Client Check List
Ready to get your project underway? Here's some questions
we'll ask you when you contact us.
Don't know the answer to some of these questions? No problem
-- get in touch with us and we'll walk you through it; that's
what we're here for.
How long is the title?
The length of the title, along with the number of audio or
sub-picture streams to be included, has a direct impact on
the potential video quality. This is because the video, audio,
and sub-picture information all take up space on the disc.
The total amount of information on the disc determines at
what "bit rate" the video can be encoded. Generally speaking,
the higher the bit-rate, the higher the quality. An average
bit-rate of at least 3.5 megabits per second is frequently
mentioned as the minimum that can yield acceptable quality
for most content. Therefore, it is highly advisable to calculate
the total amount of all audio, subpicture, menus, DVD-ROM
content, and any other material to be included on the disc
such as logos and trailers prior to encoding the video.
Subtracting the amount of space used for these elements from
the total disc space available will determine how much space
is available for the main video feature. Once this calculation
is made, the bit-rate for the video can be calculated to utilize
all remaining disc space. Determining this bit-rate will indicate
if the project can be done as a single-sided, single layer
(DVD-5) disc or if the additional space of a single-sided,
dual-layer (DVD-9) or a double-sided, single layer (DVD-10)
disc is required.
For more information regarding audio, sub-picture, menu,
logos, trailers, and DVD-ROM content please see the sub-headings
regarding these subjects listed below.
The determination of how to allocate this average bit rate
is part of the expertise that Motif provides in the encoding
process. The first step in the encoding process is to run
the video to be encoded through the encoder so that a determination
can be made of what scenes might require more and what scenes
might require less bits to encode.
In DVD, it is possible to MPEG encode the picture applying
more "bits" to complicated scenes and less "bits" to less
complicated scenes. As part of the encoding process, we always
hold some bits in "reserve" in case some very complicated
scenes can benefit from "extra bits".
This type of compression is referred to as "variable bit
rate compression" (or VBR) because unlike "constant bit rate
compression" (or CBR), which always uses a fixed number of
bits without regard to image complexity, VBR can help to optimize
encoding quality by applying more bits to where they may be
needed.
MPEG works by looking at a picture and noticing redundant
information in the scene and between the scenes, and what
factors are always changing in the scenes. MPEG reduces the
amount of data it needs to store in this redundant information.
For instance, if the scene is of a man talking against a
static background (the classic talking head), there is probably
a lot of redundancy in the scene -- walls, clothing, etc.
On the other hand, if the scene is a panning shot of a field
of tall grass blowing in the wind, there might be so much
in this image that is unique and changing within the frame
and from frame to frame that there is little redundancy.
By using variable bit rate compression, less bits can be
applied to the static scene and more to this very complex
scene.
One of the issues that will cause the issue of bit rate and
length to be re-examined is the implementation of dual layer,
dual sided discs (DVD-10 and DVD-18). As these disc configurations
and their manufacturing become more commonplace, the ability
to have relatively high bit rates and voluminous amounts of
content on a disc will make the DVD format even more impressive.
^
What format is the source master?
A digital component source master on D1 or digital Betacam
is preferred because the compression process itself is component.
In component recordings, the color information is recorded
separately from the black and white information. This process
creates a master where the colors are sharper and the artifacts
commonly associated with composite recordings such as "chroma
crawl" are absent.
Some of these composite artifacts create additional non-redundant
information, which wastes the precious bits used in the encoding
process. An analogue component recording such as from BetacamSP
is actually preferable to a digital composite master such
as D2 for this very reason. This is not to say that it is
not possible to encode from a composite source, but a digital
component master is always preferable.
If a composite or analog source is provided, we will create
a digital component master from which we will encode.
^
Will the disc contain additional material
such as logos, trailers, interviews, etc.?
In determining the overall bit rate, all video material,
including disclaimers, FBI warnings, logos, and trailers must
be taken into account. It's also important to make certain
that all material that needs to be encoded is available at
the same time so that encoding can take place efficiently.
^
How many audio tracks and in what configuration?
Obviously, the number and type of additional tracks will
have a bearing on the overall average bit rates for the disc.
In addition, the preparation of language tracks for AC-3 encoding
is an important element in the making of a DVD disc.
The format supports Dolby Digital that can exist in a stereo
configuration that can be compatible with ProLogic Surround
or 5.1 channel surround sound. This 5.1 channel sound is so
named because there are front left, front center, front right,
rear left, rear right and a subwoofer channel (the .1 channel
in the name).
