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PCM5.1 & lossless audio discussion - split thread from A Knight's Tale review


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#1 of 119 OFFLINE   Michael Osadciw

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Posted July 26 2006 - 11:03 AM

Hi David

I've been waiting for the day when uncompressed PCM is used. Sure, it gobbles up video space, but I think in the future with higher capacity discs and a more efficient video codec this is nothing to worry about. I think people are too fearful of that based on some of the bad titles on DVD with multiple audio soundtracks. I say "guess what??" to those people: "It's not all about video, my friends." I expect the highest quality audio experience possible. Yes, I appreciate great looking video, but my passion for audio is just as much if not just a little more. I love hifi and love my home theater's ability to reproduce high resolution audio (although admittedly I can still do better...and will). I get a great experience out of it.

Some may say that if I was looking for a hifi experience I shouldn't listen to film soundtracks - that is true for many reasons, but that doesn't mean that I should settle for lossy compression formats that sound worse than the quality of a CD. We're in the age of trying to surpass the sound of CD and lossy DD/DTS isn't the direction to take. Unfortunately space limitations on DVD forced the use of DD/DTS - there just isn't enough space on DVD...but now with these new HD disc formats (HD-DVD/Blu-ray) there is enough space (so is said by the makers). "What about space for special features?" some may ask...they can always go on "disc 2" like they do with DVD today. Who says everything MUST be on one disc??

Anyways, PCM, as you can figure out on your own, BLOWS AWAY any of the lossy compression formats which at one time claimed to be "transparent" to the source. That's a load of [ ]...just to make consumers accept it, maybe? DD/DTS are businesses and they have to do what they have to to survive in the marketplace...to get royalties to be put on DVDs and players...I don't think it would be good for their business if we all switched to uncompressed multichannel PCM, would it? Would I care? Nope - they'll have to learn to adapt in other ways because there is still a need for compressed audio in the market - but not for a complete HD-Experience (HD-Ex I should call it and trademark it) - sound & video that surpasses all before it - that's all I care about.

PCM on laserdisc always sounded better - DVD was a step backwards for audio but now Blu-ray is proving we can take steps forward (on these Sony releases). Honestly, I don't trust lossless Dolby TrueHD or DTS-HD master audio...it's still compression and I'm sure they have their own sonic signature to the sound (remember they promised their lossy codecs were transparent!) With audio anything can get in the way...it's a finicky and sensitive hobby (both the technology and the enthusiasts!) And for those computer people out there who may argue me on this...I don't compare this to .zip files etc...I'd be very surprised if either lossless audio compression formats blow me away as uncompressed PCM audio did. So far Dolby Digital Plus has done little to impress me - you still have to "listen hard" to hear it.

Sony has mentioned that uncompressed 24/96 PCM "is coming" on Blu-ray and that is exciting. I imagine once 50Gb discs are available we may start seeing this. I believe THE FILM is the #1 priority and all else is 2nd. I want the highest performance possible especially since I can see/hear it.

Even though the PCM on these discs are 16/48 - it's not inferior to DD/DTS that discard all of those fine details we are supposed to appreciate from the 24/48(24/96) audio masters they encode. With uncompressed PCM, we are supposed to be hearing all of 16/48 - no loss in detail, no compression. Listening to it makes you realize what we've been missing all this time. What really blows me away is that I'm hearing it through fairly cheap DACs in the Samsung player. Once connected with HDMI to a preamp/receiver with reputable DACs I believe the differences will be even greater.

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#2 of 119 OFFLINE   DaViD Boulet

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Posted July 26 2006 - 02:45 PM

Mike,

great coments. I agree 100%. I was an audiophile long before getting into LD and DVD and know how good a turntable can sound powered with a tubed amp...

Posted Image

BTW, Dolby True HD and DTS-HD lossless will be nice because they'll save 50% over traditional LPCM (still lossless).

dave Posted Image
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#3 of 119 OFFLINE   Neil Joseph

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Posted July 26 2006 - 04:04 PM

Quick question guys, and sorry if I temporarily steer the topic off course but, with pcm5.1, does this make 6.1 a mute topic? What about the rear centre speaker(s), do they come into effect still for any of the pcm5.1 soundtracks, or is it on only on a title-by-title basis? Take the upcoming Stargate for instance from Lionsgate. The DVD had a 6.1 soundtrack so will the new pcm5.1 soundtrack have the same "effect" or will the receiver have to be forced into 6.1 mode to play the rear surround speaker(s) ala 6.1 mode?

