Pro Logic II: Surround Sound from Stereo
Dolby Podcast Episode 11, March 29, 2007
Roger Dressler of Dolby Laboratories explains how to get surround sound from stereo content – music, movies, television or games – with Dolby Pro Logic II and how to use your AV receiver’s “movie”, “music” and “game” modes for the best sound. Plus, listener, Andre, asks how to best experience Dolby Digital EX in his home theater.
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Mentioned in this Episode
[intro music]
Jack Buser: Hello, and welcome to Dolbycast, the insiders guide to entertainment technology from the experts at Dolby Laboratories. I'm Jack Buser.
Craig Eggers: And I'm Craig Eggers.
Jack: And we're here to give you the straight talk on everything you need to please your ears.
Craig: Hey Jack, we're back.
Jack: That's right, another wonderful episode of Dolbycast.
Craig: You know we got a lot of great feedback on our last Dolbycastwith Jim Hilson [of Dolby Laboratories in Mixing Sports in 5.1-Channel Surround Sound on March 15, 2007 –Ed.].
Jack: Oh wasn't Hilson great?
Craig: He was incredible.
Jack: That was just a lot of fun.
Craig: We've got to have him back.
Jack: Oh, I would love to.
Craig: I found out talking to him after our podcast, he's got all kinds of other cool stories to tell.
Jack: I'm sure he does, knowing Hilson, I am sure he does.
Craig: So, following up on that, we have another special guest, and this person I think has really been influential in the development of surround sound technologies at Dolby.
Jack: That's right, it's Roger Dressler, we're going to be introducing him after the break. He is the father of many technologies here at Dolby, and we're very excited to have him on the show.
Craig: Very, very.
Jack: Now, you might have noticed something a little bit different about our little intro tune, if you're listening in stereo it might sound slightly different. But for those of you that are listening to our podcast through your receiver or your PC with Dolby Pro Logic II or Dolby Pro Logic IIx decoding, you might notice that our intro music was actually encoded in surround sound.
Craig: And there is a reason for that, we actually had a letter from a listener.
Jack: That's right, Andre wrote us, and he said "I'm writing from the UK to thank you for your podcast, which I really enjoy listening to. Like Jack, I'm a fan of electronic dance music..." Very cool "...and find the Pro Logic IIx mode can enhance my listening experience." So do I, Andre, and there is nothing like listening to well-produced dance music through Pro Logic II or Pro Logic IIx, as is similar with other forms of music.
Craig: I'll take your word on that.
Jack: [laughter] and he says that "While listening to your podcast in stereo I decided to flick over to Pro Logic IIx decoding. Then it got me thinking 'Hey, these guys are advocating the use of Dolby sound technologies, why don't they have some demo material to show us how good it can be'" Well Andre...
Craig: Well Andre, we did out beginning introduction just for you.
Jack: There you go.
Craig: And I hope you enjoyed it.
Jack: I hope you enjoyed it; in fact all of our interstitials will be encoded in surround sound today. And Craig and I thought...
Craig: Why don't we move ourselves around the room a little bit.
Jack: Yeah, we might play around a little, so Craig, take it away.
Craig: So OK, I'm in the left channel right now, speaking to you, but I think I'll just swim on over here to the right channel, right across the room, diagonally across your head.
Jack: Hey Craig, where are you going, are you moving back to the surround channels?
Craig: I'm back to the right surround sound Jack.
Jack: Wait, come over here, I'm over on the left surround, I'm going to walk over towards left, what are you going to do?
Craig: Oh man, there's too much room over there on the left, I'm going to sit in the center, why don't you park me in the center there.
Jack: Alright, listen I'm going to come back to the center myself here. And now I am back in the center channel, so that's pretty cool actually.
Craig: Where am I at, I forgot. Am I still in the center or did I go back to right or left?
Jack: Hey Craig, over here.
Craig: OK, OK, I'm in the right channel now.
Jack: Alright, we'd better stop. Those of you listening in stereo are probably wondering what the heck is going on. Plug your iPod or your PC into a receiver with Pro Logic II or you might actually have a PC with Pro Logic II decoding, Pro Logic IIx, and you will hear that entire segment in surround sound.
Craig: Surround sound.
Jack: Which is pretty cool.
Craig: Well, it's really cool, and you know iMovie is coming out now in Dolby surround sound.
Jack: That's right, yeah.
Craig: And with your broadcast content, which is now via Pro Logic and surround sound encoded.
