Is the AVI video format a uncompressed format?

Discussion in 'Amateur Video Production' started by Brian, Sep 14, 2010.

  1. Brian

    Brian Guest

    I have a video I'm working on using several video tracks. I want to
    save the video as a file then load it back into the video editor as a
    single video track then work on other things such as transitions etc.
    Is AVI the best file format to use? as I don't want to lose too much
    quality by saving to a file then loading the saved file back into the
    video editor gain. Is there one type of uncompressed AVI file or are
    their several types of AVI files?

    Regards Brian
     
    Brian, Sep 14, 2010
    #1
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  2. I suspect that you are working with "DV-AVI", a particular type. If
    so, it is frame-by-frame compressed at 5:1, and generally (with a
    good codec) you can recompress it with very little damage several
    times. I have removed my comparison of a 10-times recompression
    of DV-AVI using both the Raptor's codec and the MS codec, and
    while the results were different, the negative visible effects were minor.
    It is reasonable to "glue" edited material together so that you can bring
    it back onto the timeline as a single piece. This is NOT advisable with
    HD material, and that should all be exported only once from the
    timeline, preferably using a program that uses "smart rendering" (which
    doesn't recompress unchanged material) to avoid visible damage to
    the video (one reason I have not liked any of the Adobe video editing
    programs, at least through CS4 and Elements 7, is that they did not
    have "smart rendering" capability - and the codec used by Vegas for
    HD introduces no visible degradation with a single pass, unlike with
    some others). BTW, so long as you have backup copies of your
    source material on different drives, and also backup copies of your
    current edit, you should have little need for combining tracks before
    final output unless you are running out of vertical space for multiple
    tracks on your monitor, and/or you are doing something particularly
    complex.
    --DR
     
    David Ruether, Sep 14, 2010
    #2
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  3. Brian

    Brian Guest

    Thanks Jim and Dave for your replies and advice.
    I have DV tape camera which produces 720 x 576 frames in PAL. My video
    editor is Adobe Premiere Elements 8
    I am creating a special effects movie using a green screen background
    so I need to have the video clips on different tracks. This can be a
    problem in doing transitions as transitions seem to work better when
    there is a single video track. I have several scenes to edit and as
    soon as I get one of the scene the way I want it with the clips lined
    up on each track then it gets messed up when I'm working on another
    scene due to all the tracks on the timeline moving along when I remove
    a part of the video and close the gap.
    Maybe I'm expecting too much from the video editor I'm using
    (Adobe Premiere Elements 8) as freezing clips on the timeline is not
    possible in this program. In photoshop if you have a photo in several
    layers you can flatten it so it becomes one layer. It would be nice to
    be able to so this in a video editor with no loss to the video by
    combining several tracks into one track.

    REgards Brian
     
    Brian, Sep 14, 2010
    #3
  4. Brian

    Brian Guest

    Some time I might try multiple renders to find out how much quality I
    lose. I can see the benifits of a HD video comapred to a SD video as
    the HD video should be able to render more times than the SD can
    before the drop in quality is seen. HD video is usful if you want to
    zoom into the video when editing it as the quality is better after the
    zoom.
    There is some grouping in Premiere Elements 8 but this seems
    to apply for the thumbnail clips shown in the source window and not on
    the timeline. The program allow you to group the videos by lassoing
    them. What is ignoring is when you drop a video onto another video in
    the timeline then the video below will split apart. Holding dsown the
    Control key stops this from happening.

    Regards Brian
     
    Brian, Sep 15, 2010
    #4
  5. Brian

    HerHusband Guest

    Hi Brian,
    AVI and MKV are just "container" formats. They may contain a variety of
    different compression methods (for both video and audio). There's no way
    to know what compression is used just by looking at the file extension.

    If you have the disc space, AND your editor supports it, you might want
    to try the "Lagarith Lossless Codec", which allows you to save AVI files
    without any conversion losses. Another lossless codec is the "Huffy"
    codec, though I find Lagarith produces smaller files.