If these tracks already exist for theatrical release, it
is possible that they can be used for DVD. However, these
tracks may require additional audio post production to optimize
them for the DVD format.
If 5.1 channel tracks do not exist and are desired, then
they will need to be prepared. In addition to the lead time
necessary to prepare sound tracks, it is important to be able
to locate additional foreign language elements and to verify
that they exist in the correct format and to the same master
to which video is being encoded.
One of the challenges in efficient DVD title creation is
to ensure that all the elements necessary for authoring --
all video, audio, and graphic elements are available and approved
so that authoring can take proceed.
An interesting specification built into the DVD format is
that Linear PCM audio (such as used on Compact Audio Discs)
can also be used. The DVD format also supports 96Khz Uncompressed
PCM audio that has twice the bandwidth of today's current
audio CDs. The fidelity of this sound format is phenomenal
although files are quite large and will consume additional
"real estate" on the disc if used.
^
Will the disc contain subtitles, closed
captioning, or other sub-picture information?
Another important element of the DVD format is sub-picture
information. It is important to gather this information and
to ensure that it is in a format compatible with the DVD authoring
process, and to create and approve any sub-pictures that will
be created specifically for the disc. Closed captions, subtitles
and other previously created text data will need to be converted
to a computer file that can be read by the authoring system.
The DVD format supports up to 32 channels of subpicture information.
These sub-pictures are essentially graphic files that are
"bit-mapped" or overlayed onto the pictures one pixel at a
time. The color palette for sub pictures consist of 16 different
colors and contrast values, 4 colors and 4 different contrast
values can be displayed on the screen in one channel at a
time.
By using the various channels of sub-picture information
that can be triggered by time code or button depressions,
relatively sophisticated graphics, even simple animation can
be put onto the screen. Sub-pictures can scroll and fade on
the screen and can change every field. More basic uses of
sub-pictures are captions, sub-titles or other text information.
^
Will the disc be released in a 4x3 or 16x9
format?
The DVD format allows for the specification of an aspect
ratio in the display of the disc. The disc itself can be programmed
to allow for a 16x9 format transfer to be displayed that way
on 16x9 televisions as well to also force the display of a
scope or 1:85:1 film in a "letterbox" on a 4x3 television
set.
^
Will the disc be PAL or NTSC?
DVD discs can be PAL and NTSC. To create a NTSC disc, the
video is encoded from a 30 frame 525 line digital component
or NTSC source master. To create a PAL disc, the video is
encoded from a 25 frame 625 line digital component or PAL
source master.
The format also can have different audio configurations in
its NTSC and PAL versions. In an NTSC Player, AC-3 Audio and
Linear PCM audio playback capability is mandatory and MPEG2
audio playback capability is optional. Originally the DVD
specification made MPEG2 audio and Linear PCM audio playback
capability mandatory and playback AC-3 Audio capability optional
in PAL players, but the specification has been revised so
that the MPEG2 audio requirement for PAL players and discs
is no longer mandatory.
Nevertheless, this means that in order to have NTSC and PAL
product, the disc needs to be mastered, encoded and authored
in both formats.
^
What will the on-screen menus look like?
The DVD format allows you to 'program' what the disc does
when it is put in the player, what options you allow the user
to select and how to access the content. The design of the
menus and the on screen controls requires both good graphics
and interface design. The features of the player and the remote
control can be enabled via the menu screens.
The goal is to provide a straightforward interface to the
player and to still create a compelling polished graphics
look. Motif can help create menus and screen graphics that
differentiate your brand and product. The use of still images,
animation, and graphics enhance the "look and feel" of the
disc.
^
Will the disc contain chapter stops that
allow a "jump" to a particular part of the content?
Like laser discs, the DVD format can provide for "Chapter
Stops" that branch a user to a particular scene. Unlike laser
discs, a DVD menu screen can be programmed with images of
the particular screen, with on-screen buttons or "hot spots"
that when selected, cause the disc to begin playing the selected
scene. These menus can be quite attractive, especially when
thumbnail images are used for these buttons or "hot spots".
^
Will the disc contain DVD-ROM content and/or
Internet access capability?
It is possible to include content and Internet access capability
on DVDs specifically tailored for use on computers with DVD-ROM
drives. This content is added to the disc during the authoring
process in a directory or group of directories that is readable
only by a DVD-ROM drive on a computer containing appropriate
software applications. If you wish to include such content,
Motif can provide information and guidance.
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