Jack: That's right, in fact all of the movies on iTunes movie store are all surround encoded. But listen, we better move on because we have so much to cover with Dolby Pro Logic II and Pro Logic IIx technologies.
Andre actually had a second part to his question regarding what listening mode he should use when playing back movies encoded in Dolby Digital EX, we're going to be covering everything that has to do with Pro Logic, Pro Logic II, and all those related technologies, here right after we take a break.
[music]
Announcer: Jack and Craig would love to answer your questions, email them at dolbycast@dolby.com.
Craig: And we are back at Dolbycastwith our very, very special guest, Mr. Roger Dressler.
Roger Dressler: Thank you.
Craig: Welcome to Dolbycast,Roger.
Roger: My pleasure.
Craig: Hey Roger, tell us what you do at Dolby, and tell us what you have done at Dolby, because your history here is so rich.
Roger: Yes, I've been here a quarter of a century now.
Craig: [laughter]
Roger: I started when Dolby Surround was just a pup...
Craig: Wait a second, let me get that cobweb, there's a cobweb right there.
Roger: There's more problems than that. And so Dolby Surround has been part of my heritage all along. It's been going on that long. It started with passive decoding, went to the logic decoding, went to digital decoding, and it's just been evolving continuously.
Craig: So passive and logic, tell our listeners what passive decoding and what logic decoding is.
Roger: So passive decoding was a very simple decoder that extracted the surround information, very simple decoder. The logic decoder is what we've been using in the theaters all along, and that's one that we introduced in 1987.
Jack: Wow!
Roger: It's Pro Logic.
Jack: So when I was a kid and I walked in to a hi-fi store, I have this very distinct memory of going into a very high-end hi-fi store, and they had a laser disc player hooked up to a surround sound system. One of my earliest memories was surround sound was this pPassive Decodinglane would fly over [makes airplane sound] and it went to these back speakers, and both me and my parents were standing in the store thinking "Oh my gosh! That is the most amazing..." Now was that logic decoding from back in the late eighties?
Roger: Well that sounds like the movie Always.
Jack: Really?
Craig: Which was a great demo disk.
Roger: And that would've been Pro Logic.
Jack: Wow!
Roger: Yeah.
Jack: Wow, all right, very cool, my earliest Dolby experience.
Craig: So Roger, what's the difference between Dolby Surround as we hear it in the movies, as we hear it defined maybe on television broadcast, and Pro Logic?
Roger: Well, Dolby Surround is really the encoding method, where we take the 4 or 5 channels, make a stereo track for delivery, that's what goes onto the optical film, that's what's coming over your TV. Until we had Dolby Digital 5.1 this is the only way we could get surround to you.
Jack: And that's what you see at the beginning of The Simpsons.
Roger: Exactly.
Jack: Where it says " Dolby Surround". That's what that means, this is a stereo soundtrack but there is surround sound encoded in that stereo soundtrack.
Roger: That's right.
Jack: If you hit Pro Logic II on your receiver, you get that surround sound back out.
Roger: That's right, the surround decoders we call "Pro Logic" because they use high-technology logic decoding to pull those signals out and put them in the right speakers.
Jack: Very cool.
Craig: Very cool. So we started with Dolby Surround in the theater, we went to logic decoding.
Roger: In the theater we went straight to logic decoding.
Craig: Straight to logic?
Roger: That's right, it's was only at the home that we started with the passive decoder.
Craig: OK.
Roger: And that faded out pretty quickly once we did logic decoding at home.
Jack: So what's going on today? I mean, Pro Logic II, you see this everywhere, it's on almost every single receiver, what is Pro Logic II and why is it important in today's world?
Roger: Pro Logic II is the next generation. Not only was it designed to deal with all the existing surrounding encoder content, which would be tons of it, movies and whatnot...
Craig: So you've got compatibility with everything that's out there now.
Roger: Exactly. That's what we call the "movie mode." That takes care of all the previous content. We also added what we call "music mode" which meant anything you've got in stereo would decode beautifully into a surround effect.
Jack: CDs or what have you—anything.
Craig: Now it's my understanding...
Roger: Mostly music. We call it "music mode" but it could be anything that you want to decode.
Jack: Very cool.
Craig: So Pro Logic is actually mono for the rear surrounds, correct?
Roger: It was, yes.
Craig: And then Pro Logic II, when we graduated to Pro Logic II we went to...
Roger: It went to stereo in the surrounds. It added wide bandwidth in the surrounds. It's a much more open and spacious effect.
Craig: So, wide bandwidth meaning it has wider frequency response.
