AVCHD - Image Stabiliser and Cinema Mode...

Discussion in 'Digital Video' started by dkouts, Jun 16, 2009.

  1. dkouts macrumors member

    Joined:
    Apr 20, 2009
    #1
    Doing some R&D on editing AVCHD, reads like a minefield of problems.

    Anyone encountered these...

    http://support.apple.com/kb/HT3395

    and / or

    http://support.apple.com/kb/TS2646


    Dont you love Apples solutions to the problems?
    Dont use Image Stabilizer when you shoot and Dont use Cinema Mode.

    WTF - Why dont these f'n companies put some priority on standardizing a format and making it compatible across devices and stop coming out with a new video format every season. You want consumers to buy into a format, let the thing mature and become reliable.
     
  2. Courtaj macrumors 6502a

    Courtaj

    Joined:
    Jul 3, 2008
    Location:
    Edinburgh, U.K.
    #2
    That's the great thing about standards: there are so many of them around.

    That's the great thing about life: so many limitations to work around.

    All part of the challenge.
     
  3. dkouts thread starter macrumors member

    Joined:
    Apr 20, 2009
    #3
    Thanks courtaj - !

    so in spite of my ranting (!) anyone actually encountered either of these specific problems?

    would like to know if its definitely going to happen when I start to edit, coz I damn sure want to use the OIS and cinema mode.

    hopefully it was just a one-off bug that Apple posted the articles about, not a systemic problem that will happen every time OIS/cinema mode are used.

    ...actually Im just starting to wonder if the "jittery playback" they refer to is the progressive look, as opposed to super-smooth interlaced.
     
  4. sturigdson macrumors regular

    Joined:
    Apr 3, 2006
    #4
    I haven't encountered your worries exactly, but mostly because I have cut with AVCHD in Final Cut Pro, not iMovie. That said-

    1. CMOS- the problem with distortion is a known problem caused by the CMOS sensor's so-called "rolling shutter" design. Every camera that shoots a new CMOS sensor uses a rolling shutter, not a spinning shutter, and manages to get away with a good image if the camera is stable, movements are very slow and deliberate, etc. But watch out- when you move the camera, shoot hand held, shoot things that are moving very fast, particularly laterally, the new standard CMOS cameras just wreck the image. There's almost nothing that can be done with it.

    The problem described on the Apple page is this:
    Because of the CMOS rolling shutter problem, if you THEN apply the imovie image stabalizer to the image, it may, in "certain circumstances," actually further enhance the distortion of the video, making some very bizarre squishy images.

    For more on rolling shutters, and why they need to be immediately replaced in every camera, but won't be because they're cheap, see this:
    http://dvxuser.com/jason/CMOS-CCD/

    2. I think you're correct, the "flicker" described is actually due to the effect that these two camera brands (canon and panasonic) apply when the camera is in "Cinema Mode." Cinema mode usually describes a faux-frame parsing quality where the camera records false frames in order to achieve a movement more like the 24 frames of cinema. Cinema Mode attempts to be "like" a true 24p camera, which shoots a much more accurate 24 fps, but usually is a cheap knock off.
    If I were you, I'd shoot a bit of test footage in Cinema Mode and out of it, and see how it looks.
     
  5. LethalWolfe macrumors G3

    LethalWolfe

    Joined:
    Jan 11, 2002
    Location:
    Los Angeles
    #5
    AVCHD is a standard format, but as we continue to move more towards file based acquisition we'll see newer codecs coming out faster because we won't be locked to physical recording mechanisms like tape transports. Cameras are becoming more like computers every generation. Hell, the SI 2k camera (which was used for Slumdog Millionaire) is basically a computer w/a lens on the front of it. Camera manufacturers can be more flexible than editing software makers which is why editing software is always playing catch up. Also, codecs like AVCHD are very CPU intensive to playback and manipulate which makes them difficult to edit with. But as computers get faster we'll be able to edit the footage natively because the CPUs won't struggle as much w/the codec. Just like how DVDs used to require hardware assistance to play in a computer but these days anything will play a DVD.

    While I believe you are correct that the problem isn't w/using the OIS on the camera but using iMovie's stabilization feature your description of CMOS-based cameras just "wrecking" the footage is a large exaggeration. CMOS based cameras such as the Red One, Phantom HD, and Sony EX1 wouldn't be used for film and TV work if they produced "wrecked" footage. Not all CMOS cameras are equal though and it stands to reason that consumer cameras would exhibit the problem more often then professional cameras, but, even then, people have made some very nice looking images w/cameras like the HV30 and the video-DSLRs that have started cropping up.

    It's not just price that makes camera makers attracted to CMOS it's also the fact that they consume less power, generate less heat and take up much less space inside the camera. Also a spinning shutter, AFAIK, refers to the mechanical shutter on a film camera which acts similarly to the rolling shutter on a video camera. A global shutter, commonly used w/CCD cameras, would be when the whole imager gets exposed at once. If you have a fast enough spinning or rolling shutter then you can get close to effectively having a global shutter.


    Lethal
     

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