DD vs DD+ (1 Viewer)

[Jari K]

I hope this isn´t a stupid question (and despite the title, I don´t want to start any debates nor "format war"), but I´m a bit confused about "Dolby Digital" (Blu-ray) vs "Dolby Digital Plus" (HD DVD).

I have thought that both can use the same bitrates (640kbps or 1.5mbps AKA 1536 Kbps), but now some people are saying (or implying) that "DD+" is a "better audio format" than "DD". Now what´s the truth?

Just to point out, that I´m fully aware that certain HD DVD-releases are using 1.5mbps audio, while the same title in Blu-ray has 640kbps. In those cases HD DVD (on audio) has the edge.

My question basically is, that are DD and DD+ essentially "different"?

Thanks a lot.

 

[Michael TLV]

Greetings

DD+ when at 640 kbps is the same as DD on Blu. Roger Dressler from DolbyLabs has mentioned this.

Apparently HD DVD can't do regular DD higher than DVD levels for KBPS ... so they have to go to DD+ to deliver the 640 ...

The DD implementation on Blu allows regular DD to go to 640 kbps.

(This came from Roger as well in a thread a long time ago.)

Regards

 

[Doug Schiller]

Wow, that makes no sense to me whatsoever.
I thought these were completely different codecs.
Plus, my regular DVD can do 640k, why can't my HDVD do it?

 

[Michael TLV]

Greetings

Regular DVD does not do 640 kbps ... it's either the 358 kbps or the 4xx kbps variety.

Even DVHS only did 5xx kbps.

Regards

 

[ChristopherDAC]

Because of the way the data packets are structured, DVD can run Dolby Digital AC-3 at up to 448 kbps ; HD-DVD can run up to 504 kbps. AC-3 doesn't go any higher than 640 kbps, which is what is used on Blu-Ray.

"Dolby Digital Plus" is Extended AC-3 (E-AC3). It incorporates improved coding models which preserve more audio information when used at low bitrates (such as 192 kbps). Additionally, it allows for additional data from channel arrangements beyond 5.1. Specifically, in the case of 7.1 audio, it supplies the 4 rear channels as a separate packet : there is a 5.1 core, and then an extension which replaces the 2 rear channels of 5.1 with 4 new rear channels.

This has been covered here, but in a thread I wouldn't care to search.

 

[Michael TLV]

Greetings

Thanks Chris.

Regards

 

[Jari K]

Thanks for the info (both Michael and Christopher).

So basically both are identical in 640 kbps?

How about the 1.5mbps -issue? Why Blu-ray doesn´t use that (only 640 kbps so far?), when HD DVD has 1.5mbps in selected releases? Is this connected to "DD vs DD+"-issues?

Sorry about the questions, but I´m still a bit confused.

 

[Michael TLV]

Greetings

Currently Blu does not use DD+ on anything so no 1.5 mbps tracks.

DD can't go out to that ... being limited to the 640 ceiling.

Blu usually decides to go to PCM / DTHD / DTS HD or MA if they want more. Speaking of which ... they could just do DTS which is 1.5 mbps ...

So why doesn't Paramount do that? Why 640 on the Blu side and 1.5 on the HD side? Only they know that answer.

Neutrality isn't what it used to be.

I recall reading a comment from Roger Dressler about 640 versus 1.5 and it was something to the effect that he/they felt that the results were similar so no need to go there.

Regards

 

[Jari K]

Thanks again.

So conclusion basically is, that with 640 kbps both DD and DD+ are identical, but with 1.5mbps DD+ has the edge (since DD can´t go that "high").

DD+ can also have 7.1, while DD is limited to 5.1 (not that HD DVD has been using 7.1 on DD+..).

I´m not sure why Blu-ray can´t also use DD+ (instead of DD).. Well, viva format war.

 

[Jeff Adkins]

Paramount did this with some early BD titles. I believe Sky Captain and Lara Croft:Tomb Raider have 1.5 m DTS tracks on them.

DD+ was originally designed as a way to have 7.1 discrete channels with a lossy codec. BD only supports DD+ with 7.1 channels whereas HD-DVD allows it to be used with 5.1. Do a search on the Dolby "white papers" and you'll find so much info on this your head will spin.