    I use the Lagarith encoded AVI's for my intermediate files when moving
    video between various applications, filters, etc. Then I select my final
    compression when I do my final editing.

    If your editor does not allow lossless AVI's, I have also had good luck
    using high bitrate MPEG2 files (9000kbps for SD video, 30000kbps or
    greater for HD video). While these are technically lossy formats, you
    would have to load and save many times to notice the losses visually.

    My personal workflow goes something like this...

    1. Copy the raw MTS (AVCHD compression) files from my camcorder to my
    hard drive.

    2. Use TMPGEnc Xpress 4 to combine the MTS clips and convert them to a
    single lossless (lagarith codec) AVI file.

    3. Process the video in VirtualDub as needed, using filters such as
    Deshaker and/or NeatVideo, saving the output back to a lossless AVI file.

    4. Use TMPGEnc Xpress 4 again to convert the lossless AVI into my final
    MPEG2 format (1080p30 @ 30000kbps).

    5. Do my final edits in Pinnacle Studio 14. The Studio editor only
    reencodes frames that have changes (transitions, titles, etc.), and
    copies other frames directly to the output.

    In theory, I could skip step 4 and load the AVI directly into my video
    editor, but converting to MPEG2 before editing makes the editing process
    faster and easier.

    Good luck,

    Anthony
     
    HerHusband, Sep 15, 2010
    #5
  6. This is correct, in my experience (remember my forced 10X rerenders
    experiment I used to have on my web site?). Two or three rerenders
    with DV-AVI (what you are using) should introduce minimal degradation.
    Worse, though, are the ill effects of using SD DV-AVI with green-screen,
    since that doesn't work very well (but try it to see what it looks like).
    Alternate a small change in color (or other minor change) with a return
    to the original for a clip to force rerendering. Without that, Elements
    will just copy the original and not rerender it (this is called "Smart
    Rendering", which Adobe does with DV-AVI, but not with HD,
    with which it rerendered everything, changed or not).
    This is NOT true, due to the MUCH higher compression of HD and the
    GOP rather than frame-by-frame compression of SD. HD should be
    compressed ONLY ONCE (as I pointed out before), at the time of final
    export. Most (all?) Adobe video editing programs do not do this properly
    with HD for minimum damage to the video... A plus for HD, though
    (beyond the obviously superior picture quality ;-), is the superior handling
    of green-screen material, since the pixels are much smaller in HD than in
    SD video.
    Yes, and some programs (Sony Vegas Pro 9 is one) will accept both
    video and stills of up to 4096x4096 pixels without reduction, permitting
    full 1920x1080 "roaming around" within the larger images.
    I don't remember Elements well enough to say, but in the Sony programs,
    including the cheap-but-VERY-good "Platinum 11", you can select items
    on the timeline and then hit the "G" key to group them, and they stay
    "glued" together until you select some and hit the "U" key (this will not
    work in Elements, but there may be a menu "switch" somewhere that
    locks together clips selected while holding down the "Shift" key...).
    --David Ruether
    www.donferrario.com/ruether
    [email protected]
     
    David Ruether, Sep 15, 2010
    #6
  7. Brian

    Brian Guest

    Thanks for the useful advice Anthony.
    My video editor can export to Microsoft AVI and Microsoft DV AVI as
    well as other formats such as MPEG. The manual claims that the
    Microsoft AVI is uncompressed and to use DV for better quality.

    Regards Brian
     
    Brian, Sep 16, 2010
    #7
  8. Brian

    Brian Guest

    Thanks David for the information.
    It's interesting to read the pro's ands con's with new technology such
    as HD video.
    I think I might avoid saving the video as a file and reloading until I
    experiment more on less vailable material. I was going to use DV-AVI
    but not if it's going to cause problems with a green screen special
    effect.

    I'm getting some earthquakes as I write where I live in Christchurch
    so I better send this message now while I can.