I too love the fact that this particuar audio format is available on some/most titles and I hope that they keep it up permanently now, and when BR50 comes out, that it does not go the graveyard like fullbitrate dts did on dvd. This is one of the reasons that I will be getting into blu-ray once Sony comes out with their player. It is nice to be able to enjoy a truly lossless audio format now, rather than having to worry about upgrading to hdmi1.3 especially since my receiver is pretty doggoned new already.... Yammy 2600

That said, I am waiting eagerly for this particular film (A Knight's Tale). I remember the first time watching it and thinking that it was weird but this film really grew on me each and every time I viewed it and has become one of my, and my kids, favourites from this studio.
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#4 of 119 OFFLINE   AlexBC

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Posted July 27 2006 - 02:12 AM

Great post about the audio Michael.

PCM is the grand goal for me on HD. Like you, as much as I love a great HD image, I think I still care a little bit more about the audio department (guess that's why I still watch tons of LDs).

Like I stated on a previous thread when HD foruns started, original soundtrack on PCM for all titles is the most important thing right now for me on HD formats. And like you, I also don't trust any of these lossless compression just yet (although they have the benefit of eliminating jitter as they can be sent as bitstream to a decode-capable surround receiver or processor).

From what I've seen up until now, my fears are comming true, no original lossless soundtrack for catalog titles:
http://www.hometheat....d.php?t=233241

Thanks for the review ; )
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#5 of 119 OFFLINE   DaViD Boulet

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Posted July 27 2006 - 03:14 AM

Guys,

Lossless is losselss. Relax!

It's one thing to worry about trusting lossy algorithms... but let's not get bent out of shape with lossless compression (ie, a zip file).

The real worry for me would be *other* meta-data settings like dialog-normalization that Dolby might try to throw into the mix that compromise auido quality in other ways.

Hopefully Dolby True HD and DTS-HD lossless will get used *soon* as we'll then have space for 24/96 resolution!

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#6 of 119 OFFLINE   AndreGB

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Posted July 31 2006 - 03:46 PM

Quote:
Originally Posted by Michael Osadciw
Honestly, I don't trust lossless Dolby TrueHD or DTS-HD master audio...it's still compression and I'm sure they have their own sonic signature to the sound (remember they promised their lossy codecs were transparent!)
Oh dear Michael, please, don't make us engineers cry. Posted Image Transparent and lossless are different things. Transparent should sound just like the original thing, but it doesn't (marketing maybe). An audio codec created more than ten years ago can't do justice to the equipment we can have today.

Now lossless is lossless. Think like this. Type your name on notepad, save it as name.txt and compress it using zip. Then uncompress it on a different folder and voilá, there is your name, same letters, same spaces. Digital information is all the same, be it text or audio data.

Lossless compressed audio is transformed back into PCM to feed the DAC on your receiver. This PCM is the same as the one used to compress the track. Why compress it? Because any space saved due to compression is profit. You can use it to increase the bitrate on the video stream while not altering the audio track. This is how engineers think. If we can achieve the same thing using less space, less money and/or less time, then that's the approach we should take. Posted Image

Worry not. Lossless is lossless. 01011 is 01011. Posted Image Posted Image

#7 of 119 OFFLINE   AlexBC

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Posted August 01 2006 - 03:44 AM

AndreGB

I can't speak for Michael, but I believe that his concerns are more in line with mine. I'm not arguing that a 'true' lossless compression algorithm is not lossless, as you said, they are bits for bits identical.

But what I don't really trust is their word, if you get me. I mean, since I haven't had any access to their code (and from what I know, nobody outside Dolby knows it either), for all I know this could be some kind of marketing gimmick. We simply have no way to actually verify if the decompressed data is identical to the master, like when you decompress a ZIP file as you accurately put.

Considering the big corporations track record, I think we can safely assume that not everything that's advertised is exactly what it states. So, for now, while I don't see some analyses by an independent part or another kind of proof, I just don't believe them a 100%.

To further enforce my point that Studios' (and corporations in general) marketing can't be blindly trusted, see what has been the case up to now: both Sony's PCM tracks as well as Warner's DTHD are from 48/16 masters. That means they're not really top quality as the studios want us to believe, because I haven't seen any kind of info on their releases stating their bit and sampling ratios, but they clearly state "master quality".

