In a video of mostly empty frames is there an easy way to extract any that have stuff

Discussion in 'Digital Video' started by Spanky Deluxe, May 27, 2008.

  1. Spanky Deluxe macrumors 601

    Spanky Deluxe

    Joined:
    Mar 17, 2005
    Location:
    London, UK
    #1
    I've just been filming the dark sky to see if I can capture any lightning. There's been some lightning but my videos are quite long and its a pain trying to find the frames with lightning bolts in. Is there a simple way to do this? I.e. to search through a file and look for changed frames?
     
  2. Lunja macrumors 6502

    Lunja

    Joined:
    May 15, 2005
    Location:
    Lincoln UK
    #2
    In short, not that I'm aware of. You'll just have to manually scrub through your footage, mark the in and out points and capture them in the normal way.

    It's likely that, unless you are using a high-end camera, that what you think are blank frames actually do have some info in them. The camera will be trying to compensate for the lack of light by increasing the gain, and this will make a picture look noisy (similar to the picture of a TV that hasn't been properly tuned), so even if a piece of software existed that could analyse footage, it's unlikely that it would see 'blank' frames anyway...

    PS. Fell free to post up some of your edited clips :)
     
  3. AviationFan macrumors 6502a

    AviationFan

    Joined:
    Jan 12, 2006
    Location:
    Cedar Rapids, IA
    #3
    With off-the-shelf tools, I wouldn't know how to do this. What you could do is export the video as a still image sequence, using an easy-to-read format such as BMP, and then write a small program that looks at the brightness of pixels in those BMPs and filters out the ones that have brightness above a certain threshold. If you have a little programming experience, that shouldn't be difficult to do.

    - Martin
     
  4. jettoblack macrumors member

    Joined:
    Nov 1, 2006
    #4
    How about the sound? Assuming the video was mostly quiet otherwise, if you scrub the timeline with audio waveforms enabled, you should see a big spike whenever there is thunder?
     
  5. wedgie macrumors newbie

    wedgie

    Joined:
    Feb 11, 2007
    #5
    "and then write a small program...": Suggesting someone to go write a program to solve their problem is not much of a helpful response. You might as well have said something like "close your eyes and make a wish." :p
     
  6. AviationFan macrumors 6502a

    AviationFan

    Joined:
    Jan 12, 2006
    Location:
    Cedar Rapids, IA
    #6
    wedgie,

    What I described is breaking the original problem apart into two smaller ones, one of which can be solved with existing tools, while the other one requires some simple programming work. Not knowing if the OP has any programming experience, I realize that this may not directly lead to a workable solution of the problem for the OP, but it could. Or it might prompt a response from another forum member along the lines of "Hey, I know a simple solution to the second part of the problem!".

    I was just trying to help...

    - Martin
     

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