At 21:42 17/6/00 -0700, l wrote:
>
>Can anyone offer any suggestions on video editing?
>
>Ideally I would be able to edit each frame of a quick time type movie that I
>would get off one of those cheapy I-Cams.
>
>But, it seems that the format, sort of like MPEG3 or something, doesn't work
>with frames, or snapshots.  It seems to use smaller bits of information.

Earlier versions of MPEG used to work by starting with a compeletely
specified keyframe (if I remember correctly), and then sending information
about the changes between frames, for a while. Then it would send another
keyframe and repeat the process. If there was not much action between
frames (especially if the camera stood still), then very little information
needed to be sent between keyframes, since each frame would have a lot in
common with the previous frame.

I don't know if MPEG3 works this way still, but I assume it does.

In order to edit the file, you need something that can read the video
format and extract individual images from it, allowing you to write back to
that format later. Video editing software often uses (used?) a format
called Motion JPEG, which stores all the frames independently, and just
uses JPEG compression on each frame. This does not allow as much
compression, but it makes editing quicker and simpler.

Video editing software that I have seen in the past on the Mac and Windows
often allows you to apply Photoshop filters to a video sequence (i.e.
frame-by-frame). I guess gimp plug-ins probably aren't allowed (yet?).


Ian


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