Digital Video Archival Format?

Discussion in 'Digital Video' started by AtHomeBoy_2000, Nov 11, 2008.

  1. AtHomeBoy_2000 macrumors 6502a

    AtHomeBoy_2000

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    #1
    I work for a church and we have BOXES of old VHS tapes. Many of them have content I'd like to preserve for the future.... a future where VHS will be extinct to the average consumer. So, over the next year I'd like to begin the process of archiving these tapes into a digital format on a series of external hard drives. I figured a few terabite drives should work fine... but what format should the video be stored in? I was leaning towards using DV since that is a fairly universal format. I dont want to compress the video. Are there other, better, options? Any suggestions?
     
  2. -DH macrumors 65816

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    #2
    DV would probably be the best format to store on hard drive, as it takes relative little space (13.3gb/hour) for the quality offered, plus it only has a mild 5:1 compression. And with the price of hard drive storage space dropping all the time, you could set up a mirrored RAID for added protection.

    Here's an example of inexpensive hard drives (10 cents per gb): http://dealmac.com/Seagate-1-5-TB-S...g-more/260137.html?redir=1&ref=alert_bottom_1

    You might also want to consider transferring the VHS originals to DV tape.

    -DH
     
  3. MisterMe macrumors G4

    MisterMe

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    #3
    The OP can do much better than that. You are considering the storage requirements for DV at DV resolution. The data rate of VHS is much less. At its best, it is equivalent to a 320x240 QuickTime video.
     
  4. LethalWolfe macrumors G3

    LethalWolfe

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    #4
    DV is far from ideal, but it's the most cost effective for a consumer. I'd suggest recording to MiniDV tape as well. Most cameras allow you to record to tape and record to the computer at the same time. Make sure to use s-video and not composite so you can get as clean a capture as possible.

    While you are correct that, in digital terms, VHS can resolve about 320 horizontal pixels of information that 320 pixels worth of info is spread out across 720 pixels. So if you only capture at 320 you'll be tossing away about half of your picture information.


    Lethal
     
  5. -DH macrumors 65816

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    #5
    WTF? VHS doesn't have a data rate. It's an analog format. It won't have a data rate until it's digitized ... and at that point, it is no longer VHS.

    Where do you get your information?

    -DH
     
  6. MisterMe macrumors G4

    MisterMe

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    #6
    Analog data is still data :rolleyes:
     
  7. Le Big Mac macrumors 68020

    Le Big Mac

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    #7
    If it's being archived for later use, why not just get it transfered to MiniDV and leave it at that? When needed for use, you can import it onto a computer for editing. But why buy a bunch of hard disks as well just to store it for the time being?
     
  8. -DH macrumors 65816

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    #8
    Once the analog signal is converted to a data stream, it IS NO LONGER VHS; it's whatever it has been converted to. VHS has no data rate. Roll your eyes alll you want, it still won't have a data rate.

    -DH
     
  9. ftaok macrumors 603

    ftaok

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    #9
    Very few miniDV camcorders have s-video inputs anymore. Some don't even do the A/D conversion either. If you want to archive to miniDV tape as well and want max quality, look for an older miniDV camcorder.

    If you don't want/need the miniDV tape as an archive, a Canopus 110 would be a good investment as it has s-video inputs.

    Of course, this could all be moot if the OP doesn't have (or have access to) a VHS deck with s-video.

    ft
     
  10. Le Big Mac macrumors 68020

    Le Big Mac

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    #10
    If it's a lot of tapes, it may be more cost-effective to pay someone to do it with a professional set of equipment.
     
  11. Cromulent macrumors 603

    Cromulent

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    #11
    Of course it does. It is just measured in a different way to digital data. It is measured using Hz as it is an analogue wave form. In much the same way as terrestrial radio.
     
  12. -DH macrumors 65816

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    #12

    OK then, what IS the data rate of VHS?

    My point is that, in the context of this discussion, an analog signal does NOT have a data rate. It may have bandwidth and carrier frequency requirements for pass through, it may have a signal-to-noise ratio, but it does NOT have a data rate.

    Now if you want to insist that analog data has a data rate and that a stack of reports printed on paper can be considered "data," what's the data rate of the stack of papers?

    -DH
     
  13. MisterMe macrumors G4

    MisterMe

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    #13
    Here is an excellent piece on the subject. You may scream, rant, and rave all you want.
     
  14. -DH macrumors 65816

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    #14
    Thanks for the link to the article. Nowhere in that article does it state a data rate for VHS or claim that it even has one. Thanks again for proving my point.

    And once again I'll state my point: VHS, like other analog formats has no data rate for the purposes of this discussion. But once the analog signal (whatever it's source may be) is converted into a digital signal, it definitely does. But what that data rate will be can only be determined by the digital format it's converted to.

    For example, if it's converted to DV, the data rate will be 3.75mbps.
    For DVCPro 50: 7.5mpbs
    For Uncompressed 8 bit: 20.2mbps
    For Uncompressed 10 bit: 27.65mbps
    For ProRes 422: 5.5mbps
    For ProRes 422 HQ: 8.0mbps

    -DH

    ps; I'm not screaming, ranting or raving ... just trying to dispel the misinformation presented in this thread.
     
  15. ChrisA macrumors G4

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    #15
    You are correct "data rate" does not apply to VHS. I think, maybe what he means is "bandwidth". VHS can have up to about 6 MHz of bandwidth but more likely less than 4 MHz.

    Technically speaking "data rate" is rather imprecise and not even a valid unit of measure. I think "Data rate" is a generic term like "length". There are units of length (such as foot, meter or mile) but "length" itself is not a unit. Data rate is a generic term for units such as "bits per second" or "bytes per second". These are all some quantity of data over time. The problem is the VHS is not digital data. There are not bits or bytes. VHS does have frames, fields and scan lines and we can talk about how many of those happen per second (The answer would depend of if the tape were NSTC or PAL.)

