Watching a video backwards - Suse

This is a discussion on Watching a video backwards - Suse ; Is there a program that allows watching a video/film/movie backwards? From the end to the beginning? (I use opensuse 10.1; I have amarok, kaffeine and some others) Thanks, Filipe...

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Thread: Watching a video backwards

  1. Watching a video backwards

    Is there a program that allows watching a video/film/movie backwards?
    From the end to the beginning?
    (I use opensuse 10.1; I have amarok, kaffeine and some others)
    Thanks, Filipe

  2. Re: Watching a video backwards

    Prof. Filipe wrote:

    > Is there a program that allows watching a video/film/movie backwards?
    > From the end to the beginning?
    > (I use opensuse 10.1; I have amarok, kaffeine and some others)
    > Thanks, Filipe


    I imagine that would be tricky. AFAIK, most compress/encoded formats like
    mpeg4, mpeg2, etc. use intra-frames. For example, at time index 10sec the
    whole frame is stored in the file. However, for the next 10sec, only the
    difference (compounded?) are stored as the difference frames would be
    smaller.

    This is a hugely over simplified example and is flawed greatly, but it
    should give you the idea.

    So to play a movie backwards, the program would have to seek from the end of
    the file (not sure if this can be done either - perhaps mmap?) and find the
    last key frame. Then depending on how the intra-frames (like difference and
    stuff) are created, reconstruct the very last frame (frame n). Then repeat
    on frame n-1, then n-2, n-3, etc.

    If you find a program that does play a video backwards, please tell us/me. I
    would be very interested on how it was done!


    --
    Chris

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