They can be master quality, duhh, but not best master quality. Ohh so much crap...

BTW, are you my great friend a.k.a. Rash? : )
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#8 of 119 OFFLINE   DaViD Boulet

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Posted August 01 2006 - 03:55 AM

What worries me is Dolby's history of compromising audio qualtiy when it was entirely unnecessary... and how this might extend to their Dolby True HD encoding/playback.

Most folks aren't aware (and it shocked me to learn) but the dialogue-normalization setting that's ubiquitously applied to DD soundtracks actually forces the decoding chips to apply digital attenuation... ie DSP which recalculates all the data resulting in a LPCM signal that looks nothing like what came right out of the Dolby decoding engine.

In fact, I suspect that this is one of the main reasons why DTS often "sounds better" to many listeners on DVD. When I listened to the DD track on the Lion King and remarked to the audio engineer who mastered the disc "Wow... the DEHT DD mix sounds like DTS" he replied "we didn't use any dialogue normalization". That should tell you something.

In any case, the problem with Dolby is that they view these "features" of their algorithm as enhancements rather than as signal-processing that removes fidelity (which is the fact of the matter). In fact, they default their DD encoders to apply a base-line of dialogue normalization so an audio engineer would actually have to understand the issue and manually override the setting to get a true "flat" encoding that wouldn't force data-recalucation upon playback.

Who knows what other "features" Dolby might throw into the mix for audio codec use on HD DVD/BD. At least DTS tends to take a "less is more" audiophile approach. I'm hoping that DD has learned some things about high-end audio reproduction with their advances with DD+ and Dolby True HD and doesn't take one step forward and another step back with low-fi features like dialogue normalization.
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#9 of 119 OFFLINE   Max Leung

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Posted August 01 2006 - 07:11 AM

There is some great audio discussion here. If only all thread hijacks are this good. Posted Image

The only way we can know if Dolby TrueHD is actually lossless is to wait for the authoring tools to become widely available...then someone could grab a PCM multichannel track and compress it with a TrueHD authoring tool, then play it back, checking bit-for-bit.

Like David, I think dialog normalization is evil! I'm no audiophile - but I am really disappointed with the low quality of some of the DD5.1 tracks out there. Yuck.

BTW, is "A Knight's Tale" encoded as mpeg2? Also, Mike, have you verified if the Samsung Blu-Ray player passes blacker-than-black and peak-white information? Does it expand to PC levels? I'm wondering if that is why you don't see any mpeg2 compression artifacts...(yes, I have a low opinion of mpeg2!)
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#10 of 119 OFFLINE   Neil Joseph

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Posted August 01 2006 - 07:48 AM

Holy thread hijack Posted Image I am actually pondering splitting this thread into two separate threads... (1) the review and (2) the audio discussion.
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#11 of 119 OFFLINE   AlexBC

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Posted August 01 2006 - 08:55 AM

David,

once again you hit the nail on the head ; )

I've had enough with compromises on A/V software, specially silly compromises like the Dial. Norm. you say. Maann that things is mean : )

I sorry I'm dragging this further off topic, but regarding the Lion King presentation you mentioned, I've been able to compare the DD 5.1 DEHTM on the R1 NTSC DVD to the DTS 5.1 DEHTM on the R4 NTSC DVD and yeah the differences are much narrower than I usually find when comparing regular DD and DTS tracks. I guess you found out the explanation for that
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#12 of 119 OFFLINE   DaViD Boulet

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Posted August 01 2006 - 09:13 AM

Alex,

especially sad when you think that the rest of our DD DVDs could sound better were dialog-norm not applied! (flag set to 0). Thanks for sharing your impressions... I had heard from others that indeed the DD and DTS encoding sounded much closer than the usual (presumably due to the lack of dialog norm on the DD track).

Ok... back on topic!

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#13 of 119 OFFLINE   AndreGB

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Posted August 01 2006 - 03:01 PM

Can I keep it a little longer off-topic (or someone could please suggest an existant topic where we could discuss this?). Posted Image

Yes, Alex, I'm Rash. Posted Image Anyway, I have already played around with MLP and it is, indeed, lossless. I've encoded PCM to MLP and back to PCM and both PCMs were bit-by-bit identical (using bit comparison).

