DVD Layer Change

Discussion in 'Archived Threads 2001-2004' started by SamC, Jan 31, 2002.

  1. SamC

    SamC Agent

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    I currently have a Toshiba DVD player (SD1200 I think). I bought it about 12 months ago, after my first DVD player which was a JVC that I had for about 18 months before that.

    I know that there is a layer change, and we all cringe when it happens, but which machines are best at minimising the effect of it??

    Is there a DVD player on the market (or one that someone know is in development) that has a cache memnory to buffer the info and prevent the layer change being apparent?? I guess this would be similar to a portable CD player's buffer.
     
  2. Nikos

    Nikos Auditioning

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    I recently read that the layer changes are noticed because the software (DVDs) are dumping their cache and switching layers. Some DVD players perform this task quicker than others (ie Denons) but there will ALWAYS be some sort of noticeable pause if the software was designed that way.

    There are some DVD titles (I'm not sure which ones) that offer seamless layer changes and from my understanding, just about all DVD players are able to perform that.

    Nikos
     
  3. Chuck C

    Chuck C Cinematographer

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  4. Ken Seeber

    Ken Seeber Supporting Actor

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    Several Denon DVD players have 4 megabyte memory buffers to eliminate this problem.
     
  5. AbelM

    AbelM Second Unit

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    Really I have Tosh SD1700 and I can't tell the layer change ona few DVD's...

    Driven

    Remember the Titans

    Fifth Element

    T2

    Saving Silverman

    Freddy Got Fingered

    The Original Kings of Comedy
     
  6. John Kotches

    John Kotches Cinematographer

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    All,

    Let's get something clear. Every disc that is dual layer, must have a layer change. There are two ways to encode them:

    Non-seamless -- this is the DVD specification.

    Seamless -- technically outside of DVD specification.

    There was discussion earlier about buffers and dumping/etc.

    Non-seamless layer breaks force a buffer dump, which means you have to seek to the new position and refocus. For RSDL encoded, this means just a refocus -- for Dual Layer non Reverse Spiral, you have to seek back to the beginning of the disc and refocus.

    Sony Superbit discs are encoded seamless layer break, and on the players I've worked with (Onkyo DV-S939/Toshiba SD-9200, JVC XV-SA75GD, Toshiba SD-5700, Kenwood DV-5700, Panasonic RP-91N) all have handled this flawlessly.

    DVD-ROM drives generally do better on layer breaks than standard mechanisms, and the best layer changes we've measured utilize DVD-ROM drives (Denon 2800, approximately 0.25 seconds). We time this using a specific title (the WHQL disc layer change). It is an excellent benchmark, as the chapter and time are clearly noted, and the content is ideal for observing the break.

    Regards,
     
  7. Ken Seeber

    Ken Seeber Supporting Actor

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  8. John Kotches

    John Kotches Cinematographer

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    Ken,
    True that during this particular film playback there is not a layer change. Should I amend my point for discs where the films that have layer breaks within the film?
    This doesn't change the point of the argument anyway [​IMG]
    Regards,
     
  9. Adam Barratt

    Adam Barratt Cinematographer

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    Excluding SuperBit titles, virtually every RSDL DVD I have seen for the last two years has included a visible layer-change.

    However, several older discs such as Blade and Lost in Space have completely seamless layer switches (occurring mid-scene during on-screen movement and even dialogue; not simply masked by static scenes or fadeouts as in T2 or Apollo 13).

    Dragonheart, an even earlier title (released nearly four years ago), also has a completely seamless layer change, so the ability has been present for a very long time. Why these types of invisible layer-changes aren't more common is a mystery.

    Adam
     
  10. RichardH

    RichardH Supporting Actor

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    So, technically, how does the seemless layer change work?
     
  11. John Kotches

    John Kotches Cinematographer

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    I'm not certain of the mechanism, but imagine it's a flag in the metadata, indicating either Seamless or Non-Seamless layer break.

    With a seamless break, the buffers aren't dumped, so you don't have the pause to dump/reload the buffers.

    Regards,
     
  12. Adam Barratt

    Adam Barratt Cinematographer

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    I'd also be curious to know the exact process if anyone knows. I'm guessing it involves a low movement segment that reqires only a minimal datarate being 'pre-loaded' into the buffer; the full buffer then plays back this information while the laser re-tracks. Anyone know for sure?

    Adam
     
  13. John Kotches

    John Kotches Cinematographer

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    Matthew,

    The location of the layer change is a function of data rate. So they could have changed the location of it by changing the data rate.

    I agree, that's a crappy spot for a layer change, and I'm surprised this wasn't caught in the test pressing.

    Regards,
     
  14. Larry_W

    Larry_W Agent

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    I have a Pioneer DV-434 and the layer change is very noticeable on this and on the older 425 (i think that's the model #). I'll probably upgrade one of these days...after the SVS and TV.
     

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