Roger: That's right.
Craig: More bass, more frequency extension.
Roger: Especially more treble, more detail.
Jack: Yeah, I've found listening to Dolby Surround-encoded material through Pro Logic II actually sounds quite close to discrete 5.1, doesn't it? I mean it does a really respectable job.
Roger. It certainly can. Once you get the 5.1 discrete mix you'll hear things that you probably never thought you could, but...
Jack. Right. Right, right.
Roger: But it's a great way to fill that gap. Absolutely.
Jack: Absolutely.
Craig: So the neat thing with Pro Logic II is that if you're a broadcaster, if you're a games provider, and you're basically working in stereo content, you can deliver a surround sound experience to your end user.
Roger: Absolutely.
Jack: Yeah, I've noticed—well actually I've more than noticed—I actually went out there and encouraged many, many game developers to use what we were calling Pro Logic II encoding. So games for a long time were actually encoded with Dolby Surround, which was the 4-channel. It had a mono surround channel. Then we went out with the advent of the GameCube and PlayStation 2, and really went out and pushed game developers to upgrade to Dolby Pro Logic II encoding, which allowed GameCube and PlayStation II to take advantage of the full 5-channel sound field on these new 5.1 channel receivers.
Roger: That's especially important in games where you want to pinpoint and localize something coming up from behind you.
Jack: Right, exactly.
Craig: And if you were watching the Olympics and you were watching and listening in HD and Dolby Digital, you got the full discrete 5.1 surround sound. But if you had an analog television set and you were receiving analog cable signals or broadcast signals, you could still enjoy a 5.1-type surround sound experience through the magic of Pro Logic II.
Jack: Absolutely. Now Roger, we mentioned something in passing, I want to return to it. Pro Logic II you said you have 2 modes. One mode is music mode; one mode is movie mode. I'd actually like to add a third mode, which some people might have in the newer receivers, called "game mode."
Roger: Indeed.
Jack: So in movie and in game mode, it's pretty straightforward. You enable the mode and that's all you really do. But in music mode there are a couple other settings; tell us about those.
Roger: That's right. All these modes are based on exactly the same decoding technology. But music mode gives the user some control—would he like the center channel to be heard from the center speaker only, would he like to spread it out, does he want to have more surround effect, more envelopment or less. Depending on the source material, you might want to make these adjustments. And if you don't want to make adjustments, you can just use the defaults and be done with it.
Jack: What are those adjustments called? What are those parameters called? What will I see on my receiver?
Roger: There are 3 primary adjustments. One of them is the center width control. That adjusts the center image across the three front speakers. Another one is called the dimension control, which literally changes the dimensional space from front to back, and adds the envelopment. And the third one is actually just an on/off switch we call the panorama control, which can wrap the surround effect around you. So things that are only in the left and right fronts can now wrap around to the surround; it's quite exciting.
Jack: Very, very cool. Well, listen everyone; we're going to go to a musical break. You might notice as we go to this break that it has been encoded with Dolby Pro Logic II. You should hear things swinging all around your room, and panned in all your various speakers. If you're listening in stereo, again, we highly encourage you to get a PC with Pro Logic II or Pro Logic IIx, or just plug it into your receiver.
Craig: Plug it into your receiver.
Jack: Well listen, we're going to go to the break. When we come back we're going to cover the latest and greatest, Pro Logic IIx.
Craig: And speak to another technology.
Jack: Sounds good. We'll be right back.
[music]
Announcer: For answers to your audio questions, email dolbycast@dolby.com.
Jack: And we're back. Ladies and gentlemen, welcome again to Dolbycast. I hope you enjoyed that musical interlude.
Craig: You know, Scott, our producer, reminded... And Scott, he's the kind of guy that does this all the time.
Jack: Yes, he will remind us that we forgot to talk about specifically, Roger, game mode. How is that different from movie mode?
Roger: Game mode was specifically designed to take advantage of the fact that gamers really want to hear all the detail they can from the back channels, and that means the bass, too.
Jack: Right.
Roger: So we changed the way the bass is handled in the decoder to give you that effect. Like when huge spaceships fly over your head or a cannon goes off behind you, you won't lose that bass.
Jack: That's very cool. Game mode is actually my personal favorite mode, being a huge fan of bass, as our regular listeners might know. I actually find it's actually very cool. I will use game mode even for listening to my movies. That's just my own personal preference.
Roger: Well, Jim Fosgate likes to listen to his movies in music mode.