So as long as Dolby TrueHD is really using MLP code, then I'm satisfied. You see, uncompressed PCM is a waste of space, that could be used for better video quality (important for HDTV video), for example.

Now tell me, please, what does this Dialog Normalization does? I've seen Dial Norm on my encodings but never really used it. I'm a "the least processing the better" kind of guy. What does it do? Why do they use it? I know this is way too off-topic, would you reply me privately or suggest me to open another topic, please? Thank you.

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#14 of 119 OFFLINE   Neil Joseph

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Posted August 01 2006 - 04:35 PM

Guys, I have spun off these posts from the Knight's Tale BR disk review thread. Please feel free to continue with these very interesting discussions on the newer generation audio formats, within this thread.
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#15 of 119 OFFLINE   Ed St. Clair

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Posted August 01 2006 - 06:30 PM

Quote:
Originally Posted by DaViD Boulet
Hopefully Dolby True HD and DTS-HD lossless will get used *soon* as we'll then have space for 24/96 resolution!
Maybe this thread could also be used as a listing of "lossless" HD disc titles.
Both, BD & HD DVD.

Thanks for this audiophile, for videophiles, thread!!!
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#16 of 119 OFFLINE   Ryan Wong

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Posted August 01 2006 - 09:25 PM

This is what I read from Dolby website (http://www.dolby.com....0925_Final.pdf):

"21. Does Dolby TrueHD feature any metadata applications? What are they? How will they benefit the consumer?

Dolby TrueHD is designed to offer comprehensive metadata functionality similar to that found in Dolby Digital and Dolby Digital Plus. This includes downmixes that are defined by the content producer, dynamic range compression for late-night listening, and dialogue normalization to ensure consistent playback loudness between different content. For future content featuring discrete 7.1-channel playback, Dolby TrueHD also supports multiple
7.1 configurations, enabling the full creative possibilities of next-generation sound design to be delivered to the consumer environment."

Even Dolby TrueHD has Dialogue Normalization. I just wish the next generation A/V receiver can disable it. I mentioned before, my first DVD player - a Panasonic all-in-one DVD player/receiver, which has Dolby decoder only. It allowed me to turn on and off Dialogue Normalization. I don't know whether it was Panasonic's own feature, it sound great when its off.
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#17 of 119 OFFLINE   DaViD Boulet

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Posted August 02 2006 - 01:31 AM

Quote:
Now tell me, please, what does this Dialog Normalization does? I've seen Dial Norm on my encodings but never really used it. I'm a "the least processing the better" kind of guy. What does it do? Why do they use it? I know this is way too off-topic, would you reply me privately or suggest me to open another topic, please? Thank you.

It doesn't sound too bad at first... but how it gets the job done is the problem.

Dialogue normalization provides a way of "normalizing" the perceived level of spoken dialogue over mixed-source content... such as watching a TV show, then a commercial, then a movie... then a comercial. The idea was that you place a flag in the audio stream that describes the level (volume) of dialogue in comparison to a known marker, and then when all the various audio streams are played back one after the other the decoder could change level on the fly with each program to ensure that they all sound the same "loudness" so you wouldn't have to get up and down and mess with the volume or get blown out of your chair with a surprise loud-recording.

That's all fine and well when you're talking about media types like TV or cable where you stream together audio from many difference sources.

However, such a feature has no real relevance on a DVD where just a "movie" is presented... though I think that the application of audio commentary or documentaries might have been the justification in the minds of the folks at Dolby for setting the default value to a non-zero level (of course, one wonders what accuracy there could be in setting a default in an encoder without knowing the particular audio stream being recorded... duh? )

Here's the *problem* with dialog norm. It's *how* it goes about "normalizing". Basically, all Dolby decoders are REQUIRED by the spec to honor the dialog-norm flag and adjust level. Right there that's a problem... it can't be user-defeated (ie, there's no audiophile "bypass" the user could simply select).

Next, what the decoder does is after the DD compressed stream is extracted to LPCM, then the level/volume is *digitally* adjusted which recalculates the entire LPCM signal. Now, to many that may not sound like a big deal given the DSP many processors do to the original LPCM signal anyway. However, we're not talking about an advanced Lexicon algorithm... we're talking about a freebee digital-attenuation that comes with the Dolby Chip. And despite claims that such digital level adjustment is "transparent" one need only purchase an audiophile software application for the PC or MAC, feed in some bit-for-bit LPCM from some CDs and start to do listening tests to see what audible artifacts there may be from applying digital level adjustment. Bottom line for this listener is that I have yet to find an *audiophile* algorithm that can do this transparently... which gives me little confidence in Dolby's chip taking charge.