    When you choose an archive format you want one that will capture ALL the detail on the tape. DV is good at this. Also you want an archive format that will not add any of it's own artifacts to the image. Again DV is good at this.

    Also you have to look at the intended use of the archive. Will you want to at some later date edit video or will it only be watched as-is. If the latter DVD is ideal as there are likely to be DVD players around for a long time. But DVD is a poor choise it you want to edit the video. For that DV is good.

    No archive format will last forever. Eventually any format will become un-readable. You will need to re-write the archive periodically

    And next we can talk about backups. You will need to make several copies and spread them around.
     
  16. MisterMe macrumors G4

    MisterMe

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    #16
    I see that you are one of those people who likes to play with numbers unrelated to their underlying meaning. This thread was supposed to be about archiving video. My original response to you was intended to give you an idea of how much space would be required. My assertion that a 320x240 QuickTime movie would do the job was certainly in the ballpark.

    You wanted to archive to a hard drive. A QuickTime video fills the bill in spades. Any format with significantly higher resolution merely oversamples your video with no significant improvement in the quality of your archives.

    You've gone all around Job's barn trying to avoid learning something. The bottom line is that QuickTime videos remain your best bet.
     
  17. LethalWolfe macrumors G3

    LethalWolfe

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    #17
    As I said in my previous post a 320x240 QuickTime would cut in half the already low quality VHS image. NTSC VHS may only contain 250 lines of information but those 250 lines are interpolated across the 520 visible lines of the NTSC standard.

    Also, I think you meant to use the term "upsampling" or "upscaling" not "oversampling." Going from SD to HD is an example of upsampling while going from HD to SD would be an example of oversampling.


    Lethal

    EDIT: Also, QuickTime is just a wrapper, not a codec. Anything from uncompressed HD to low-rez web video can be a QT file.
     
  18. KeithPratt macrumors 6502a

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    #18
    And DV is a lot simpler. If the OP has a lot of tapes it makes sense to keep it to as few steps as possible. It's also handy for a painless transfer to DVD, should that ever be desired.
     
  19. MisterMe macrumors G4

    MisterMe

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    #19
    Oversampling means to record data to a precision higher than that of the underlying system. Oversampling is a general measurement issue, not just an issue of recording video. Upscaling is used only in the context of video. It is a different issue.

    If you go back and read the link in my previous post, then you will see that VHS is listed as having 330 x 480 effective pixels giving 250 lines of resolution. However, long before the advent of digital video, the resolution of video was an issue. I have never seen anyone claim that VHS recorded 250 lines of resolution in the real world. The numbers I've seen are more like 220.

    QuickTime is a container and not a codec? Well actually, QuickTime is the audio-visual frameworks of MacOS X. More to the point, QuickTime is the most convenient tool to get the job done for the OP. Standard QuickTime codecs include .mp4 and H.264. H.264 is now the default. The OP may use whichever codec he wants.
     
  20. LethalWolfe macrumors G3

    LethalWolfe

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    #20
    We are in a video forum talking about video. I think it's safe to assume that terminology used here is being used as it relates to video. For example, if someone is talking about 'grading' in here I doubt they are talking about evaluating term papers but about color correcting a video image. Yes, oversampling and upscaling *are* different and the term you should've used was upscaling (or upconverting, or upsampling). A working example of oversampling is the RED One camera. Here is a link to brief discussion along these lines at DVinfo.net.

    Now who likes playing w/numbers? ;)Whether VHS can effectively resolve 220 or 250 lines is beside the point. The point is that VHS conforms to NTSC standards 525 lines, 29.97fps, etc. (or PAL standards where appropriate). I think the disconnect happening here is that there is a difference between the detail a given format or camera can resolve and the resolution of the standard that format or camera adheres to. For example, a $20K DV camera can resolve more detail than a $500 DV camera even though they both record at 720x480. A VHS VCR kicks out a 525 line signal even though the image quality of that signal is measured at only 200-some-odd lines.

    I'm not sure why you are getting so defensive but telling someone that "A QuickTime video fills the bill in spades" and "The bottom line is that QuickTime videos remain your best bet" is too vague to be of any real help. A QT movie can be one of a hundred different things. It's a common error for people to talk about QT as if it were a codec and I'm just trying to help you so you can better help yourself and others. H.264 can be a great codec for final delivery/viewing but it's not a good codec to use to archive material (an exception could be if we were talking about a High Profile AVC-Intra version of h.264 but I think that's beyond the scope of this thread).


    Lethal
     
  21. MisterMe macrumors G4

    MisterMe

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    #21
    The OP in this thread is not about finding the best tape format to replace VHS, broadcasting the videos, or anything of that sort. It is about archiving aging VHS tapes on a computer hard drive. To do the job, the OP needs a file format that preserves the full fidelity of the source material in the minimum file sizes. The DV tape formats are massive overkill.
     
  22. LethalWolfe macrumors G3

    LethalWolfe

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    #22
    A file format that preserves the full fidelity of the source would be uncompressed SD or Apple ProRes SD (ProRes is a 'visually lossless' codec). DV will apply its lossy, 5:1 image compression and 4:1:1 color subsambling to the VHS signal and actually result in an inferior image compared to what's on the VHS tape. But going VHS->Uncompressed SD isn't really a viable option for the OP where as going VHS->DV is. DVCPro 50 would be a good compromise between file size and image quality, but that would require additional hardware costs that the OP probably doesn't want to incur. DV isn't great (it's one step above DVD which is one step above VHS), but it's the best consumer SD format out there so why wouldn't one pick the best format one could afford when making archival masters?


    Lethal
     

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