frequently asked questions

Discussion in 'DVD Video' started by juke_joint, Apr 27, 2005.

  1. juke_joint

    juke_joint Guest

    What is the purpose of alt.video.dvd?
    Discussion of DVD hardware and software for computers
    and home entertainment systems; also information and
    entertainment (movies) released on DVD.

    Can I advertise in alt.video.dvd?
    All advertising, whether "on-topic" or not, is subject
    to being reported to the sender's ISP and/or web host.

    Advertising is:
    - Any offer to sell or trade.
    - Any message designed to drive traffic to the
    sender's web site.
    - Any message designed to generate email responses.

    A 4-line or less "sig" attached to a legitimate
    question or comment is not considered advertising.

    What is DVD?
    DVD stands for Digital Versatile Disk. It is a
    multi-purpose technology suited to both entertainment
    and computer uses.

    A DVD is identical in thickness (1.2 millimeters) and
    diameter (120 millimeters or 4.7 inches) to a standard
    Compact Disc, but that's where the similarities end.
    The DVDs storage capacity is seven times that of a
    CD, with a 4.7-gigabyte capacity on a
    single-side/single-layer DVD. That's the data-storage
    equivalent of a 133-minute movie, thus allowing 95
    percent of all movies to fit comfortably on a
    single-layer DVD, eliminating the need for "flipping"
    the disc and leaving extra room for multiple audio,
    language, and subtitle tracks; bonus materials; menu
    screens; and other features unique to DVD. This
    capacity is nearly doubled (8.5 GB) on a
    single-side/dual-layer DVD, and quadrupled (17 GB) on
    a double-side/dual-layer DVD, allowing DVD to flourish
    not only as a movie-lover's format, but as an
    amazingly flexible medium (DVD-ROM) for
    high-definition computer games and multimedia
    applications. In short, this makes DVD the home
    entertainment and multimedia format of the new
    millennium.

    What are the features of DVD-Video?
    The main features of the various DVD formats are:
    - Backwards compatibility with current CD media.
    - All DVD hardware will play audio CDs and CD-ROMs
    - Physical dimensions identical to compact disc but
    using two 0.6 mm thick substrates, bonded together.
    - Single-layer/dual-layer and single/double sided
    options.
    - Up to 4.7 GB read-only capacity per layer, 8.5 GB
    per side maximum.
    - Designed from the outset for video, audio and
    multimedia, not just audio.
    - All formats use a common file system (UDF).
    - Digital and analog copy protection for DVD-Video
    and DVD-Audio built into standard.
    - Recordable and re-writable versions.

    Not only do movies look great on DVD, but they also
    include lots of interesting additional material and
    interactive options. The DVD format was designed from
    the beginning to support interactive features
    including menus and indexing, alternate audio and
    video tracks, and even user-controlled branching
    within the material.

    Most movies also include additional material such as
    movie trailers and behind-the-scene documentaries, and
    sometimes additional scenes that were cut from the
    movie. DVDs can provide support for the hard of
    hearing and for alternate languages.

    The alternate audio track also is often used for a
    director's commentary, in which the entire movie is
    accompanied by voice-over discussion by the creative
    team, describing their thinking while it was being
    created and edited.

    Some DVDs also provide multiple camera angles for the
    video, so you can switch points of view as it plays.

    Why is the quality of DVD-Video so much better
    than VHS?
    DVD video is a higher resolution than VHS. Standard
    VHS video has 320 dots per line and DVD video has
    720 dots per line. However, DVD video quality still
    depends on many production factors (including the amount
    of compression used) and the display device it is viewed on.

    DVDs will usually (but not always, see dvd rot) last much
    longer than videotape.

    Will DVD replace VCRs?
    Eventually. DVD has many advantages over VCRs,
    including fundamentally lower technology cost for
    hardware and disc production.

