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  1. Member
    Join Date
    Feb 2007
    Location
    United States
    Search Comp PM
    Hi there-

    I'm a little new to the encoding process and I have a couple of questions if someone could help me out. I am trying to assemble a software demonstration comprised of screen captures (captured with SnapzX Pro), a narration audio track, and PowerPoint Presentation slides.

    The basic issue is that I cannot produce a decent video quality when I export my completed movie. The video quality produced by the component pieces - SnapzX Pro and the PowerPoint Quicktime movie - is very good and I'd like to know why I can't seem to match that quality, one for one, when I export the video after editing it, even if I leave the settings as raw video with no compression.

    I've tried several methods to compile this video, including:
    Final Cut Pro:
    - export PowerPoint slides as images
    - import images into Final Cut Pro
    - add transitions, audio track, do basic editing
    - export, testing many different encoders and settings
    iMovie:
    - export PowerPoint presentation as quicktime movie
    - import movie into iMovieHD
    - add audio track
    - export, testing many different encoders and settings

    I would really appreciate any suggestions as to how I can match the import video quality with the final export quality.

    Thanks so much, folks-
    Jordan
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  2. Line art and computer graphics are surprisingly difficult to bring into video.

    Standard video resolution is only NTSC 720x480 or PAL 720x576.

    So you get the best possble quality by doing the lines and graphics with NTSC 720x480 or PAL 720x576 from scratch. If you want to see the correct proportions, you can set the app to use pixel aspect ratio for NTSC 4320:4739 = ~0.912 and for PAL 128:117 = ~1.094 if you are doing 4:3 projects, for 16:9 projects and more related info see:

    http://www.sjoki.uta.fi/~shmhav/SVCD_on_a_Macintosh.html#aspect_ratios

    Sure, you can compose at NTSC 640x480 or 656x480 etc or PAL 768x576 or 788x576 etc, but then the ultimate scaling to NTSC 720x480 and PAL 720x576 will produce horizontal scaling artifacts.

    Now, with that approach we have a crystal clear video! Every input pixel corresponds just one pixel in the output video.

    ...but it is now TOO sharp so thin lines flicker badly on a TV! So we have to slightly blur the video so it looks decent on a TV. Camcorders do this blurring automatically.

    http://www.adamwilt.com/Tidbits.html#CGs

    http://www.lurkertech.com/lg/fields/fields.html

    ...so try to capture the computer display at some video-like resolution so the scaling to video doesn't distort it. Or capture at high resolution and intelligently downsample it to video resolutions while adding a slight blur to it.

    Does SnapzX Pro support have any info about the recommended settings if you plan to output to video and TV?
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  3. Member
    Join Date
    Feb 2007
    Location
    United States
    Search Comp PM
    First of all, thanks so much for the help and online resources!

    I'm a bit confused about the pixel issue, however. My final output is a streaming web video, so the video that I'm producing will always be viewed on a computer monitor. How then, are those square pixels converted to rectangles?

    For example, with the Quicktime movie exported from PowerPoint: does the Quicktime encoder convert those square screen pixels to rectangles when I export the file from PowerPoint, or does the editor (iMovie or Final Cut Pro) convert the pixels when I import the source PowerPoint movie? Or perhaps are they only converted when I output the final product from the editor as an .mpeg or .mov?

    I'm not sure if you can tell more about the problem by actually seeing the difference in video, but I've posted a couple of images so that you can see what I'm talking about, if that helps.

    Here is a screenshot of the Quicktime Movie exported from PowerPoint:
    http://www.designfad.com/video/goodscreen.jpg

    Here is a screenshot of a quick test I ran, outputing the final, edited video from iMovie as uncompressed video (five seconds is abou 320 megs):
    http://www.designfad.com/video/badscreen.jpg

    Thanks again for the help!
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  4. > so the video that I'm producing will always be viewed on a computer monitor.

    OK. Then you can forget what I said about rectangular pixels and the need to blur the video.

    You can work with simple square pixels and you can keep the video sharp because you are not going to present it on a TV. You mentioned FCP and iMovie so I presumed you worked with DV video where those problems apply. Sorry for the confusion.

    Thanks for the screenshots! It seems like the DV codec introduces compression artifacts to the the bad image. I just tested this and converting a 720x576 clear TIF screenshot to 720x576 DV via QT Player, and the DV codec introduced similar artifacts to the output image.

    So you should definetely avoid using the DV codec for this kind of work.

    > does the editor (iMovie or Final Cut Pro) convert the pixels when I import the source PowerPoint movie? Or perhaps are they only converted when I output the final product from the editor as an .mpeg or .mov?

    The DV codec usually uses rectangular pixels. Usually any other codec (MPEG1 and MPEG2, for example) that uses resolutions like 720x576, 720x480, 704x576, 704x480, 360x288, 360x240, 352x288, 352x240 and similar are rectangular pixels, too.

    If you insist using iMovie, you could experiment using iMovie's HDV 720p or 1080i projects. Also in HDV there are compression artifacts but the better resolution will better hide them.

    The sampling matrix of HDV 1080i is 1440x1080, and its pixel aspect ratio is 4:3 = ~1.33, so for square pixel display it must scaled to 1920x1080.

    The sampling matrix of HDV 720p is 1280x720, and its pixel aspect ratio is 1:1 so it uses square pixels.

    Those HDV resolutions may big somewhat too large for computer playback, though.

    Or just forget iMovie/FCP and use QT Player Pro or other tools and better codecs (H.264 or animation? Anyone?) for this task to edit the video.
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