Videotape
VHS videotape is still a viable distribution option preferred for audiences that are resistant to change.
CD
There are several ways to distribute video on CD’s. They
have been especially popular as a medium for motion pictures using the
MPEG 1 standard. The quality of these “video
CD’s” is about the same as VHS.
Some DVD authoring software can be used to make CD’s that behave
like DVD’s. The total run time for these disks is about
fifteen minutes. The special software needed to play back the CD
content is included on the disk. These CD’s are for
computer CD/DVD drives only and are generally programmed to run the
software automatically when the disk is inserted. While this is a
viable way of distributing DVD-quality video to computer users, its
usefulness diminishes as new computers are delivered with DVD drives as
standard equipment.
It is also possible to make CD data disks that contain MPEG 2 or
Windows Media Format files. Most computers now have the codecs
needed to play MPEG 2 or WMF files. Again, at about four Mb/Sec a
CD can hold about fifteen minutes of video. The increased
compression of the WMF format allows more than sixty minutes on one
CD. The WMF format fits the specifications for MPEG 4, the
compression regimen designed to accommodate high definition
television. Both Quicktime and Real Player also offer compressed
video formats that can be included on data CD’s. The
appropriate players will have to be downloaded by your viewers.
Finally, there is software available for authoring data CD’s, or
CD-ROM’s. These software packages allow the integration of
files on the disk with files on the internet in addition to many of the
navigation features common to DVD’s.
DVD
One popular way to distribute video is the DVD. A DVD is an optical
disk, actually a reflective film sandwiched between two protective
acrylic layers, like a CD, but with some differences. The most
important difference is that a typical DVD can hold up to 4.7 GB of
data, including formatting information on a single layer disk and twice
that on a dual layer disk. You have roughly four gigabytes of
space available for project on a single layer disk.
There are two ways of using DVD technology to distribute video.
The traditional method is to use DVD authoring software to create a DVD
that can be played on a stand-alone DVD player, typically called a
“set top” player. Set top players require a
specific MPEG 2 format which makes it nearly impossible to
reverse-engineer the video for editing. This DVD format is ideal
for distribution. In small quantities you can make your own
DVD’s with relatively inexpensive software and hardware.
Color printers capable of printing directly on the DVD face are very
affordable as well. It should be noted that from the beginning
there have been problems with compatibility between DVD-R and DVD+R
disks and some set top DVD players, especially models made before 2001.
For large quantities you’ll want to use a commercial disk
replicator. Replication is a two step process. First a
glass master disk is made. Then the master disk is used to press or
stamp a reflective disk, which is then sandwiched between two acrylic
layers for protection. The minimum cost for replication is
usually the same as the cost of making 800 to 1000 copies. In
other words, whether you ask for one hundred, two hundred, or a
thousand copies of your masterpiece, the total cost of replication (not
including album cases or other packaging) will be about the same.
Most commercial disk replicators will now accept a DVD-R as a master,
although the preferred medium for mastering DVD’s is DLT, or
digital linear tape. DLT was developed to backup or archive
computer networks and servers. If you want digital copy
protection for your DVD’s you will have to submit your masters on
DLT.
When dealing with a commercial replicator, be prepared to be able
to prove you have the right to use all of the audio and video on your
disk. Replicators do not like to be sued.
Making a DVD
A DVD can be as straightforward as a videotape. Pop it in the
player and the program runs from start to finish with no
embellishments. Or it can have a complex system of menus allowing
the viewer to select various programs or go to specific points within
programs. Menus can allow viewers to select different audio
channels or call up subtitles.