    What is MPEG?
    DVD video is compressed from studio CCIR-601 format to
    MPEG-2 format. This is a "lossy" compression which
    attempts to remove redundant information (such as
    sections of the picture that don't change) and
    information that's not readily perceptible by the
    human eye. The resulting video, especially when it is
    complex or changing quickly, may sometimes contain
    "artifacts" such as blockiness or fuzziness. It
    depends entirely on the quality of compression and
    how heavily the video is compressed. At average rates
    of 3.5 Mb/s (megabits/second), artifacts may be
    occasionally noticeable. Higher data rates result in
    higher quality, with almost no perceptible difference
    from the original master at rates above
    6 Mb/s. As MPEG compression technology improves,
    better quality will be achieved at lower rates.

    MPEG-4 is the current state-of-the-art for video
    compression technology. The two older technologies
    MPEG-1 and MPEG-2 already caused a widespread
    distribution of digital video on the PC and notebook.
    The successor of MPEG-4 is already on the horizon and
    is called MPEG-7. This video standard principally
    integrates an object search routine. MPEG-2 will also
    be extended; MPEG-21 is the succeeding standard.

    What are "regional codes," "country codes," or "zone
    locks"?
    Motion picture studios demanded that the DVD standard
    include codes which can be used to prevent playback of
    certain discs in certain geographical regions. Players
    sold in each region will have that region's code built
    into the player. The player will refuse to play discs
    which are not allowed in the region. This means that
    discs bought in one country may not play on players
    bought in another country.

    Regional codes are entirely optional. Discs without
    codes will play on any player in any country. It's not
    an encryption system, it's just one byte of
    information on the disc that the player checks. Some
    studios have already announced that only their new
    releases will have regional codes. Presumably, once a
    DVD movie has achieved worldwide release it could be
    re-released without encoding.

    There are 6 regions:
    - North America
    - Europe
    - Japan
    - Australia & Far East (except Japan)
    - Africa & Middle East
    - Central & South America

    I tried to copy a DVD. Why didn't it work?
    Copying DVDs is prohibited by the DMCA (Digital
    Millennium Copyright Act) and usually prevented with a
    Macrovision (or equivalent) circuit in every DVD
    player. Composite video output will have a rapidly
    modulated colorburst signal along with pulses in the
    vertical blanking signal to confuse the
    automatic-recording-level circuitry of VCRs.
    Unfortunately, this can degrade the picture,
    especially with old or nonstandard equipment.

    Macrovision is designed to guard against casual
    copying (which the studios claim causes billions of
    dollars in lost revenue), but it doesn't stop pirates.

    What is the DMCA?
    The DMCA is the Digital Millennium Copyright Act,
    passed by the U.S. Congress in 1998, supposedly to
    update copyright law for electronic commerce and
    electronic content providers. Unfortunately, this law
    is very poorly written, and is now regularly used by
    corporations to restrain the three primary concessions
    of copyright and otherwise prevent free speech
    activity:

    1. Fair use is the right to make unauthorized copies
    of works for certain protected purposes - mainly for
    academics, reporting, or criticism. When a student
    quotes a book in a high school paper, she is making a
    fair use, and can't be stopped by the copyright owner.

    2. First sale is the right to sell purchased media
    over and over again, as long as you don't make any
    copies. When you read a book, then sell it to a used
    book store to be bought and read by someone else,
    you're exercising your rights under first sale.

    3. Limited time - copyrights are granted for a limited
    time. After that time expires, the work goes into the
    public domain - it can be copied and used by anyone,
    for any reason.

    The DMCA has one particularly bad section, called the
    anti-circumvention provision. That section makes it a
    crime to break encryption used to prevent someone from
    getting access to electronic content, or to "traffic"
    in a tool used to do so.

    A friend told me that if you cover the inner ring of a
    DVD with a black marker, you will disable the
    Macrovision. Is this true?
    No, you can't disable Macrovision that way.

    There is an audio-CD copy protection that can be
    disabled that way - the disc contains phony data to
    throw off CD-ROM players so they can't read the CD.
    Audio-CD players will in theory not try to read that
    data and ignore it but some are affected anyway. The
    fake data is indeed located on the inner ring and can
    be made unreadable by using a marker.

    Is there a noticeable difference in the Superbit
    version of a movie...?
    The whole "point" of Superbit is to have superior
    sound and video quality for the movie. If you compare
    a superbit version with a non-superbit version,
    chances are, superbit is better quality, even if there
    are no extras... but now the studio seems to be
    getting into "Superbit Deluxe" where one disc is a
    high-quality video/audio transfer of the film, and the
    second disc is a bunch of extras.

