Problems with Dolby EX

Discussion in 'AV Receivers' started by richRip, Jan 12, 2006.

  1. richRip

    richRip Auditioning

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    When I try to play SW III, only the opening THX logo scene is decoded by my receiver (Sony STR-DE995) as Dolby Digital 5.1 EX. The rest of the movie plays as regular Dolby Digital 5.1.

    In other words, when I have my receiver's surround back settings set to "auto" to decode the discrete back channel on EX produced tracks (rather than "matrix" which synthesizes the back channel), it will only play the discrete back channel during the THX logo, then no back channel during the movie. My receiver shows it is receiving an EX signal during the THX logo, but only regular DD 5.1 during the movie.

    This also happens on some other DVDs that are supposidely produced in 5.1 EX. Some DVDs with the EX logo do play correctly with the back discrete channel.

    Anyone else have the same problem?

    Could it be a problem with my Panasonic DVD player (can't remember the model #)?
     
  2. Dave Poehlman

    Dave Poehlman Producer

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    I don't have EX, but are you sure you don't have to go into the DVD's setup menu and choose the EX track?
     
  3. richRip

    richRip Auditioning

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    I've looked at that. SW III and most other DVDs don't have a separate 5.1 & 5.1 EX track, just one 5.1 EX track. Regular 5.1 decoders simply don't decode and play the back channels for 5.1 EX tracks.
     
  4. Michael Reuben

    Michael Reuben Studio Mogul

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    DD EX does not have a "discrete back channel". The center rear channel in DD EX is always matrix.

    I'm moving this to the Receivers forum (from Basics).

    M.
     
  5. richRip

    richRip Auditioning

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    It would appear from my users manual and from webopedia (see surround sound) that there is a discrete channel for EX or 6.1 surround. Maybe I don't fully understand the definition of the word "discrete."

    Anyway, it is clear that on EX produced DVDs there is a distinct track for the rear speaker(s). With the correct settings, my receiver (Sony STR-DE995) should decode that back channel on SW III and other EX-produced DVDs, but does not.

    There are also display icons that show whether the receiver is decoding a regular DD 5.1 signal or a DD 5.1 EX signal, and it shows the EX signal only through the THX logo, then starts decoding a regular 5.1 signal during the movie.
     
  6. John S

    John S Producer

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    It is a well known issue with the Star Wars III movie.


    You must turn it on... I typically just force mine to EX all the time though, no matter if it is really EX or not in all honesty, so I did not notice.


    But there was a thread about this a while back, so I went home and checked and sure enough the THX logo turns it on, but the movie does not. Even worse yet, the movie is really EX!!!
     
  7. Michael Reuben

    Michael Reuben Studio Mogul

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    Yes there is, but it's not encoded as a discrete channel.

    By way of comparison: In classic Dolby Surround, there are distinct tracks for the center and rear speakers, but there are only two discrete channels (left and right). The additional channels must be extracted by a matrix decoder. The same principle was applied to create DD EX from DD 5.1. As the Dolby site indicates, DD EX is still considered a 5.1 format, because the rear center channel is not discrete.

    M.
     
  8. richRip

    richRip Auditioning

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    Do you know in which forum this was discussed? I'd like to read what people said.
     
  9. richRip

    richRip Auditioning

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    On my decoder, there are 3 surround back settings: Auto, Matrix, and None. When "Matrix" is selected, it plays a back channel for both 5.1 and 5.1 EX DVDs. When "auto" is selected it plays (on most DVDs) a back channel for DVDs with 5.1 EX, but no back channel for DVDs with regular DD 5.1. "None," of course, plays no back sound for any format.

    What is the difference, do you think, of what plays with the "Matrix" setting and what plays with the "Auto" setting? If there is no difference, why the two settings, and why produce 5.1 EX DVDs when a decoder can play a back channel from regular 5.1 formats?

    I don't mean to argue, just understand. I've heard others say what you are saying before, but from everything I read, even from Dolby's site, it sounds like there is a discrete channel for EX. (But then again, why don't they just call it 6.1 instead of 5.1 EX?) Maybe you could post a white paper or something that explains this more.
     
  10. Michael Reuben

    Michael Reuben Studio Mogul

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    Any 2-channel mix can be run through a matrix decoder. But if that 2-channel mix wasn't created with a matrix encoder (as DD EX rear channels are), the result won't be what the sound designer intended. That doesn't necessarily mean it will sound bad, just different.

    M.
     
  11. Michael Reuben

    Michael Reuben Studio Mogul

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  12. richRip

    richRip Auditioning

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    I think what Lucas Online claims about purposely leaving out the flag is a bunch of BS. If they had purposely left out the EX flag, why did they put it in for the THX logo? Why did they encode the trilogy on DVD in EX?

    Stupid Lucas.
     
  13. Michael Reuben

    Michael Reuben Studio Mogul

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    If you set your receiver to "Matrix", you will get exactly what the sound designer intended, because the disc will play in DD EX, and that's the correct format for the Ep. III soundtrack. The "Matrix" setting won't get you what the sound designer intended on discs that do not have DD EX tracks.

    The one and only problem with the Ep. III soundtrack is that it doesn't contain the flag that's supposed to work with your receiver's "Auto" setting -- which brings us back to the simple instructions that John S gave in post #6 of this thread.

    As for the explanation from the DVD's producer (assuming it's genuine), who knows? There were various reports of incompatibilities when the DD EX flag was introduced; maybe someone was concerned about them, maybe not. It isn't really a big issue, once one correctly understands the EX format.

    M.
     
  14. richRip

    richRip Auditioning

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    Okay, I think I understand now. It sounds like the back channel in EX tracks is actually part of the surround channels; but when decoded correctly, it is pulled out of the surround channels to the back. When I have my receiver set to "Matrix," on a non-EX DVD, the receiver simply synthesizes or "guesses" on what to pull out to the back channel.

    So, I might as well leave my receiver set to "Matrix" no matter the format be 5.1 or 5.1 EX unless I get odd sound pulled back to the back speakers.

    (On a side note, I have a 5.1 DVD-A, "Tchaikovsky: 1812 Overture," that I like to listen to in the "Matrix" setting. That track sounds a lot better in 7.1 than 5.1, even though it is not produced in EX.)
     
  15. ChrisWiggles

    ChrisWiggles Producer

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    Yes. There really isn't any inherently fundamental difference between a 5.1 soundtrack and a 5.1EX soundtrack. They are both 5.1. One has just been monitored or mixed for playback with EX processing.
     

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