Canon 5D MarkII: Why compression?

Discussion in 'Digital Photography' started by MBX, Sep 28, 2008.

  1. MBX macrumors 65816

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    #1
    Is there a reason why they're using the h.264 for video compression or why couldn't they offer a uncompressed option?

    I suppose you could still shoot enough video in uncompressed mode with a 8 or 16gb memory card.

    Or is there an entirely different reason why they don't offer uncompressed .mov for video?
     
  2. cube macrumors G4

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    #2
    miniDV uses JPEG compression and it takes about 12GB for 1 hour of video.
     
  3. MBX thread starter macrumors 65816

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    #3
    Yeah but i'm not asking for 1hr of video.

    I'd be happy if i could shoot 5-10min of uncompressed video instead of artifacted video of 15-25min in h.264.
     
  4. cube macrumors G4

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    #4
    Well *I* want MORE that 1 hour of CONTINUOUS video in 1 card.
     
  5. MBX thread starter macrumors 65816

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    #5
    But if you want that then get a real video camera?!

    The DSLR cam is obviously not meant to replace a real video camera but the quality this one offers is really nice therefore i'm a bit bummed they don't include a second option for uncompressed video even if you could shoot less of minutes.
     
  6. sammich macrumors 601

    sammich

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    #6
    So Canon is quoting about 18 minutes or something for 1080p/30 setting, but on which capacity card are they referring to?
     
  7. cube macrumors G4

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    #7
    It's not practical for one person to be switching between still and video camera.
     
  8. sammich macrumors 601

    sammich

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    #8
    I just realised this...JPEG compression? or uncompressed video? Uncompressed 1080p is anywhere from 1.5gigabits to 3 gigabits. So you'd be able to fit about 1 minutes seconds on your 16 gig CF card. But then you'd have to have a card that would write that fast.
     
  9. cube macrumors G4

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    #9
    This must be the stupid FAT32 4GB maximum file size limit.

    That is an oxymoron.
     
  10. robbieduncan Moderator emeritus

    robbieduncan

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    #10
    dpreview say video at 1080p is about 4.8 MBytes/sec. There is a hard-limit of 29minutes 59seconds per clip regardless of CF size. This is due to EU import taxes: 30 minutes or more per clip make is a video camera which attracts a higher tax rate...
     
  11. KeithPratt macrumors 6502a

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    #11

    Try 65 seconds of uncompressed video on an 8GB card...
     
  12. sammich macrumors 601

    sammich

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    #12
    Typed too fast :D fixed it for you.

    OKAY, here is your test...download a 1080p trailer from Apple Trailers, open it up in QT Pro, go to export, select the codec to be one of the uncompressed ones, then click export. Tell me what the bit rate on that baby is when it's finished.
     
  13. cube macrumors G4

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    #13
    There's no such hard limit. They should stop the stupidity and sell them at a higher price then.
     
  14. robbieduncan Moderator emeritus

    robbieduncan

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    #14
    Well, Rob Galbraith (and others) claim otherwise. I stand by my statement and have provided evidence for it: where's yours?
     
  15. sammich macrumors 601

    sammich

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    #15
    4.8mb/s is reasonable, it's in the blu-ray bitrate so it's good, but not great. This is a DSLR, not a production quality video camera.

    30 minutes is reasonable for most filming sessions. I mean it's not like you're going to film continuously for 30 minutes. Plus you might be changing lenses quite often so you'd be stopping anyway.

    Addendum: Check this showcase video for this camera. I took that 720p video and uncompressed it and got a lovely 500mbit rate. 10.5 gigs.
     
  16. cube macrumors G4

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    #16
    What claim? I said the EU tax is not a HARD limit. They should just not cripple the cameras and sell them at a higher price, paying the tax.

    Of course many people would be filming continuously more than 30 minutes to record events.
     
  17. Westside guy macrumors 601

    Westside guy

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    #17
    I think you've probably answered the initial question ("Why compression?") as well.
     
  18. alphaod macrumors Core

    alphaod

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    #18
    So maybe they should switch the file system to Ext3
     
  19. cube macrumors G4

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    #19
    No, i already said about the D90 that they should switch to UDF, which is multiplatform.
     
  20. alphaod macrumors Core

    alphaod

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    #20
    But isn't UDF for optical media?
     
  21. cube macrumors G4

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    #21
    You can format USB sticks and flash cards as UDF, no problem.
     
  22. Westside guy macrumors 601

    Westside guy

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    #22
    I think there are a few issues:

    • Inertia
    • FAT read/write support is very simple to implement
    • UDF support in certain OSes is incomplete. For example, OS X prior to 10.5 had limited support, and XP has limited support. Contrast this to FAT, which you can pretty much guarantee can be read anywhere with the stock OS.

    Wikipedia has a lot of info on this.
     
  23. Kebabselector macrumors 68030

    Kebabselector

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    #23
    For the market they are selling too (ie photojournalists) then the limit is fine. Though I can see why Canon should increase it, cos it'll keep you happy.
     
  24. Elektronkind macrumors member

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    #24
    Regarding filesystems, there are some reasons why ext3 and others aren't in use. The cells within flash memory have a finite lifetime in that their state (1 or 0) can be changed only so many times. This is what the write lifetime rating of all flash media refers to. File systems not designed for flash tend to update bits here and there with metadata, and often this metadata lives in a persistent area of the media so some cells are getting written to proportionally more than others.

    There are file systems designed with these limits of flash media in mind such as flashfs, but these haven't been widely adopted as support for them in mainstream OSes is scant, and I have yet to see a camera that knows anything other than FAT (FAT16 or FAT32.)

    So it's a chicken or egg problem. OSes don't support it because there are no devices out there that use it, and no devices use something like flashfs because none of the mainstream OSes support it.

    There are some other subtle technicalities... FAT is dead simple to implement as it's a really basic file system. REALY basic, so its requirements on the underlying hardware are very small... something that those little in-camera processors and accompanying DRAM can handle.


    /dale
     
  25. cube macrumors G4

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