It should be said before you go any farther
that working with multimedia, especially desktop video, can be a frustrating
experience. Not everyone will have problems, but our experience has been that
the equipment and software used in multimedia production is often "on the
cutting edge" and is not as robust as products in the more established areas
(such as word processors). Asking your computer to handle the massive amounts of
data involved with video may make it somewhat "cranky," and you shouldn't be
surprised by occasional crashes.
Macintoshes are usually more stable than
Windows machines for desktop video, but neither is perfect. We've personally
been up all night working to meet deadlines because our capture card didn't
function properly, our editing package had bugs in it, and our modeling program
crashed repeatedly.
This is not to say that you will have problems,
but rather to let you know that if you do, you're not alone, and may not be
doing anything wrong. Just remember to leave some room in your deadlines for
unexpected problems, especially with new hardware or software. Keep your system
extensions and devices to a minimum. Once you've got your system working really
well, back it up (especially the System folder) so you don't have to start from
scratch if the multimedia gremlins attack.
And no matter what happens, just keep in mind
that it is poor multimedia etiquette to throw an uncooperative computer out of
the office (bystanders tend to complain ;-)
Now, if all this hasn't scared you off, let's
get started.
Making multimedia movies involves several
different steps which are briefly outlined below:
1. Start with your source material. Higher
quality originals will give you better final movies.
2. Capture the video
3. Edit your video with an editing program. You
can also add special effects to your video at this stage. Save the edited file
uncompressed (the file will be fairly large).
4. Compress your movie. The compression step is
often overlooked, yet has a dramatic impact on your final movie quality. You
must compress your movies prior to distribution.
5. Distribute your final compressed movie. If
you're making a CD-ROM, you'll probably use an interactive authoring tool and
then "burn" a CD-R of the final project. If you're putting video on your site,
you have to add HTML code to control movie.
Compression for
WWW
Trying to take a huge
file and push it through the low-bandwidth WWW is even harder than trying to
make it play properly on a CD-ROM. Data rates are often 1/10th to 1/100th the
size of a CD-ROM. Needless to say, this makes compression absolutely critical -
anything you can do to improve how well your movie compresses will help.
Web data
rates
As you all know, the
Web has lower bandwidth than a CD-ROM. Users are often connected with extremely
slow connections and you must make your movies as small as possible so that
people can view them. Data rates range from about 50 Kilobytes per second (KBps)
for fast connections down to only 2.5 KBps for 28.8 modems. Movies usually don't
look so great at modem speeds.
Several different file
formats exist for working with digital video files on a computer. These formats
can be conveniently divided into three categories:
Once you have
installed a video capture board, turn your attention to the software that you'll
use to actually perform the video capture. Video capture software can be divided
into two groups:
Generally, dedicated
video editing software has more functionality than hardware-specific software
provided with your board.
Several commonly used
video capture software packages are:
Adobe Premiere
Asymetrix Digital
Video Producer
Ulead Systems Media
Studio Pro
Corel
Lumiere
After the video stream
has been digitized, the main objective is to set the desired frame rate, frame
size, and data rate. These factors have direct impact on the success of your
delivery. Improper selection of any these video attributes causes quality and
bandwidth problems. If the video requires editing such as removing unwanted
frames or adding transitions, most video editing packages allow you to do this
at the same time that you set the size and the frame and data
rates.
Setting these
attributes is directly linked to the compression scheme you select. Certain
codecs are more effective when, for example, certain frame sizes are selected.
VDOWave is optimally designed to work best with 160 x 112 frame sizes, while
MPEG-4 allows a much wider selection of frame sizes. Each attribute has its own
characteristics that you need to understand in order to select the most
effective codec for your content. The next section, "Compression and Storage,"
should be read carefully to answer many of your questions concerning this
production phase.
If you want a general
overview of the video capture through editing and conversion process, read the
"Sample Content Creation Scenario" section later in this
article.
What is the MPEG format?
MPEG stands for the Moving Pictures Expert
Group. The group create standards for digital video and audio
compression as part of the International Standards Organisation. The
format allows compression rates of 50:1 to 200:1. It is not currently the
most popular video standard on the WWW, but due to future developments it could
well be in the near future. There are currently four types of MPEG digital
audio and video in use or planned for the near future;
MPEG-1 : This format was designed for CD-I and Video-CD media, it is a standard which allows a transmission rate of 1.5 Mbps.
MPEG-2 : This format is the standard for digital TV and D.V.D.s (Digital Video Disc). This is an advanced version of layer-1, with the ability of coding interlaced images above 4 Mbps.
MPEG-3 : This is an audio compression standard.
MPEG-4 : This standard is planned for late 1998. A problem with many past standards was video and audio synthesis. This standard is supposed to overcome this standard as well as other improvements like an artificial intelligent approach to reconstructing images.
How is the video data
compressed?
There are basically five techniques to compressing data.
Advantages of
MPEG
Disadvantages of
MPEG
MPEG compared to other
formats
The future
I can see MPEG becoming the future most popular format,
not only of computer video files, but also of home entertainment as DVDs become
the next VHS, and as Digital TV takes off. The formats will probably come
together, as is already beginning to happen, as Quicktime is going to be used as
the basis of MPEG-4. All the companies like Sun, Microsoft,
IBM and Apple will
start to work together with MPEG to develop future formats.
What is the AVI format?
AVI format was developed by Microsoft as part of Video for
Windows. AVI stands for Audio Video Interleaved. The drivers and
player come with Microsoft Windows '95 and NT, if you have not got them because
you use OS/2 or an Apple Mac you can get the drivers easily. It is a
special case of the RIFF (Resource Interchange File Format). RIFF is a
clone of the IFF format invented by Electronic
Arts in 1984. It was vented for Deluxe Paint for the Amiga, and when
Deluxe Paint went to the PC, so did IFF.
With software
alone AVIs will play full motion video and audio in a small window at about 15
frames per second. AVI use a number of different codecs. There were
originally two codecs, