Dolby Pro Logic II vs. Dolby Digital Pro Logic II?

Andy_Munich · 10-01-2005, 07:21 AM

I recently rented the game "Genji: Dawn of the Samurai" for the PS2 from GameFly. I therefore do not have access to the game's manual.

The game featured more audio options than I am accustomed to. Besides the normal sliders for BMG and Effects levels, there was a choice of four sound formats. Mono and Stereo were present and expected. What puzzled me was that I could choose between Dolby Pro Logic II and Dolby Digital Pro Logic II. Since neither of these options is true Dolby 5.1, I was curious what the difference was. Anyone think they know?

BTW, the game also allowed you to choose an audio reference point. Player, Camera and Realistic were all options. I was very impressed by the audio presentation of this game. It has a beautiful soundtrack. I wish I could say the same about the actual game-play.

Arthur S · 10-01-2005, 10:31 AM

I will venture a guess.

Dolby Pro Logic is analog. Dolby Digital is digital.

For those who have digital decoder in a computer or audio reciever, they can use Dolby Digital.

Dolby Digital comes in various flavors. The newest are 5.1, however, Dolby Digital Pro Logic is a 2.0 channel (digital) mix.

Anyone else, please feel free to jump in and add further clarification.

Kevin C Brown · 10-01-2005, 04:41 PM

I would agree. If you know that the Dolby Digital DPL II is not 5.1, then it only makes sense that the DPL II option is analog and that DDPL II is a digital 2.0 output.

John S · 10-03-2005, 05:05 PM

It is becomming more common....

DPLII is a real format. I have been told that
very soon you will start to see 5.1 / 6.1 / 7.1 mixes done in DPLII / DPLIIx as real other descreet multi-channel format and not DD 5.1 / DD 5.1 EX.

Already many have found lots of benefit running DD5.1 mixes through there DPLIIx processors, so it is a cool developemnent in HT as far as I am concerned.

MikeUp · 10-03-2005, 07:08 PM

I'm new to so much of this terminology. Am I right in assuming that the primary purpose of DLP II is to satisfactorily play a 2-channel source (a typical CD) through a 5.1 speaker configuration?

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JeremySt · 10-04-2005, 03:48 PM

Mike: yes. As well as 6.1 and 7.1

JeremyErwin · 10-04-2005, 04:33 PM

PCM stereo consumes a lot of bandwidth. A 48Khz/16bit/stereo signal consumes about 1536 kb/s. If you had a 4Mb/s interface available, you might be able to send 5.1 channels of sound (the lfe channel doesn't require the bandwidth of the others-- probably needs a sampling frequency of 240 Hz or so). But SPDIF isn't that capacious. Besides, spending half ones bit budget on audio isn't the wisest move when mastering a DVD.

So, it's compressed. Dolby Digital has a maximum bitrate of 640 Kbs. 384, or 448 is quite common. dts uses either 768 or 1536 kbs when applied to dvds. Laserdiscs and CDs probably use 1411 kbs.

The problem is that compressing the audio is computationally expensive. The XBox accelerates this-- but the PS2 would have use a CPU that could be better used for graphics, gameplay, or something else. Rendering the 5.1 audio stream into an uncompressed PCM stereo signal is much less so.

There's a side benefit, too. Any audio details that would have been discarded by an aggressive lossy compression algorithms will still be present. However, the surround channels won't be discrete, and certain effects won't be as dramatic.

Cut scenes consist of prerendered material, and the playstation is not required to compress the audio. If the player wishes, he can set the PS2 to use dolby digital for cut scenes (preserving the channels discreteness), and PLII for everything else. A player who doesn't own a dolby digital receiver would just use the Dolby Pro Logic II soundtrack, and in all probability, the resulting audio would be played back using Dolby ProLogic, or ordinary stereo.

Dolby ProLogic IIx extracts back channel information from 5.1 soundtracks. Somehow it does this without crushing the rear soundstage, as Dolby Digital EX is often accused of doing. I suppose it would be possible to master a 5.1 source specifically for 7.1 playback, in much the same way that modern "dolby surround" tracks are tweaked to take advantage of the PLII algorithms.

But a movie eschewing 5.1 sound for a 2.0 "surround mix"? Probably not going to happen.

Kevin C Brown · 10-04-2005, 09:00 PM

Quote:

DPLII is a real format. I have been told that
very soon you will start to see 5.1 / 6.1 / 7.1 mixes done in DPLII / DPLIIx as real other descreet multi-channel format and not DD 5.1 / DD 5.1 EX.

No. DPL II and DPL IIx are decoding algorhythms. For 2 channel, you *can* encode them via "Dolby Stereo", but that's it. There is no, and will never be such thing as a DPL II(x) encoded soundtrack.

And obviously, both DPL II and IIx can be used to decode generic stereo recordings like music CDs.

Dolby Digital is a specific encoding algorhythm. For DD EX soundtracks, the 6th channel is matrixed into the surrounds, but it is still vanilla 5.1 Dolby Digital encoding. DD EX soundtracks usually sound better with DD EX decoding, but nothing special is happening during the encoding.

John S · 10-05-2005, 11:38 AM

I somewhat beg to differ...

Running recording studio(s) at various times in the past. You can get the software to mix to 2 channel DPL and DPLII and DPLIIx all different softwares.

I actually think the 5.1 that will use it, will be more or less regular 5.1 made to have DPLIIx run over it instead of EX queues. Another psuedo 6.1 / 7.1 sound mode for them.

Kevin C Brown · 10-05-2005, 08:25 PM

If that is so, please post a link to software that can do this.

I personally have never seen a DVD that had "mastered for DPL II(x) playback" printed on it.

FeisalK · 10-05-2005, 09:59 PM

Dolby says this on their website

"In addition to enhancing playback, Dolby Pro Logic II can be used to encode TV programming to deliver a surround sound experience for viewers with stereo TV systems."

... whatever that means

stereo source -> DPLII matrix processing -> 5.1 channels -> stereo downmix??