Editorial: DVD, the X-Curve and Dirty Little Secrets

Discussion in 'Archived Threads 2001-2004' started by Vince Maskeeper, Jul 23, 2002.

  1. Vince Maskeeper

    Vince Maskeeper Producer

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    This is an issue I have wanted to talk about around these parts for a while. My first reaction was that this type of talk was best suited for the hardware section, but the more I considered it- the more I realized that this concept is old hat for many of the kids who hang in hardware - while the typical software junkie might have no knowledge of the whole issue.
    What's more, I didn't really know the best way to describe the situation and the potential problem as it exists currently, so I put off even discussing the issue. Today I happened across the DVDfile review of Blade 2 (located HERE.).
    Dan Ramer did such a great job of explaining the concept and setting up the dilemma, that I felt it would be best to simply quote his excellent assessment:
    Now this is something about which the average DVD junkie is largely unaware. I really think this issue is something that those of use who strive for the best possible presentation should be aware of- and make a priority...
    There are three issues in this passage quoted above that I would like to take a moment to address:
    1) Mr. Ramer states that there is one production house that removes the emphasis applied by the X-curve, Mi Casa (which is basically a project studio located in the home of Robert Margouleff). Now, while I'm certain Mr. Ramer didn't intend to do this, this might be read to mean that Mi Casa is the ONLY facility currently compensating for the X-curve on DVD mastering, and I'd don't believe this to be the case. In my own informal observation of DD soundtracks on DVD, I would say that a good percentage have been re-eq'd for DVD presentation (Maybe as high as 50/50).
    2) The X-Curve (aka wide-range curve) is the 3 dB per octave roll off starting at 2k in the theatrical playback system. This means the upper freq of a movie theater (and the monitors the films are mixed upon) are specifically lacking in high end freq- and as a result movie soundtracks are then mixed "hot" in the high freq to compensate what the monitors produce. If these soundtracks, intended for playback on an X-curve system, are played back on "flat" system like a Home Theater- they will seem excessively bright. Mr. Ramer again did a decent job of explaining this- however I wanted it to be clear that the curve is applied to theatrical systems, and thus result in soundtracks being mixed with excessive high freq information.
    3) This is the big issue for me: Mr. Ramer says that there is no practical way to currently determine if the material needs compensation or not, and alludes that the solution would be clearer information on the packaging. However what he doesn't seem to realize, and seemingly no one in the industry seems to utilize, is DD soundtracks have a specific flag in the header which explains the monitor type used in preperation of the soundtrack.
    This flag would be an absolutely perfect tool for improving the playback of DD soundtracks, if anyone would bother setting it from the default position! Processors could be easily designed to read the flag in the header and activate/deactivate theater compensation mode based upon the monitor type listed in the header.
    Much like the dreaded "dialog normalization" flag, which is quite possibly one of the best [but completely misunderstood] features of dolby digital encoding-- this monitor flag is going unused by the majority of people encoding soundtracks. This (like Dialog Norm) could be used to provide a better standard for DD playback, improving the image of DD as an encoding scheme and providing a better experience for all of us.
    In most cases, just like Dialog normalization- the flag is left at the default position on the majority of DD soundtracks.
    I think that it is important not only for DVD and HT enthusiasts to understand the role and concept of the X-curve, but to realize that the potential for enjoyment of DVD is often being sold short simply because the tools available are not being properly utilized.
    -Vince
     
  2. Kenneth Cummings

    Kenneth Cummings Supporting Actor

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    Thanks Vince, I was wondering about that X-Curve thing that DVDFile mention. Could that be why sometimes my DVD on my player sound a bit lower when other sound higher at times on the same setting?
     
  3. Vince Maskeeper

    Vince Maskeeper Producer

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    Could be- although this probably has to do with the overall encoding level on the various discs. Often the average overall level of audio material on DVD will differ from DVD to DVD- which is actually what dialog normalization was designed to correct!!

    The X-curve issue simply means that some DVDs will have excessive high freq signal (some discs will sound overly harsh) while others won't- and the main problem is that there is no real way to determine which is which...

    -Vince
     
  4. Jeff Kohn

    Jeff Kohn Supporting Actor

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    Vince,
    I agree with you this whole issue is very poorly documented/understood and needs improvement. I had heard that early DVD releases were almost always encoded for x-curve playback, but that newer releases were not. But I haven't heard any definitive information on how many current discs fall into either category.
    The approach I tend to take is to keep cinema-eq off, and only turn it on for meterial that seems excessively bright or harsh. But I agree it would be much better if the processor could read a flag to determine which mode to use automatically.
     