 

[Jordan_E]

I'm going to have to rent We Were Soldiers on Blu some day and compare, because the DD+ on that HD DVD title is amazing. The soundfield has so much depth all the way around.

 

[Doug Schiller]

Well I guess my 640kps Pink Floyd Pulse DVD will be worth a fortune since it runs at 640kps.

Either that or its lying to me.

So, back to my original question on that reply, does anyone else buy the theory that 640 DD = 640 DD+.
I can't fathom that anyone from Dolby would admit that a late 80s codec is exactly the same as one that was developed in the last few years.
If so, maybe a link to where Dressler said that would be appropriate.

 

[Jordan_E]

Man, I keep forgetting I have that DVD (didn't like that particular concert at all; I think it was the 2nd drummer who kept hopping and jumping like an idiot!). Going to have to spin it soon.

 

[Doug Schiller]

Here is an interesting link that may clear up the confusion on the DD = DD+ claim:

http://www.us.design-reuse.com/artic...icle14692.html


Therefore, if you use a S/PDIF, the processor will downgrade the stream to be the same as DD.
So if you are using a standard digital output (S/PDIF) with both formats, you will get the same result.
I doubt it will be the same if you use HDMI on both.

 

[ChristopherDAC]

Look, we've been around and around this bush. The quotes you want are in some of the more violent HD-DVD/Blu-Ray threads, and there's no sense dragging that out. The differences between AC-3 and E-AC3 are: E-AC3 provides a new set of coding models for higher sound quality at low bitrates (higher CODEC efficiency) ; E-AC3 allows for an "extension packet" alongside the "core packet", providing for 5.1 and 7.1 audio without quality compromise (essentially an admission that DD-EX has not been a success). At 640 kbps, neither of these applies.

If you want more details, I can refer you to various white papers and technical specifications, but this much should be clear : "Dolby Digital Plus" is not a new CODEC. It is a set of extensions to standard "Dolby Digital". (Your Pink Floyd DVD must have another DD or PCM soundtrack on it, because 640 DD can only be coded on a DVD in the types of packets normally used for dts soundtracks, not in the "default audio" packets, as I recall.)

 

[Doug Schiller]

I don't think we have been around the bush so much. This is the first time I'm seeing some real information.
You have answered all my questions, thank you.
I have read some of the white papers, and they don't come out and say it but yes, it is an extension of DD, not a new codec.
And yes, the Pink Floyd DVD does have other soundtracks (DD and PCM I think).

I just wanted to hear some real info instead of the "so and so said on another thread".

D

 

[ChristopherDAC]

Sorry, it's just that in some of these other HTF threads to which I was referring, there were people who would knee-jerk deny even quotes from Dolby's own papers. The ATSC has a quite extensive document on E-AC3 under "A53", the audio coding section (since standard AC-3 was adopted for digitial TV years ago).

For reference, AC-3 was originally designed to deliver theatrical 5.1 audio at an "acceptable" quality level with a bitrate of 320 kbps, which was the maximum that Dolby's engineers could fit into an optical track printed between the sprocket holes of 35mm film prints without reliability problems. The difference between theatrical AC-3 and the 384 kbps allowed by LaserDisc RF encoding is supposed to be considerable ; at yet higher rates, such as DVD-s 448, or 640 on BD (the maximum supported bitrate), it is supposed to sound very good.

AC-3 is based on AC-2, which was designed in the early '90s for stereo audio broadcasts on satellite TV, using a bitrate of 192 kbps. In fact, the "DD 2.0" you see on DVDs is really AC-2, which became the stereo subset of AC-3, and has certain special rules which pertain only to it. Better results can be had by using full-spec AC-3 in two-channel mode at higher bitrates, but AC-2 is the default for DD encoders presented with two-channel material.

The two are unrelated to AC-1, a late-'80s reduced-bitrate audio coder developed for "DVI", a CD-ROM format which became the CDi and VCD. Whereas AC-2 and -3 use a sub-band coding system, AC-1 was based on DPCM, working in the time domain rather than the frequency domain. "AC" stands for Audio Coder, by the way.