    Regards Brian
     
    Brian, Sep 16, 2010
    #8
  9. [...]
    Yes. While it took away some procedures and the ease of editing
    that were good with SD DV-AVI, it gave us a MUCH better picture,
    a good trade, I think... I'm astonished by how good the best HD
    is, and how cheap and easy it is to work with (with HDV tape
    and the excellent Canon camcorders that use this format). More
    attention may need to be paid to camera settings to get the best
    out of it (but limited alterations can be made while editing to fix
    minor shooting errors so long as the image was not shot overly
    saturated in any colors, or with blown-out highlights), but the result
    can be spectacularly good.
    Aaaarrrrggghhh! 8^(
    I hope all is OK now. I arrived in San Francisco just after the last
    "big" quake there. "Fun" driving the narrow mountain roads (very
    slowly...) while dodging the boulders all over the roads, not knowing
    if we would be blocked at some point attempting to get back to SF
    (we had driven down the coast to see Big Sur, but the mist made it
    invisible).
    --DR
     
    David Ruether, Sep 16, 2010
    #9
  10. Brian

    HerHusband Guest

    Thnx for the post. I have 3 HDV cameras, and two flash based HD
    If you don't need any intermediate processing (deshaking, noise reduction,
    or whatever), and your editor works smoothly with the raw MTS files, I see
    no reason to convert to a lossless AVI first. It would just add processing
    time and an unneccessary step.

    On the other hand, most editors are rather jumpy with AVCHD encoded MTS
    files, so converting to a less processor intensive format can make editing
    more pleasant. Especially if you have an older computer.

    I also like to convert the 20-40 individual clips from my camcorder to a
    single file for easier management.

    Anthony
     
    HerHusband, Sep 16, 2010
    #10
  11. Brian

    HerHusband Guest

    Brian,
    There "is" a completely uncompressed codec for AVI's, but the file sizes
    would be HUGE, especially for HD video.

    Codecs like Lagarith or Huffy are "lossless" but they do offer compression
    to keep the file sizes smaller and more manageable. They're like ZIP files
    you use to compress programs and documents, except they're designed for
    video. You do need to download and install these codecs separately. You
    should be able to find them with a quick Google search.

    As far as I know, the "DV" format is only available for SD video.
    Technically it is a lossy format, and if I'm remembering correctly, was
    similar to MPEG encoding. The big advantage to DV was that every frame was
    encoded individually, rather than relying on information from past frames.
    DV is a good format for editing if you are still working with SD video, but
    for HD you would probably need to find a different codec.

    Anthony
     
    HerHusband, Sep 16, 2010
    #11
  12. DV-AVI (SD) is a form of MPEG encoding, which compresses
    5:1 frame-by-frame - but additionally, it has a great error (dropout)
    correction mechanism for "borrowing" missing material for a given
    frame from the previous frame, so a small part borrowed may go
    unnoticed by most viewers. With tape HD (which does offer some
    advantages during editing and in image quality compared with
    memory-card media), a dropout causing a damaged frame will
    cause roughly a half second of picture freezing and audio silence
    due to the 13-frame GOP being interrupted. Fortunately, if the
    fault is near an end of a clip, or in still subject material, the offending
    frame can often be cut out without ill effects, and the GOP will
    reform. BTW, Adobe editors (Brian uses Elements) can be used
    for editing HD, but they have had serious limitations for doing so
    (I don't know if these have been corrected yet, or not...).
    --DR
     
    David Ruether, Sep 16, 2010
    #12
  13. Brian

    Brian Guest

    Hi David.
    At the moment we are getting many aftershocks from the 7.1 earthquake
    we got on 4th Sept in Christchurch. Most projects such as repairs to
    roofs are on hold until the aftershocks stop. The ground is unstable
    at the moment.

    Regards Brian
     
    Brian, Sep 17, 2010
    #13
  14. Umm, this must be a very "unsettling" experience...!
    --DR
     
    David Ruether, Sep 17, 2010
    #14
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