  5. Aaron Garman

    Aaron Garman Second Unit

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    Hello all. I like what you had to say Vince. But I do have a few questions regarding other 5.1 systems. First, does DTS use this same type of technology or is it merely a Dolby Digital thing. Also, when Laserdiscs had 5.1 Dolby Digital tracks, weren't they just the actual theatrical tracks, and not re-mixed for home theatres? I was always curious because many times Dolby Digital sounds better on Laserdisc than DVD. My favorite example is Mission: Impossible. For some reason, everything has more clarity. What do you all think?

    Aaron Garman
     
  6. Dan Ramer

    Dan Ramer Agent

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    Vince, thanks for highlighting an issue I feel needs industry attention, and thanks for adding further clarity to a system I had to express in the simplest and briefest possible terms within a DVD review. A few comments...

    When I cited Mi Casa, I did not mean to imply that it was the only shop that removes pre-emphasis (see below). It was in the context of my review of Blade II; Mi Casa did that audio.

    You are, of course, quite right about the possibility of inserting another flag in the MPEG-2 bit stream. I don't think I wrote that there is no practical way to solve this problem; I simply said that there is no existing standard. I suspect that by the time the existing DVD standard could be modified and approved by the consortium, and by the time decoder manufacturers respond with new product, it might be years. Until such an action is taken, I'd like to see a short term solution implemented immediately. Hell, I'd like to see the studios publish a list of their existing titles on there web sites to specify which DVDs have the X-Curve intact. How else can we deal with our existing collections?

    Jeff, I performed an interesting experiment a year or so ago. I have a large collection of film scores on CD, and I'm unaware of any for which the X-Curve was left intact. So I put together as many DVDs as I could that had either opening or closing credit music unencumbered by dialog or sound effects for which I also owned the CD. I first synchronized playback and switched back and forth to ensure that the CD was derived from the theatrical mix (for example, the original E.T. CD was predominantly recorded for the score release and is different from the theatrical tracks, which were released years later on a special CD). I then did a long term spectral average of appropriate and identical music from the CD and the DVD and subtracted one spectrum from the other. For about 50% of the comparisons, I found a rising response on the DVD, indicating an intact X-Curve. There was no correlation with regard to studio, release date, audio format... it seemed quite random, even within a specific studio's output.

    Aaron, the pre-emphasis is found in the theatrical mix; it's independent of the encoding system, so you're just as likely to listen with the wrong spectral balance in DTS as in DD.

    Dan
     
  7. Brendon

    Brendon Second Unit

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    Interesting conversation, one I've given some thought to myself over the years.

    I can only think of once or twice (the remaster 2 disc set of Se7en being one) where the packaging states that no re-eq needs to be applied - the soundtrack has already been adjusted for home playback.

    otherwise, as has been mentioned, there is no way to determine if re-eq should be applied to a given soundtrack, other than it sounding "too harsh" when listening to it. (I can only think of one or two discs where I have found the soundtrack too harsh right out of the gate - The Straight Story and Monsoon Wedding. Others sounded harsh after protracted listening).

    I am curious however just how many people have re-eq in their processors arsenal to make use of any information the studios may put out. Whilst many of us have some form of THX post processing, most do not. I know that Onkyo have sometimes implemented the re-eq aspect of THX pp, others their own form of re-eq.

    The only other issue I have with THX pp is that it is an all or nothing package. Re-eq cannot be applied whlist suppressing Timbre matching, or (Adaptive) Decorrelation.

    Perhaps, given the calibre of your average web reviewer's setup, reviews could feature whether re-eq is needed for a given disc. (Obi's review of Close Encounters did, and advocated the use of THX pp if you had it).

    Looking forward on reading the rest of this thread!

    Cheers,

    Brendon
     
  8. Jack Briggs

    Jack Briggs Executive Producer

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    This goes back to the very essence of what can be determined as "high fidelity" as opposed to the euphonic "high distortion" so many seem to prefer. When I was reading the above, I kept thinking of the old RIAA equalization errors that used to plague me as an enthusiast of "high end" audio.

    Recording engineers are now contouring the audio of DVDs to mimic the sound of audio as reproduced in commercial cinemas.

