Video capturing

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    • #39728

      Here is a question I’ve wondered about but can’t find any definitive response on. When I’m capturing video to my computer from the DV camera, it gives me a couple of choices. I can capture to .AVI files, which are quite large, or RECORD DV AS MPEG, which it says compresses the file.

      So when I put the file as a movie file onto a DVD, am I losing a lot of quality if I capture the video in MPEG rather than AVI?

    • #171441

      MPEG is much more compressed than AVI, so an MPEG file takes up much less space. Movie DVDs use MPEG encoding to get a whole movie on one DVD. To accomplish this compression, MPEG uses a "lossy" compression scheme. By "lossy" I mean a small amount of the visual quality or detail is permanently lost when a video is encoded with MPEG. Now, just going through one MPEG-encoding doesn’t hurt too much, which is why movie DVDs look good. But every time video goes through another MPEG encoding, a little bit more quality is lost. So if you upload the video from your camcorder to your computer as MPEG, then edit it and encode the result as MPEG to put on a DVD, that’s 2 MPEG encodings your video has gone through! So most videomakers will upload as AVI, do all their editing and any intermediate saving as AVI, and only encode as MPEG when preparing to author a DVD. (I think Mac users sometimes use Quicktime files instead of AVIs, but I’ll leave those details to experienced MAC users.)

      Hope this answers your question, 🙂
      Ken Hull

    • #171442

      Just to try and expand on what Ken was saying, the way MPEG works, is it only records what has changed in a frame. So if the background is exactly the same and just the foreground image is moving, it only records where the foreground image moves to and what was previously unseen behind the foreground image in the background. Basically, if anything moves on screen (and by move, I really mean if pixels change color or shade), then that’s what MPEG records. This saves a lot of space in the file size, and can keep quality high.

      However, when you try to edit with this, you get wierd distortion when you splice two pieces of video together. During the transition, you’ll get really wierd distortion where it’s like some of the previous scene (the parts that haven’t changed yet in the new video and thus are ‘missing’ from the MPEG file) stay on screen for a few frames until there is movement in that area.

      In other words, MPEG is great for final output, but rather sucks for editing with. Now, there are ways to get around this by getting programs to pull that ‘missing’ information from the cut-out frames so the transition looks better, but if your going to do that, you might as well just go for uncompressed AVI because that is easier.

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