The first step in making a DVD is to assemble all of your finished
media as digital files. There are only limited opportunities to
edit materials in DVD authoring software. It is best if all of
your materials are in final form before you go any further. Audio
files should be in the .wav format. Your video files are probably
either Quicktime or .avi files. They must be converted to MPEG
2. This option should be available in your video editing
software. If you have optional audio tracks you can convert your
video using your primary mix of audio tracks, then save your secondary
mix of audio tracks separately as a .wav file. You can do this by
turning the appropriate tracks on or off before exporting the
file. In addition, you may have still images you want to use in
your DVD, perhaps as menu backgrounds or buttons. Full frame
stills should be 640x480 pixels for NTSC or 640x576 for PAL. Your
DVD authoring program will change these stills, which have square
pixels, to 720x480 or 720x576 pixels where the width of each pixel is
nine tenths of the height. The difference is pixel aspect between
digital stills and digital video affects all of your still images,
whether full frame or smaller.
Your authoring software will allow you to import video, audio, and
still image files. The categories may be straightforward or have
more imaginative names, such as “Media,”
“Backgrounds,” and “Buttons.”
At this point it may or may not tell you if your project will fit on a
DVD. You have about four gigabytes available. If your
project is too large you can go back to your video editing software and
change the MPEG 2 conversion settings to increase the compression and
decrease the file size of each MPEG 2 file. While the DV files
you generally work with in your editing software are compressed to
about four Megabytes per second, MPEG 2 files are generally compressed
to from 3.5 to 8 Megabits per second. At the lowest compression
you have a little over an hour of video on a DVD. At the highest
compression you can get about two hours on a disk. As you
increase the compression of your video files you also increase the
chance that you will lose detail in your video during quick
movements. The loss of detail will take the form of
pixilation. Your video will be reduced to a jumble of blocks
until the rate of video change returns to a more normal rate. You
should probably keep your data rate at four megabits per second or
higher.
There is actually more to the MPEG 2 format than the data rate.
While in the DV format compression is achieved frame by frame, MPEG 2
is divided into groups of pictures (GOP’s) usually twelve to
fifteen frames long. The first frame (I) of each GOP has all of
the information necessary to reconstruct the frame. The remaining
eleven to fourteen frames (P and B frames) contain only enough
information to reconstruct the video by combining information from
previous frames (P frames) or by combining information from both
previous and following frames (B frames).
The best consumer authoring programs will allow you to import your
video and use it to create all of your menus and buttons in a very
straightforward and intuitive way. Typically, once you’ve
imported your video clips you can select one of several menu
styles. If you have more than one video clip, you can assign each
clip to a button on the menu. You may even be able to create
intermediate menus and use the time line of your video you can select
chapter points and drag those points to menu buttons. In some
cases the video from the clip will form a still image in the button
automatically. When you’re done you usually have at least
two options: burn one or more DVD’s using the current project
settings, or create a file that is an exact image of the contents of
the DVD. When you burn your DVD’s from the current project
your program will create a temporary file on your hard drive in which
all of your materials are converted into the required DVD format.
Your disks are burned from the temporary file, which is deleted as soon
as the disks are done. When you elect to create an image file,
the file is created on your hard drive but no disks are burned.
You can use the image file to burn your disks later as you need them.
Professional software will allow you to do anything you’ll see on
a commercial DVD. Professional software is not, as a rule, either
user-friendly or intuitive. It is more powerful and flexible.
The Internet
Using video on the internet creates a set of considerations and
problems that should be part of the video planning process before any
video is shot. The basic fact about the internet is that it was
never designed to transmit video and audio at four megabytes per second
or even four megabits per second. To send video over the internet
more compression is necessary.
There are several compression schemes for internet video that rely on four ways of reducing picture information.
1. They generally reduce the frame size.
2. They reduce the frame rate.
3. They reduce the amount of information in each frame beyond the
compression available in MPEG 2 by sacrificing picture quality when
content in moving and maintaining higher resolution when images are
relatively still.
4. They “buffer” the bit stream.
Reducing the frame size reduces the amount of picture detail available
and should be an important consideration in shooting for the internet.
640x480 pixels
320x240 pixels
160x120 pixels
Loss of detail can turn excellent images into mud. Just as
commercial motion pictures are often shot not for the resolution
available with 35mm film, but with the more limited resolution of NTSC
video in mind, you should shoot for resolutions much lower than
standard video.