Basically 99% of the Dolby Digital DVDs on your shelf never let you hear the original extracted LPCM post decompression... they all have dialog normalization which forces the decoding chip to reprocess the signal yet again and digitally recalulate every single data-point.

Not good.

Back in the late 1990's I worked at a high-end AV shop called soundex and reps from Mark Levinson, Genesis, and others talked with us about the then-new audio comrpession formats like Dolby Digital. Their stance was that due to "degrading digital filters required in the signal path by design" that Dolby Digital could *never* be considered an audiophile way to encode regardless of how transparent the actual compression might become. Is that a clue?

And my little story still rings true... when listening to the Dolby Digital DEHT mix on the Lion King I was *struck* by how DTS-ish it sounded... bold, open, natural, complex tones, cohesive surround channels blah blah blah. When I got in touch with the audio engineer who mastered it and told him how the sound was so much better than the typical DD soundtrack to my ears and that it sounded more like DTS to me, he said "we didn't use any dialogue normalization". Again... he who has ears let him hear!

Dolby True HD will provide a bit-for-bit extraction from the packed audio data. HOWEVER, if dialogue normalization is applied to the mix, that bit-for-bit data will be lost completely as EVERY SINGLE DATA-POINT WILL BE RECALCULATED BY THE DIGITAL ATTENUATION ENGINE. In other words, Dialogue Normalized Dolby True HD won't be a bit-for-bit copy of the original... not at all.


Quote:
Even Dolby TrueHD has Dialogue Normalization. I just wish the next generation A/V receiver can disable it. I mentioned before, my first DVD player - a Panasonic all-in-one DVD player/receiver, which has Dolby decoder only. It allowed me to turn on and off Dialogue Normalization. I don't know whether it was Panasonic's own feature, it sound great when its off.

Wow. That's amazing. Technically that Panasonic was breaking spec with Dolby to give you that feature. I wish more manufacturers (especially audiophile ones) would have some courage and offer the same disable-feature to preserve the source LPCM data!
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#18 of 119 OFFLINE   RobertR

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Posted August 02 2006 - 02:19 AM

Quote:
all Dolby decoders are REQUIRED by the spec to honor the dialog-norm flag and adjust level. Right there that's a problem... it can't be user-defeated (ie, there's no audiophile "bypass" the user could simply select).
I don't think that's true, David. I know for a fact that my Denon AVP-8000 could defeat dialnorm (there was an explicit setting for this). Really, I think your opposition to dialnorm is excessive. All it does is change the level by 4 dB. That's not nearly the kind of "messing with the data" you imply.

#19 of 119 OFFLINE   DaViD Boulet

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Posted August 02 2006 - 03:18 AM

Robert,

I could have sworn that even Dressler stated that honoring the dialogue norm. flag was required by the Dolby spec.

Let's look into it. In any case, I'm thrilled that the Dennon allowed for it's defeat.

BTW, if you re-read my comments you'll see that I'm not complaining about the degree of volume attenuation... that's not the issue because the user can just adjust the primary volume to compenstate. The issue here is an added step of DSP that forces all the datapoints to be recaluclated so that you now longer have a bit-for-bit LPCM signal that mirrors what came out of the DD decoding engine. Any time you apply DSP and recalculate audio data you run the risk of degrading the sound, and so be design it's important that such 'features' be defeatable for audiophile applications.
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#20 of 119 OFFLINE   RobertR

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Posted August 02 2006 - 03:30 AM

Quote:
Any time you apply DSP and recalculate audio data you run the risk of degrading the sound, and so be design it's important that such 'features' be defeatable for audiophile applications.
I think that objection makes sense when talking about various processing modes such as "hall", "stadium", "theater", dynamic range compression, etc., but a simple change in volume doesn't really require a "guesstimate" of what the post-volume data should be, since it's a fixed, known amount. And since Dolby Digital can use 24 bit precision in making the change, and since we're not talking about a big volume change anyway, no meaningful bits are lost (It is IMPOSSIBLE to deliver 24 bit dynamic range or S/N in the home).


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