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  1. #1

    Does copying video files affect quality?

    I was recently making back ups of my files(including a lot of video) on my seagate external HDD and I was wondering whether the copying process will affect my files, particularly the video and sound files, in any way. How would I know if such a thing happened?


    Thanks in advance.
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  2. #2
    You're just copying the files, not re-rendering them. There should be little to no difference than the Original.
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  3. #3
    in fact there is a certain loss of quality, because during any moving process of data there could be that some bits may get switched. that can either cause decreased quality or even a corruption of the file so it's impossible to play it back at all.

    BUT!
    there are lots of coding technics to minimize these effects, like parity bits and multi-dimensional parity checks, just to name one of them.
    that way it is highly unlikly that there happens either loss of quality or even corruption, but there are still chances of it happening.


    just my 2 cents i got from my electrical engineering/IT courses :P

    edit:
    the above mentioned stuff only refers to the copying process and the file created through these means.
    the original file stays mostly unaffected as reading the source file is even less likely to get bits of the source switched, but again it happens once in a while, yet you won't notice it most of the time as there are mechanics that are able to fix it behind the scene in most cases.
    Last edited by Flaim; 2012-12-04 at 04:50 PM.

  4. #4
    you always lose data if you copy files ... a good way to imagine this is mp3s - before there were mp3s a much larger spectrum of sound waves was recorded - the reason (among other coding techniques) mp3 files are so small is because they only save what we can actually hear. now if you copy an mp3, and a certain note (it's more complicated but "note" suffices for this) is not copied correctly, the computer will look at preceding / following notes to correct the one it doesn't have. usually it's unnoticable though. all wired/wireless internet connections also lose data btw - and a lower signal (say 34% or w/e it says), while usually unnoticable, requires more data to be re-sent, but since it's very fast and the computer does that automatically you usually won't notice it

  5. #5
    Legendary! Granyala's Avatar
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    you always lose data if you copy files ... a good way to imagine this is mp3s
    W R O N G. You're describing rendering NOT copying.

    as long as the error correction of the file system can restore damaged bits there is 0 difference in content between the original and the copy.
    However if you have faulty hardware you can either get partially or totally corrupted streams which very well lost quality.

    Mostly this happens when using the Internet as data carrier, from HDD to HDD or Optical / Flash such uncorrectable error are pretty damn rare.

    Essentially: what Flaim said is true.

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  6. #6
    Quote Originally Posted by xindralol View Post
    you always lose data if you copy files ... a good way to imagine this is mp3s - before there were mp3s a much larger spectrum of sound waves was recorded - the reason (among other coding techniques) mp3 files are so small is because they only save what we can actually hear. now if you copy an mp3, and a certain note (it's more complicated but "note" suffices for this) is not copied correctly, the computer will look at preceding / following notes to correct the one it doesn't have. usually it's unnoticable though. all wired/wireless internet connections also lose data btw - and a lower signal (say 34% or w/e it says), while usually unnoticable, requires more data to be re-sent, but since it's very fast and the computer does that automatically you usually won't notice it
    While partially right, you're way off. MP3s are smaller than WAV files because that upper and lower sound is cut out... on purpose. It is done when making the MP3 in order to make it smaller, not as a byproduct of copying.

    As was said, any original and copied computer file should be identical, minus any potential corruption due to hardware failures. If you want to double check any files, just playing them will probably not reveal any corruption unless it is serious. Instead get software to create an MD5 sum or hash for each file and compare them.

  7. #7
    Quote Originally Posted by Granyala View Post
    W R O N G. You're describing rendering NOT copying.

    as long as the error correction of the file system can restore damaged bits there is 0 difference in content between the original and the copy.
    However if you have faulty hardware you can either get partially or totally corrupted streams which very well lost quality.

    Mostly this happens when using the Internet as data carrier, from HDD to HDD or Optical / Flash such uncorrectable error are pretty damn rare.

    Essentially: what Flaim said is true.
    If you read his post, he wasn't wrong.

    Either way, you can't render sound. You can only edit it.

  8. #8
    Quote Originally Posted by Diesta View Post
    If you read his post, he wasn't wrong.

    Either way, you can't render sound. You can only edit it.
    What he/she meant was that it equates to rendering. No change is made to the file when copied. If bits are lost, your computer automatically detects and corrects it behind the scenes. If something goes horribly wrong, you still have the original and can try the copy again.

    The poster wasn't flat out wrong about what they were talking about, but what they were talking about had nothing to do with what OP was asking.

    TLDR: You do not lose data when copying, only compressing/transcoding with certain formats.
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  9. #9
    Quote Originally Posted by Demoness View Post
    TLDR: You do not lose data when copying, only compressing/transcoding with certain formats.
    in most cases you're right, but as mentioned there are those rare occasions where either the source or the copy gets corrupted because of a few bits getting switched accidentally during the reading process, the data transfer or the writing process.
    even if you let a drive completely untouched it can be caused e.g. through cosmic radiation and the free ions it produces that are undloading the capacitors that are holding the information.

    but again, though such things are possible they are still extremely unlikely to happen.