After decades of experimentation the film industry settled on a few
frame rates. For silent consumer film either sixteen or eighteen
frames per second was used. There was a noticeable flicker when
films were projected at these rates. Commercial sound motion
pictures are projected at twenty-four frames per second. The
frame rate for NTSC television is thirty frames per second. Frame
rates for streaming video are often below fifteen frames per
second. The impact on motion is obvious. At fifteen frames
per second, how many frames does it take to swing a baseball bat?
The third method of reducing the data rate, sacrificing detail during
motion sequences, further “muddies” the picture.
Motion and fine detail are mutually exclusive in the world of streaming
video.
Buffering can be as simple as actually downloading the entire video at
one rate in order to play it back on a computer at the designed normal
rate. More commonly, playback is delayed until enough data has
been downloaded to allow playback of a significant part of the
video. When the playback catches up with the download (and runs
out of data to play) the playback is paused until more data is
downloaded. This process often causes awkward pauses during
playback, but that’s progress.
Streaming video should accommodate a range of users, from those with 56
Kbps dial-up modems to those with DSL and cable modems receiving in
excess of one gigabit per second at the modem (but less than 54 Mbps
over their wireless network). When you export video from your
editing software you will have the option of two or three streaming
formats. Pick the one you believe will offer your viewer the best
picture quality, given the content of your video) with the least
inconvenience and delay. Each of these will in turn allow you to
choose either a single streaming rate or multiple rates dependent on
the viewer’s reception rate.
All that’s left to be done is to move the finished streaming video file onto a web site for downloading.
Archiving your work
Most of the time most artists want their work to last at least as long
as they live. Throughout recorded history we have been able to
save some pieces of art or literature on cloth, paper,
stone, or metal. Each of these has properties that cause
the information to degrade, but all have one thing in common: It
does not take any equipment beyond the human eye to recognize and read
the information, although the eye may need a brain behind it trained in
hieroglyphics or ancient Greek.
Times have changed. Your hardware may become obsolete or even
incompatible with newer operating systems. Changes in the
computer world have given an entirely new meaning to the word
“legacy.” Until recently the word referred to
property inherited or traditions passed down from one generation to the
next. In the computer world “legacy” has become an
adjective referring to the data in any application that can no longer
be used by readily available software or hardware. The 5 ¼
inch floppy disk is a legacy system in that no computers sold today can
read those disks. The 3 ½ inch floppy disk is pretty close
to legacy status itself. As you move from one operating system to
the next or from one capture card to a different brand you risk
rendering all of your .avi files unreadable. Keep the tape.
And while you are at it, take very good care of your playback
equipment, too.
So far we’ve gone through the following videotape formats:
Two-inch quad, one inch helical of various formats up through type C,
half- inch EIAJ reel to reel, U-Matic and U-Matic SP, Betamax, VHS,
Betacam and Betacam SP, M2, S-VHS, 8 Millimeter, and Hi-8 analog
formats; DV, Digital 8, DV Cam, DV Pro, Digital Betacam, a more.
If your tape is stored properly at moderate temperature and humidity
you are more likely to have trouble finding playback equipment than you
are to have trouble with the videotape itself.
The best you can do is to make copies of your work in the highest
quality digital format you believe has a user base large enough to keep
it in use for a long period of time and that you can afford.
While many are choosing to “archive” their work on DVD in
MPEG 2, that medium is much more highly compressed than the DV format,
which is in general use and slowing replacing both VHS and 8mm as the
recording format of choice, both by amateurs and many
professionals. For works under fifteen minutes DV files can be
stored as .avi or .mov files on DVD-R disks without further
compression. A dual layer writable disk could hold up to thirty
minutes. With the advent of high definition video there is no way to
know how long the equipment to play back standard definition tapes will
be generally available, while current DVD drives and both blue laser
disk formats can play material on existing DVD-R disks. Properly
stored DVD-R disks should last at least one hundred years, while
rewritable disks can be expected to last at least twenty-five
years. Considering the formats and equipment in common use
twenty-five years ago, you should be prepared to re-record your work to
new formats as it becomes advisable or necessary.