    Isn't faithfulness to the original soundtrack, be it two-channel audio only or a 5.1- (or more)channel film soundtrack on DVD? But, then, what is an "accurate" movie soundtrack? The sonics in soundtracks are more processed than Kraft Cheese, no matter how thrilling they may sound.
     
  9. Vince Maskeeper

    Vince Maskeeper Producer

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    Many products, even non-THX have some sort of cinema re-eq. My last Denon receiver had one, and my outlaw 950 has one- non-THX cinema RE-Eq. I don't know how common it is, but I imagine that most respected processors and receivers offer it...
    -Vince
     
  10. Dan Lindley

    Dan Lindley Second Unit

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    My Onkyo 575x has "Cinema re-EQ," and this is frustrating to learn that some DVDs need it and others may not, and there is no way to tell the difference. I have just left it on on the assumption that there was a standard standard.

    Dan
     
  11. Dan Ramer

    Dan Ramer Agent

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    Vince,

    I was unaware that a large room / small room flag already exists within the DD bit stream. That makes this situation even more frustrating.

    I'd like to know which production houses (if any) are setting that flag correctly, and which (if any) decoder manufacturers are responding to it.

    Dan
     
  12. Daryl L

    Daryl L Supporting Actor

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    This is really interesting. So I went looking for info. Here's a quote from SMR.
    This quote came from the last sentence on the link above.
     
  13. Daryl L

    Daryl L Supporting Actor

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    I E-mailed Mi Casa Mulitimedia yesterday and I just got a reply back from Robert Margouleff.
    First quote is my question. Second quote is his reply.
     
  14. Dan Brecher

    Dan Brecher Producer

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    Mi Casa did Fellowship of the Ring, and it's by far the best audio master for a DVD I have ever heard. The expansive soundstage, the depth and the detail is just astonishing...

    Dan
     
  15. Dan Ramer

    Dan Ramer Agent

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    Daryl,

    Thanks for directing my attention to the Mi Casa list of de-emphasized DVDs.

    That was helpful, but we need so much more information. Within the 597 DVDs in my collection, I found only 16 titles on their lists for which the X-Curve had been equalized away (and that includes two titles I have on order).

    I think the studios really need to address this problem.

    Dan
     
  16. Daryl L

    Daryl L Supporting Actor

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    Dan Ramer,
    597 dvd's? Geeeeeeeez dude! That's alot. Well my measly collection only consists of 76 dvd's(not counting individual discs in box sets) and 2 more on preorder and I only found 4 of mine listed on the Mi Casa site. [​IMG]
    Granted this info isn't no where near enough but it's a start and I think a big Thanks should go to Mi Casa Multimedia just for taking into account the X-Curve and Home Theater Enthusiasts during their mixing. Atleast they did the de-emphasizing and put the info out their to be found. Just had to dig alittle. Maybe this thread can help make some changes elsewhere. Because with my AVR8000 if I need to apply Re-Eq I must turn THX processing on which I'd prefer not to do. [​IMG]
     
  17. Chad R

    Chad R Cinematographer

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    Fascinating read. It's an issue I have been aware of before after reading WSR article on Mi Casa. Since then I have turned THX off on their discs if I could tell it was one of theirs.

    The problem for me now becomes THX discs. It has been asserted in the past that THX discs will not employ any re-eq as they expect their processors to do it on our end. However, Mi Casa lists "From Hell" as one of their titles, and it bears the THX symbol.

    Confusing. There should absolutely be some type of quick note on the packaging telling us if the disc needs re-eq or not.
     
  18. Dan Ramer

    Dan Ramer Agent

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    Daryl,

    It does help to be a reviewer. :b

    Dan
     
  19. Wayne Bundrick

    Wayne Bundrick Cinematographer

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    Maybe my point of view is bass-ackwards but I think neither Mi Casa nor anybody else should be making it their business to f*** with the equalization on a theatrical soundtrack. I don't want a soundtrack that's been watered down for home consumption, I want the theatrical soundtrack without alteration.
     
  20. Dan Ramer

    Dan Ramer Agent

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    Wayne,

    The unfortunate truth is that a film soundtrack with the X-Curve pre-emphasis intact is presented inaccurately in the home theater. It's too bright. The high frequencies are exaggerated. What Mi Casa or THX Re-equalization does is correct a frequency response problem so that the home theater experience is as close to the theatrical experience as possible. When I find some time, I'll try to locate an in-depth technical paper or two on the web and post the link(s). In the mean time, you might want to explore the Mi Casa web sight; I'd expect such a paper to be there.

    Dan
     

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