video capture dimensions too small

Discussion in 'Professional Video Production' started by John Rowell, May 16, 2005.

  1. John Rowell

    John Rowell Guest

    This is a follow-up to my message from May 13 regarding the DVD
    resolution problem. As it turns out, the video being captured onto the
    computer is captured at 360x240. At that size it appears crystal clear.
    But in converting to DVD specs, it has to be resized to 720x480 which
    results in that blurriness I notice. So my question is, why is the video
    being captured at only 360x240 resolution? Is this camcorder incapable
    of transferring video at the proper resolution, or is this some software
    or driver setting? This holds true for DVIO, Ulead Video Capture 7.0,
    and Windows Movie Maker. In fact, in Windows Movie Maker it shows
    320x240 as the capture size. I'm using a Sony TRV19 minidv camcorder and
    a firewire connection capturing as avi.

    John
     
    John Rowell, May 16, 2005
    #1
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  2. John Rowell

    PTravel Guest

    I'm unfamiliar with the software that you are using. The TRV19 exports its
    video through the 1394/firewire port as standard DV025 720 x 480 video.
    Make sure your capture software is set to save the captured video as
    DV-codec encoded AVI. Most likely, it will use the Microsoft DV codec. If,
    for some reason, that isn't installed on your computer, an internet search
    should turn up a downloadable Panasonic DV codec, which will work just as
    well.
     
    PTravel, May 16, 2005
    #2
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  3. John Rowell

    Jukka Aho Guest

    In my reply to your original message, I suggested capturing a test clip
    with DVIO and opening it in VirtualDub (version 1.6.0 or later.)

    If you do this and then choose "File" -> "File information..." from
    VirtualDub menus, what do you see in the "Frame size" and "Decompressor"
    fields?
     
    Jukka Aho, May 16, 2005
    #3
  4. John Rowell

    John Rowell Guest

    Frame size: 720x480, 29.97 fps
    Decompressor: Internal DV decoder

    So I guess this means it is actually being captured at 720x480 after
    all. What I'm noticing appears whenever there is any movement. Perfectly
    still shots appear ok.

    I posted two frame captures for your review. First one, camera is
    panning slowly. Second one, camera is still.
    http://www.discountpv.com/images/capture1.png
    http://www.discountpv.com/images/capture2.png

    John
     
    John Rowell, May 16, 2005
    #4
  5. John Rowell

    C.J.Patten Guest

    Looks like a DV artifact to me - perhaps the result of over-active edge
    sharpening?

    I tried to find the manual for your camcorder online but wasn't able to. (it
    may be there - it wasn't an extensive search ;)

    In any case, you should look in yours and try to disable edge-sharpening.

    One way to accomplish this on my Sony camcorder is to shoot with "Soft
    Portrait Mode". By default, a lot of the consumer Sonys have edge sharpening
    on by default in an attempt to make the picture look clearer. In my
    experience, it just leads to "jaggies." Put another way, you don't get
    something for nothing.

    Try that and do a test. It *might* help.

    C.


     
    C.J.Patten, May 16, 2005
    #5
  6. John Rowell

    Mike Fields Guest

    That looks remarkably like what I see when I have the field order set
    wrong (I am one of those people who can get it wrong 98% of
    the time on something that has a 50/50 chance ... )

    As far as the size being wrong, somewhere in the back of my
    mind I remember some problem with the MS DV codec that
    set it to 1/2 size or something. Seemed to me there was some
    sort of patch or something that would set it to the right size -
    seems WMP was also involved somehow. I managed to miss
    that one, so I don't remember the exact details but google should
    turn up some hits on it.

