPL IIz:
Quote:
Originally Posted by Roger Dressler View Post

I cannot discuss that until Dolby publishes public information on that. You know how it is...

I thought I might find the information here but that just lists the formulae for Dolby Surround, Pro Logic and Pro Logic II, not even IIx (though I assume that's still very analogous, all in a 2D plane) so let alone IIz.

Would I be far off if I guessed it involves something like a 'Torso-Related Transfer Function' i.e. like a HRTF but much more sophisticated to model 3D reflections off the body?

Of course, I you can't disclose anything, I understand.
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post #29 of 56
1/20/11 at 2:50pm
Quote:
Originally Posted by T7T View Post
Would I be far off if I guessed it involves something like a 'Torso-Related Transfer Function' i.e. like a HRTF but much more sophisticated to model 3D reflections off the body?d.
Since the height speaker signals are intended to come from actual speakers displaced above the others, there is no need for any sort of HRTF processing.
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post #30 of 56
1/21/11 at 3:08am
Ok, thanks. I think I get it: That's what you would need if you wanted to simulate the height channels for reproduction through for instance headphones. Interesting.

Still intriguing to think how IIz might derive height cues from the audio signal.
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