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What is layer change?

Discussion in 'Blu-ray & DVD Players & Recorders' started by Gadjet, Jul 29, 2002.

  1. Gadjet

    Gadjet
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    I am buying the Pioneer 747, after reading thread sent in by Duncan Harvey and the response that he has had saying it has slow layer change.
    Could you please tell me what this means? And how will this will effect picture quality on the player.
    I choose this after reading the review in Home Cinema and it being their mumber one choice, why do they give out this advice if the player is not that good. This maybe way out but do they get commision on saying how good a company,s product is when it isn,t?
    Now even though it is on order I am a bit worried I have bought the wrong one, £700 is a lot of money to me and it has took a lot of reading to decide.
    Your views will be well appreciated.
    Phill:(
     
  2. Zacabeb

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    DVD's can have two layers, one is semi-transparent and the laser can read either one by focusing differently. This nearly doubles the storage capacity, from 4.7 to 8.5 GB. That means it is commonly used for DVD Video.

    When the end of the first layer is reached, the player must switch to the other layer to continue playing. Depending on how fast the drive can do this and how much read-ahead cache is in the DVD player, this may cause a delay in audio and video, making the player freeze for a split second. This can often be noticable and annoying. I think some AV hardware may lose sound for a few seconds even during layer changes.

    The layer change will only happen at a single point in the movie, but if you are watching some weird multi-angle director's cut bonus version found in the special features on a DVD, the speed of the layer change and access speed of the drive may also have an effect.

    Usually the layer change is put in a suitable cut, like the reel changes in the cinema. The speed of the layer change may vary between different discs of the same title as the layers may be rotated differently relative to one another, and from time to time depending on all sorts of real-world factors.
     
  3. Squirrel God

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    Not always :(

    Donnie Darko R1 has TWO layer changes. It switches from Layer 0 to Layer 1 at the end of Chapter 21 so that it can play Chapter 22. After it has played Chapter 22, it switches back to Layer 0 to play Chapters 23 onwards.

    However, this is the only disk with more than one layer change that I have come across -- thankfully! :)
     
  4. Reiner

    Reiner
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    Donnie Darko R1 has TWO layer changes. It switches from Layer 0 to Layer 1 at the end of Chapter 21 so that it can play Chapter 22. After it has played Chapter 22, it switches back to Layer 0 to play Chapters 23 onwards.

    Not to insult your intelligence and knowledge, but how do you know that?

    As the discs are RDSL I just cannot imagine that you can have more than one layer change - and I don't see why this is necessary?
     
  5. Guest

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    Reiner

    Donnie Darko does have two layer changes.... it switches once and then goes back to the original layer. I don't have the disc myself but have read this elsewhere... the layer change symbol on the player's display distinctly flashes twice.

    Gadjet

    Let me get this right £700 is a lot of money for you to spend on a DVD player and yet you base your decision solely on one magazine review?! Pioneer players (I have the 545) are generally thought to have slow layer changes but I have to say that I have seen much much slower. Like Zacabeb says in the majority of cases layer changes are positioned so as not to be that noticable ie. when one scene cuts to another or during a fade to black and until recently I had not noticed a single change on my player. However when changes happen in the middle of a scene when dialogue and incidental music is present they are very noticable and IMHO very annoying. Denon players are the only ones to include a 4mb memory buffer which minimises the problem or gets rid of it altogether.
     
  6. Reiner

    Reiner
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    ... the layer change symbol on the player's display distinctly flashes twice/

    Uh, never heard of that feature ... damnd, I must update my Bio-RAM immediately! :)
     
  7. Squirrel God

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    It confused the hell out of me at first as well - I thought I had a faulty disk or there was a glitch in the master encoding of the disk! But I investigated it further and the two layer changes on this disk have been widely reported on US DVD forums and elsewhere, as James says.

    Some players (particularly older Sony players) appear to have an on-screen layer change indicator (icon) to show when a layer change occurs on a disk - those using such players have also confirmed that Donnie Darko has two layer changes. On my own Sony player, its confirmed by the usual indicators of layer changes (flashing of the pause symbol together with a flickering change in display from "Dolby Digital 3/2.1" to just "Dolby Digital" and then back to "Dolby Digital 3/2.1" again).

    The only reason I can think of for having two layer changes with this disk is because the arrangement of the cells on the disk had to be "just so" in order to cram all the data onto this disk. It is, after all, jam packed with special features, including lots and lots of deleted scenes. Other than that, I can only think that it is a bad design.

    Thankfully, the two layer changes couldn't be in better places so they are not disruptive.
     
  8. Pete Callan

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    I originally thought layer changes must be something really serious the way so many people go on about them.

    They're really no big deal - my Tosh 510 has layer changes every now and then whilst watching a film but its never bothered me one bit; chill out everyone!
     
  9. Squirrel God

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    In most cases, I would agree with you. :)

    But some disks just have the most ridiculous layer change points. For example, There's Something About Mary R4 has a layer change in the middle of the scene where Ben Stiller has been arrested for the "events" in the bushes. When I say "in the middle", what I mean is - the layer change occurs as he pauses for breath mid-conversation :eek: In my book, that's just plain silly.
     
  10. Reiner

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    Agree, nothing really serious but annoying from time to time, especially if the change is placed in the middle of a scene as Squirrel God describes. Does happen on quite a few discs.

    My old player used to jump to the next chapter once in a while during the layer change, and it took me a while to figure that I just missed a few scenes!

    Thanks for the clarification Squirrel and James. Anywhere I can find some technical details about that?
    Not that I don't believe you (I do!) but I am interested in how that works ...
     
  11. Squirrel God

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    None that I've found, other than user's posts on forums. A typical example is this US forum thread:
    http://www.dvdtalk.com/forum/showthread.php?s=&threadid=193730

    If you want details of the DVD spec, in terms of the physical and logical data structure, then you can check the links that I and others posted here:
    http://www.avforums.com/frame.html?...s.com/forums/showthread.php?s=&threadid=41168[/url]

    At the end of the day, a DVD is, in essence, nothing more than somewhere to store data, so it's very much like a hard disk or CD-ROM (you could say that Donnie Darko needs to be defragmented :)). In fact, DVD-ROM is the base standard on which DVD-Video and DVD-Audio are built. The data is not always continuous and can be stored on any of the two layers in whatever order you like (as long as the data structure is obeyed). It's just that, to prevent delays, DVD-Video is usually designed so that the data is continuous. When seamless branching is used (e.g. T2) the data is not continuous on the disk, but it appears to be.

    I have been looking for some software on the web that will show me exactly which bits of the DVD (including which layers) are being accessed at which time but I have yet to find any. :(
     
  12. knoddie

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    If you're worried about one or two layer changes, how about this?

    Having a problem playing certain DVD's. These are rentals. They're found in the weekly section, are double sided discs (you have to turn the disc over half way through the movie), are normally releases of pretty old films, don't have printing on the CD other than a small yellow area near the hole. (by the way, I'm in Australia)

    The prob is that the movie pauses for a couple of seconds between each scene. Means there's a pause every couple of minutes.

    Had this problem with two DVD's now...Evita and The Right Stuff.

    Normal DVD's (recent releases, double density etc) play perfectly.

    Any ideas??
     
  13. Guest

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    the 'flipper' discs you mention were kind of common a few years ago. Discs like Goodfellas being an example (thank god for the forthcoming SE!), but I don't know what could be causing the pauses between scenes, sorry.
     

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