    mikey
     
    Mike Fields, May 17, 2005
    #6
  7. John Rowell

    Jukka Aho Guest

    Taking in account that you were capturing with DVIO (which is probably
    the simplest DV capture program in existence and doesn't have any
    adjustments for the incoming data), it would have been a very odd
    problem indeed if it wasn't that way. :)
    It's beginning to sound a lot like an interlacing problem now. (Or,
    rather, a problem with coming in terms with how interlacing works in
    digital video. But that can be cured! :)
    Yep, the problem (or what you see as a problem) is almost definitely
    caused by interlacing. Do you see these kind of effects as well:

    <http://deinterlace.sourceforge.net/screenshots/TitanicBefore.jpg>

    If you do, and if you think that's a defect, you will probably want to
    read this:

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

    and this:

    <http://www.100fps.com/>

    In short, interlacing is the way how normal video (and tv) works - by
    displaying alternating odd and even fields instead of frames. It's not a
    defect, but a fundamental feature of the system. The only reason why it
    looks so bad on a computer screen is because many computer programs will
    display both fields at once, combined into a single frame, which is an
    unnatural way of viewing interlaced video. A normal tv set will never do
    it that way, but display the fields in a smooth sequence instead.

    Whether you want to get rid of interlacing or not depends on your final
    target format. If your final target format is DVD, there's absolutely
    _no need_ to remove interlacing. On the contrary, deinterlacing would
    only make the image quality worse: you would lose half of the original
    vertical resolution and half of the temporal resolution - the image
    would appear more blurred and the motion would become jerky.

    That being said, sometimes you may have a problem with making all the
    tools to understand the proper field order of your interlaced video
    clips. For example, if the MPEG-2 encoder - which you will invariably
    use at some point in your toolchain for encoding the video into a DVD
    compatible format - is not properly set up, it might instruct the DVD
    player to play back the fields in a wrong order. If the field order is
    encoded in a wrong way, it will manifest itself as a very jumpy and
    distracting motion quality - especially when playing back the disc on a
    stand-alone DVD player and a regular tv set.

    Another thing to look out for is resizing the video. Interlaced video
    should _never_ be carelessly resized in the vertical direction, since
    that will mess up the interlaced field structure. The only exception to
    this rule is if you're using an NLE application that is _aware_ of
    interlacing and will calculate all scaling (and other effects) on a
    field-by-field basis, instead of frame-by-frame basis.

    (If the application you're using is not like that, there are other, more
    advanced tricks you may use, such as converting the interlaced video
    into a ~60 fps progressive video stream [for processing], and then back
    to interlaced again. Employing this trick doesn't take away from the
    motion quality and can be accomplished quite easily with e.g. AviSynth -
    allowing you to use filters and tools that were never meant for
    processing interlaced video in the first place - but that's probably not
    anything you should be worrying about at this stage.)

    * * *

    In conclusion, interlacing is neither a defect nor a problem (although
    it may _look_ that way on a computer screen while editing) and - despite
    it often being suggested in these situations - deinterlacing is usually
    _not_ the answer.

    If you're having problems with your interlaced video and your final
    target format (which, as I gathered from your original post, is DVD) I
    believe it's either because you're (possibly) scaling the video in the
    vertical direction at some point during the editing and processing (in
    some application that does not know how to handle interlaced data
    properly), or the field order is not set up correctly in your MPEG-2
    encoder.

    Also note that in order to assess the quality of the DVD's you produce,
    you should be viewing the final result on a stand-alone DVD player and a
    regular, interlaced tv set. The computer monitor and computer-based
    software DVD players do not show you the whole truth.

    * * *

    You mentioned something about Windows Movie maker. If that's what you're
    using to edit the video before burning to a DVD, make sure you have the
    latest version (2.1), and that you're using the DV-AVI format all the
    way (not WMV!). See this site for more details:

    <http://www.windowsmoviemakers.net/>
     
    Jukka Aho, May 17, 2005
    #7
  8. John Rowell

    John Rowell Guest

    Thanks for your explanation of this phenomenon. You described exactly
    what I'm experiencing and why. And those links were very helpful.

    John
     
    John Rowell, May 17, 2005
    #8
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