Copying and loss of quality

Discussion in 'Blu-ray & DVD Players & Recorders' started by Rico2, May 8, 2007.

  1. Rico2

    Rico2
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    Hi all. Just wondered whether anyone could clarify a point for me. I'd like to find out whether digital data degenerates with successive copying. The reason I ask is that I've copied footage from my camcorder to my Pioneer 433H - which I've then edited and burned to DVD. Very happy with the results and can't see any loss of quality at all.

    Ideally, I'd like to re-use the camcorder tapes. What I'd like to know therefore, is whether the DVD copy is effectively as high quality as the camcorder footage. If, for example, I copied the data from the DVD copy to the HDD, edited it, and copied it back to DVD - would I notice any loss of quality?

    Ta
     
  2. Gavtech

    Gavtech
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    The first thing I would want to say is - if you are happy with the end result -Why worry?
    But I daresay that your principle concern is rightly wishing to preserve original source material at the theoretical highest quality.

    Yes there is loss involved and how much it is will depend on how you handle it.

    The loss comes from encoding into the MPEG2 standard necessary for laying down onto a DVD.
    The encoding is done by the act of recording the material onto the HDD or a DVD.

    The most important principle of all in handling programme material is to keep the number of encodings down to a minimum, preferably no more than one, as each encoding throws more data away... and quality degenerates.

    Whether you can do this depends on the facilities of your DVDR. I don't know Pioneer machines in any detail, but they are usually very able machines.
    I am not sure if Pioneers support RAM disks [?] .. but if they do you can 'bounce' recordings endlessly and losslessly between RAM's and the hard disk as often as you like...and at high speed.

    If your machine will allow you to high speed copy to a DVD - That is lossless copying - because all that is happening is a digital clone of the original material is being made - ie No encoding.
    However, unless using RAM disks, you may be able to do this one way , but not the other... Were you to copy it back, you may have to do it in real time ... in which case that would be another encoding. Not desirable.
     
  3. maldonian

    maldonian
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    As a general rule (there may be exceptions but I'm not aware of them) if you copy DVD to HDD or HDD to DVD at normal speed the material is re-encoded and therefore deteriorates with each generation, but if you copy at high speed there is no re-encoding and successive generations are identical. When you copy from a camcorder the material is inevitably re-encoded when it's in a different format (but if it's a DVD camcorder you might be able to put the DVD into some recorders and make a high speed copy). The deterioration caused by re-encoding varies from imperceptible to very noticeable depending on the recording quality or mode you select.

    EDIT: oops - you beat me to it Gavin
     
  4. Rico2

    Rico2
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    Thanks - much appreciated. My machine does allow high speed copying. Am I right in thinking therefore, that although there will be some initial loss when the camcorder data is transferred to DVD, from then on, providing only high speed copies are made, there should be no loss of quality, no matter how many times the data is bounced back and forth so to speak?
     
  5. Gavtech

    Gavtech
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    Yes - That should be the case.
     
  6. Gavtech

    Gavtech
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    Hi Ian

    Two viewpoints are usually more useful than just one :)
     
  7. dvdope

    dvdope
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    sorry to hijack this but it has me slightly worried re mpgs saved on my comp. I have transferred lots of clips from vhs recorder tapes to my PC and saved them as MPEG. As i will need to back them up or copy them over to external hard drives will they lose quality each time i store them elsewhere? Being VHS originally the quality is hardly good in the first place and i thought once they were saved in MPEG they'd be perfect all the time regardless of copying them or saving them elsewhere.
    Should i be saving them in a different format than MPEG - AVI perhaps? TIA for any help at setting my mind at ease
     
  8. Gavtech

    Gavtech
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    No worries.

    Any loss was incurred in the original transcoding to MPEG... but once in that format you can file copy them endlessly without loss. [ I'm talking specifically about PC copying here which simply produces identical digital clones - No re-encoding involved ]

    Changing from one format to another almost invariably involves loss... so don't even think about transcoding to another format.
    There is nothing to be gained.
     
  9. dvdope

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    Phew! Thanks Gavtech :) Will copying the mpgs to dvd from the PC also be lossless?
     
  10. Gavtech

    Gavtech
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    Yes. :smashin:
     

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