Annoying streaks when creating a video from .jpgs

Discussion in 'Amateur Video Production' started by Cecil Cooper, Feb 16, 2004.

  1. Cecil Cooper

    Cecil Cooper Guest

    I am a newbie -- but only because I've been having this problem for so
    long. I've been trying to create videos from digital images I have
    stored on my hard drive. When the video has been rendered, the
    fade-in from black and the fade-out to black produces uneven streaks,
    especially in areas of the image that are very light. For example, a
    blue sky will not fade out smoothly, but has these incredibly
    irritating bands across the sky, that obviously don't look natural and
    in my opinion defeat the purpose of this whole thing.

    Originally I was using Adobe Premiere and I thought maybe that the
    issue was with the CODEC that I had chosen. But I just tried an
    evaluation copy of Memories on TV, which is simple software that seems
    to do exactly what I want. Same problem! I tried burning it onto a
    DVD, the fades look pretty much the same.

    Is this a problem with the source photos? I am using jpegs of fairly
    large resolution approx 1700x1100 pixels. I also tried using some
    scanned in .tif files of approx the same resolution.

    This is absolutely maddening. Can anyone suggest a solution? I just
    want to figure this out and what I'm trying to do is so simple yet...
    this looks pretty awful.

    Thanks,
    Cecil
     
    Cecil Cooper, Feb 16, 2004
    #1
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  2. Cecil Cooper

    Samuel Paik Guest

    Are you looking at the result on a television or on your computer?
    You may be looking at a perfectly good interlaced transition on
    a progressive display (i.e. on your computer).

    Sam
     
    Samuel Paik, Feb 16, 2004
    #2
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  3. Cecil Cooper

    Cecil Cooper Guest

    Are you looking at the result on a television or on your computer?
    I'm looking at the results on my computer screen. I will give it a
    shot on the TV (what i really care about after all) and see what it
    looks like.

    Bearing in mind that I know NOTHING about this stuff -- why would a
    regular DVD movie look fine on both a computer AND a TV, while this
    one might only be suited to the regular TV screen?

    Thanks for the advice, I'll post again if this is successful.

    Cecil
     
    Cecil Cooper, Feb 16, 2004
    #3
  4. Cecil Cooper

    Jukka Aho Guest

    These two web sites might help:

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

    <http://www.cs.tut.fi/~leopold/Ld/FilmToVideo/#Speeds>

    The software-based DVD video player on your computer knows the
    difference between progressive frames (film) sourced material
    and interlaced material, and processes the images accordingly.

    Displaying progressive frames sourced material on a computer
    monitor (which usually runs in a progressively scanned video
    mode) is trivial, whereas displaying interlaced video frames
    on the same monitor (using the same, progressively scanned
    video mode) is not.

    In the end, it is your target format (i.e. the final format
    where the video will end up after you have finished with
    editing it) that determines to correct way of dealing with
    the streaking problem.

    If your target format is DVD or video tape, no special
    measures need to be taken: interlacing is just a cosmetic
    problem that will only show up on the computer screen
    while editing but not in your final end product, which
    is viewed on a tv screen. Then again, if your target
    format is computer screen or paper (say, you are going
    to embed the video on a web page or print out still
    images) you usually need to deinterlace.
     
    Jukka Aho, Feb 16, 2004
    #4
  5. Cecil Cooper

    PTRAVEL Guest

    I don't know the other program, but I routinely do photomontages in
    Premiere. I never use jpgs -- only TIFFs, and I resize them to the maximum
    size that Premiere will accept, i.e. 4,000 pixels for the longest dimension.
    For movement around the still, use the Image Pan Transform, not the Motion
    Filter (this is for 6.5 -- the transform has been dropped from Pro).

    Everything I've done renders smooth as glass.
     
    PTRAVEL, Feb 17, 2004
    #5
  6. Cecil Cooper

    Samuel Paik Guest

    A very quick discussion, really basic information on video and film,
    which any good introduction to video will explain in greater detail
    with illustrations.

    Moving pictures consists of a series of "frames", pictures, which are
    displayed one after the other at a particular rate. Most film movies
    are displayed at 24 frames per second (fps). NTSC video (US) is
    a smidgeon less than 30 fps, and PAL/SECAM video is 25 fps.

    In order to save resources (money and bandwidth), video is displayed
    using "interlaced" scan. Each video frame is split into two "fields",
    a field consists of half of the lines in the frame, the odd field
    consists of the odd lines, and the even fields consist of the even
    lines. Interlaced scan displays one of the fields, then half a frame
    time later displays the other field. While displaying the video,
    the fields are offset by half a field line height (or one frame line
    height) so each field covers an area on the display that fits
    within each other like a comb.

    So, the odd lines and the even lines are displayed at different times.
    To get a really smooth dissolve, you have to compute the even lines
    to occur at a different time of the dissolve as the odd lines, hence,
    when you look at a frame, the odd lines will be a different intensity
    as the even lines.

    Now, about film--a film frame, of course, is shot all at a single instant.
    So a frame of video that represents a frame of film will look unified.
    There actually is some complexity with converting film to video which
    I'm not going to discuss, but if you look at each frame of video from
    a film, you'll be "surprised" (if you look at the each actual video
    frame, rather than the output of your DVD player, which is preprocessing
    the DVD video to look good on your computer screen).

    Sam
     
    Samuel Paik, Feb 17, 2004
    #6
  7. Cecil Cooper

    stankley Guest

    For anyone confused about interlacing/telecine/progressive/3:2
    pulldown, I suggest this excellent article that I came across - it
    taught me a lot.

    http://www.dvdfile.com/news/special_report/production_a_z/3_2_pulldown.htm

    Paul.
     
    stankley, Feb 18, 2004
    #7
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