Jack: There we go! Well, listen, Craig; I want to toss it back over to you to read the second half of Andre's listener question, which should bring us into the second half of our podcast, which is regarding Dolby Pro Logic IIx.
Craig: So, Roger; Andre writes "Should I use the standard Dolby Digital EX decoding option on my receiver when watching movies or should I use the Pro Logic IIx decoding option all the time?"
Jack: And this is specifically regarding movies that are encoded in Dolby Digital EX.
Craig: So, what is Dolby Digital EX, Roger? And what is Dolby Pro Logic IIx? And talk about the compatibilities and how they work together.
Roger: Now that we're talking about EX we're into systems that have more than 5.1 channels. Dolby Digital is a 5.1 channel system. You play it over your 5.1 speaker system. EX adds another channel—that's the back surround channel. To get that into the Dolby Digital system, it's matrix encoded. So instead of just mixing 5 down to 2, as we did with our stereo delivery, we're mixing 6 down to 5.
Jack: So Dolby Digital EX is 6.1?
Roger: It is.
Jack: OK, so if I have 7.1 what do I do?
Roger: The reason you have 7.1 by the way, is because the EX channel should be played back over at least 2 speakers. You don't want a hot spot behind you. So we always recommend to have at least 2 speakers back there, even if you have an EX decoder with a 6.1 output.
Jack: Oh, OK.
Roger: And that's why 7.1 became popular. Now you have 2 back channels, or 2 back surround channels.
Jack: Why not feed them separately, yeah.
Roger: And why not feed them separately? So PL IIx helps you feed separate signals to each one. If you have a Surround EX decoder that has a PL IIx option in it that should actually be the default. We've recommended to the manufacturers that it automatically default to the PL IIx option when you get a Surround EX signal.
Jack: So, when listening to a movie that is Dolby Digital EX encoded, you would tell our listeners, "If you have Pro Logic IIx, go ahead and use it."
Roger: That is right because it will do everything any EX decoder will do but also does some things better like lateral pans across the surrounds come out a little bit more pinpoint accurate.
Jack: Very, very cool. Now, some receivers though will have — some older receivers, specifically — will have Dolby Digital EX decoding but might not have Pro Logic IIx. It is only the latest and greatest receivers that have Pro Logic IIX. Is that true?
Roger: Well, that is right. And if you do not have PL IIx, you do not have to worry about. If you only have 6.1 speakers connected, you do not have to worry about it. PL IIx can't be offered, in that case, with 7.1 mode. But now, again we also have to talk about music mode and movie mode for both of those. I'm sorry.
Jack: We hit— do not worry Roger, we hit the microphone every episode. It is kind of a tradition of ours. "[both laugh] So you listeners, you might have heard of "poobfs."
Craig: Speak for yourself, Jack.
Jack: Now, listen. So, what happens if I have just, like let us just say, I have a Blu-ray disc with a 5.1 channel soundtrack, should I go ahead and enable Pro Logic IIx if I have 7.1 speakers?
Roger: I would.
Jack: Even if it is not EX encoded, it is perfectly fine.
Roger: That is right. And that is why we have a movie mode and a music mode. So, if you like the effect of using all your speakers to the best advantage, you can select those modes and turn it on all the time.
Craig: Remember the Pulse disc I have been talking about, the Pink Floyd disc?
Roger: Yes.
Craig: That is 5.1. I put it on my 7.1 system. It is absolutely incredible!
Jack: Using Pro Logic IIx?
Craig: Using Pro Logic IIx.
Jack: Very, very cool.
Craig: The other cool thing is not only 5.1 content is compatible with PL IIx but also 2-channel content. Right, Roger?
Roger: Absolutely. PL IIx will take any 2 channel or 5.1 channel source and give you a 7.1 output.
Jack: Now, with the newest connections like HDMI. We are talking about Blu-ray and HD DVD. Moving forward, a lot of this content we expect to be discrete 7.1. But today we do not see a lot of that content. Most of this content on Blu-ray and HD DVD is still 5.1. I guess my question is 2-part — does Pro Logic IIX fill the gap if I have a 7.1 system today and will it work if am using an HDMI connection?
Roger: HDMI is a great way to bring the digital decoded video straight across to your AVR. And most of these AVRs can take that PCM signal and post process it. You can add PL IIx and other effects and it will work just the same as if you were decoding the soundtrack right in the AVR.
Craig: Yes. It should be mentioned. The True HD track, the Dolby Digital Plua track, is decoded inside the player and that decoded signal is converted into a PCM signal.