  10. #10
    Quote Originally Posted by Flaim View Post
    in most cases you're right, but as mentioned there are those rare occasions where either the source or the copy gets corrupted because of a few bits getting switched accidentally during the reading process, the data transfer or the writing process.
    even if you let a drive completely untouched it can be caused e.g. through cosmic radiation and the free ions it produces that are undloading the capacitors that are holding the information.

    but again, though such things are possible they are still extremely unlikely to happen.
    Short answer: No

    Long answer: It's possible you and/or your hard drive might spontaneously combust

  11. #11
    Quote Originally Posted by The Cat View Post
    Short answer: No

    Long answer: It's possible you and/or your hard drive might spontaneously combust
    short answer: 0/10
    long answer: get your facts and sources straight before posting uneducated guesses

    read this and stop talking bull...
    Last edited by Flaim; 2012-12-04 at 05:25 PM.

  12. #12
    tl;dr:
    copying as in moving a file from your pc to the external hdd? in essence no.
    re-encoding video/audio? absolutely yes.

  13. #13
    Legendary! Granyala's Avatar
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    Either way, you can't render sound. You can only edit it.
    Sorry for the lack of precision in language, I used the term "render" as an analogy to "process".

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  14. #14
    I am Murloc! Xuvial's Avatar
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    Quote Originally Posted by Flaim View Post
    I think my brain jumped out of my head by the time I reached the 3rd page of that document O_O

  15. #15
    Quote Originally Posted by Flaim View Post
    short answer: 0/10
    long answer: get your facts and sources straight before posting uneducated guesses

    read this and stop talking bull...
    The thing is that all the errors you and other people are posting, can happen even if you are not moving your data...

    OP is not talking about data corruption that can happen 1/1000000... I bet he was asking about significant data/quality loss caused by copying files to a back up drive.

    OP as long as the original drive and the new drive are free of errors, your backup should be fine.

  16. #16
    Quote Originally Posted by Xuvial View Post
    I think my brain jumped out of my head by the time I reached the 3rd page of that document O_O
    and the relevant info starts on page 6 :P

    Quote Originally Posted by Moinaldo View Post
    The thing is that all the errors you and other people are posting, can happen even if you are not moving your data...

    OP is not talking about data corruption that can happen 1/1000000... I bet he was asking about significant data/quality loss caused by copying files to a back up drive.

    OP as long as the original drive and the new drive are free of errors, your backup should be fine.
    what i mentioned there is just one of the many sources for damaged source/backup files. the actual faulty transfer of the data i already mentioned in post #3
    Last edited by Flaim; 2012-12-04 at 07:29 PM.

  17. #17
    Dreadlord
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    Quote Originally Posted by Flaim View Post
    short answer: 0/10
    long answer: get your facts and sources straight before posting uneducated guesses

    read this and stop talking bull...
    Every answer on this thread which has claimed "yes" is essentially wrong.
    While it is remotely possible that a copy of a file will have something wrong with it, it is trivial to check if the copy is identical to the source.
    The link that this user posted does show that files can be degraded, but this goes for files on any media - including the original file being copied.

    Copying a file doesn't degrade the original.
    You can verify that the new copy of the file is the same as the original.
    The chance that the new copy isn't identical to the original is so slight that almost nobody does this check.

    I'm pretty sure that that sums it up for the OP, and provides the information that he wanted in the first place.
    All of the rest of this is grandstanding and showing off; the best answer for the OP is "NO".

  18. #18
    Quote Originally Posted by Moinaldo View Post

    OP is not talking about data corruption that can happen 1/1000000... I bet he was asking about significant data/quality loss caused by copying files to a back up drive.

    OP as long as the original drive and the new drive are free of errors, your backup should be fine.


    Quote Originally Posted by tyggyr View Post
    I'm pretty sure that that sums it up for the OP, and provides the information that he wanted in the first place.
    All of the rest of this is grandstanding and showing off; the best answer for the OP is "NO".
    Yup, I'm fine with those.

    Thanks for your time everyone, interesting posts though they were about way more specialized things than everyday backups.
    Quote Originally Posted by Bovinity Divinity View Post
    Then the [MMORPG] genre started attracting more players. These players wanted more of a "game" and less of a "world" [...]

  19. #19
    I am Murloc! Cyanotical's Avatar
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    you can lose bits when copying, however, the loss of a bit here or there will not affect sound quality, (unless you have ears like an elephant and are listening to the highest quality wave file)

    there are systems in place to prevent data loss and corruption when copying, however, these still lose a bit every now and then, but it's no different than what you lose by simply storing data, over time, HDD magnetic bits can grow weak, or SSD NAND gates can wear out, and you may lose a bit or two

    cosmic rays are not something i would worry about corrupting data, i'd be more worried about them giving you cancer, your computer has tons of shielding against cosmic rays and general EMI sources

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  20. #20
    No you won't lose any quality as far as I know.

    Copying means an exact full replica of the original.

    Quality and size will be the same as the original when the copying process is done.

    I'm assuming you're referring to simply copying and pasting.

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