    It takes good equipment to appreciate the difference.
    Like a really good player (Pioneer Elite, Philips,
    Marantz, Onkyo, etc.), good cabling, and an HDTV.

    HDTV's, particularly 16x9 HDTV's, can not only show
    the full resolution that a DVD sends, but can also
    engage an anamorphic mode which delivers 2-3 times the
    resolution normally allowed. With this kind of
    resolution available, the improved quality of Superbit
    can be seen.

    What happens if I scratch the disc?
    DVD includes a better error-correction system than CD.
    Most scratches will cause minor raw data errors that
    are easily corrected. Major scratches may cause
    anything from unrecoverable errors that will show up
    as a momentary glitch in the picture to a complete
    failure.

    Is CD-ROM compatible with DVD-ROM?
    Yes. All DVD-ROM drives will read CD-ROMs (Yellow
    Book). However, DVD-ROMs are not readable by CD-ROM
    drives.

    Will DVD support Digital TV (HDTV)?
    HDTV is not supported by DVD, but the designers have
    it in mind. Since HDTV uses MPEG-2 it will be easy to
    "upgrade" the DVD format. The limited data rate of DVD
    may make it difficult to support high-quality HDTV,
    but this can be solved by either increasing the spin
    rate (as with multi-speed CD-ROM drives) or
    using higher-capacity blue lasers.

    Some have speculated that a "double-headed" player
    reading both sides of the disc at the same time could
    double the data rate. This is impossible since the
    track spirals go in opposite directions. The DVD specs
    would have to be changed to allow reverse spirals on
    the second side.

    What are the outputs of a DVD player?
    Most DVD players will have the following output
    connections:
    Video:
    - RCA composite video (NTSC or PAL)
    - S-video (NTSC or PAL)
    Audio:
    - Dual RCA stereo analog audio (with Pro LLogic)
    - Digital audio (coaxial FM and/or IEC-9588 optical).
    Requires an external decoder or an amplifier/receiver
    with built-in Dolby Digital or MPEG-2 audio or
    PCM stereo) support.

    Some players may have additional connections:
    - Component (YCrCb; NTSC or PAL)
    - RF video output for connecting to TV witthout direct
    input. (Panasonic DVD-A300)
    - 6 RCA jacks for surround sound output frrom built-in
    decoder. (Panasonic DVD-A300, RCA.)

    What are the sizes and capacities of DVD?
    There are many variations on the DVD theme. There are
    two physical sizes: 12 cm (4.7 inches) and 8 cm (3.1
    inches), both 1.2 mm thick. This is the same form
    factor as CD. A disc can be single-sided or
    double-sided. Each side can have one or two layers of
    data. The amount of video a disc can hold depends on
    how much audio accompanies it and how heavily the
    video and audio are compressed. The oft-quoted figure
    of 133 minutes is apocryphal: a standard DVD can
    actually hold up to 6 hours of video and audio if it's
    heavily compressed (which reduces the quality).

    What are aspect ratios?
    Video can be stored on a DVD in 4:3 format (standard
    TV shape) or 16:9 (widescreen). The 16:9 format is
    "anamorphic," meaning the picture is squeezed
    horizontally to fit a 4:3 rectangle then unsqueezed
    during playback. DVD players output widescreen video
    in three different ways:

    - letterbox (for 4:3 screens)
    - pan & scan (for 4:3 screens)
    - anamorphic or unchanged (for wide screens)

    Note: Some 16:9 discs are playable in widescreen and
    letterbox modes only, if the producer chooses.

    For letterbox mode the player uses a "letterbox
    filter" that creates black bars at the top and the
    bottom of the picture (60 lines each for NTSC, 72 for
    PAL). This leaves 3/4 of the height remaining,
    creating a shorter but wider rectangle. In order to
    fit this shorter rectangle, the picture is squeezed
    vertically by combining every 4 lines into 3. This
    compensates for the original horizontal squeezing,
    resulting in the movie being shown in its full width.

    For pan & scan mode the video is unsqueezed to 16:9
    and a portion of the image is shown at full height on
    a 4:3 screen by following "center of interest"
    coordinates that are encoded in the video stream
    according to the preferences of the people who
    transferred the film to video.