Roger: Which is 5.1 and that comes over to you AVR and then again. Just the same deal.
Jack: Process it.
Roger: You can have PL IIx.
Jack: Very, very cool. So, listen. I have a new receiver at home with 7.1 channels. Just picked it up. And I have been using 5.1 speakers for a long, long time. And I was actually going to hold off buying a couple of extra speakers for this new 7.1 receiver because I figured, “well geez, there is not a heck of a lot of discrete 7.1 content out there.”
After this conversation, it really makes me think that Pro Logic IIX might fill that gap, might give me a reason to go 7.1 with my speakers. My question to you is what does that bring to the table if I get 7.1 now? If I go ahead and get those extra 2 surround speakers, what am I going to hear differently?
Roger: You are just going to hear a better sense of space. That is what is all about in surround. It is not always about pinpoint effects coming from direct speakers. It is about envelopment and naturalness. And, by the way, these decoders are not adding sounds. We are not adding reverb. We are not adding any new sounds. It is only what is in the soundtrack being played over these additional speakers.
Jack: So no effects. No additional reverberation. No nothing. It is just taking the sound that already exists.
Roger: That is right. And extracting the spatial cues and using that to direct the sounds to the speakers.
Jack: Sounds like I have to hook up those 2 extra surround channels and get 7.1 going in my system.
Craig: Hey, Jack, have you ever heard of a band called Led Zeppelin?
Jack: I've never heard of Led Zeppelin.
Craig: Never heard of them?
Jack: What? - [laughs] Of course, I have heard Led Zeppelin. What is the—? Go ahead.
Craig: We actually use a clip from Led Zeppelin, Whole Lotta Love, and, you know, the drum solo in the middle of that. Put that on your system at home, people, and listen to that in Dolby Pro Logic IIx and the effects are absolutely phenomenal.
Jack: What does it do?
Craig: The sounds just swirls all around your head.
Jack: No kidding.
Craig: It is very, very cool.
Jack: The original recording?
Craig: The original recording.
Jack: Oh, very cool!
Craig: And that's a stereo recording!
Jack: Very cool. Is there anything else that really brings out the effect?
Craig: What I remember when we were introducing the Pro Logic IIX is one we used, Roger, was Das Boot which was a great Dolby Digital 5.1 demo when it first came out. But in one of the scenes where the submarine is descending through the depths and the pressures start increasing on the submarine, the bolts inside the submarine starts popping.
Jack: Yes. I remember that.
Craig: In one of those scenes, a bolt actually pops in the left front speaker or in the left front soundstage really, goes diagonally across the soundstage to the right surround and then rolls behind you.
Jack: Oh, that must be great!
Craig: And all of this is possible with PL IIx.
Jack: So, if you have a 7.1 system, that is the scene, is it not?
Craig: It is a killer.
Jack: You know there is another actual piece of demo content that we are often used when demo-ing both Pro Logic II and Pro Logic IIx. It was a game, actually on GameCube, called Rogue Leader. It was published by LucasArts and developed by our friends up at Factor 5. It was the first game ever in Dolby Pro Logic II.
Craig: So, it was 2-channel?
Jack: It was... Well, the GameCube is only capable of, really, an analog stereo output. So, Dolby Pro Logic II enabled the GameCube to support 5.1 channel sound even though it is really intended only for stereo. And when this game came out, they actually included a special section in the Options menu, I believe it is in the Options menu, called Sound Test and you had a TIE fighter that started in the center, fly over your head, and then rotate around the sound field, and hit all 5 or all 7 speakers, as it kind of swung around your head. You could let that run. Boy, that was really a cool demonstration.
Craig: So, we were literally taking 2-channel and making it 7.1 surround field.
Jack: Absolutely! Well, that is actually what Pro Logic IIx can do! Not only take 5 to 7 but 2 to 7. And listen. Hopefully, we have given all you listeners out there plenty of demonstration material including every movie in iTunes movie store. You got Das Boot, you got Rogue Leader, you got this podcast. We have Dolby Surround material, Dolby Pro Logic II material for days.
And listen. Thank you all for listening.
Craig: And thank you, Roger Dressler.
Roger: My pleasure.
Jack: And thank you Andre for the listener question. We love answering listener questions, don't we, Craig?
Craig: We definitely love that.
Jack: All right! Well, that is a wrap. Thank you for listening to Dolbycast. Please send in your questions.
[music]
Craig: I am Craig Eggers.
Jack: And I am Jack Buser. Tune in next time.
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