    For anamorphic mode the video is stretched back out by
    widescreen equipment to its original width.

    In widescreen or letterbox mode if a movie is wider
    than 16:9 (and most are), additional thin black bars
    will be added to the top and bottom at production time
    or the sides may be cropped (possibly with a small
    amount of additional panning).

    Video stored in 4:3 format is not changed by the
    player. It will appear normally on a 4:3 screen.
    Widescreen systems will either stretch it horizontally
    or add black bars to the sides.

    Some producers may put 16:9 source on one side of the
    disc and 4:3 source on the other, since "full-frame"
    4:3 movies have additional picture at the top and
    bottom rather than panning and scanning. (The
    cinematographer has two sets of frame marks in his
    viewfinder, one for 4:3 and one for 1.85, so he can
    allow for both formats).

    The 16:9 anamorphic format causes no problems with
    line doublers, since they simply double the lines on
    their way to the widescreen display which then
    stretches out the lines.

    What is progressive scan?
    One of the primary tasks of the MPEG decoder inside
    every DVD player is to take the 24 fps data stored on
    the DVD and convert it to 60-fields-per-second video
    for TV viewing. Since 24 doesn't divide evenly into
    60, a process called "3-2 pulldown" is employed, where
    3 video fields are created from the first film frame,
    then 2 fields from the next frame, then 3, then 2,
    3-2-3-2-3-2, etc. The result is 60-fields-per-second
    interlaced-scan video, and that's the end of the story
    for non-progressive-scan DVD players.

    Progressive-scan DVD players add an important
    additional step to create a better-looking picture
    they generate a progressive-scan video signal through
    a process called de-interlacing (sometimes called
    "line-doubling"). The de-interlacer's first task is to
    look at the interlaced video signal as it leaves the
    MPEG decoder and determine whether its original source
    was 24-frame-per-second film or 30-frame-per-second
    video. The original frame rate determines the type of
    processing necessary to create an optimized
    progressive-scan signal.

    At least that's what progressive-scan DVD players
    are supposed to do. However, most of the inexpensive
    models just double up the lines and create even more
    motion artifacts.

    What is "DVD rot?"
    DVD rot makes discs unplayable by impairing the
    ability of their aluminum layer to reflect light. Its
    most likely causes include oxidation caused by air
    coming into contact with the reflective layer, a
    galvanic reaction between a dual-layer disc's gold and
    aluminum coatings, and a chemical reaction triggered
    by impurities in either the disc's adhesive or in the
    aluminum itself.

    The vast majority of reported cases of DVD rot have
    been shown to be due to poor quality control during
    the manufacturing process or user mishandling. DVDs
    are a delicate audio/video/data storage device that is
    held together by a laminated outer surface containing
    layers of plastic and reflective metal coatings, and
    held together by special glues.

    If manufactured with proper quality control at the
    production line end, placed and removed properly from
    its storage case when used, and stored properly by the
    consumer, DVDs will definitely outlive their video
    tape counterparts.

    How can I convert some of my old home movies on VHS
    and 8mm to DVD?
    The "Guides" section of http://www.doom9.org/ has all
    the information you need on this and many other DVD
    topics.

    Where can I learn how to burn my own DVDs?
    http://www.videohelp.com/

    I just got a DVD player and it pauses, skips and
    pixilates a lot when I'm trying to watch a movie. What
    causes that?
    If you are having these problems on more than one disc
    it's probably the DVD player. Inexpensive or
    "throw-away" players are much less reliable than
    higher-priced (>$100) models.

    Where can I find the best prices for movies on DVD?
    http://dvdpricesearch.com

    Which is the best video connection to use; RF,
    composite, S-video or component?
    Assuming you use decent quality cables, component
    video is the best.
    Ranked by quality from worst to best;
    - RF
    - Composite
    - S-video
    - Component

    Where can I download movies off the net?
    A reputable on-line retailer. You "upload" your CC
    info, and then you can "download" all the movies you
    want. Downloading commercial movies without paying is
    illegal.
    juke_joint, Apr 27, 2005
    #1
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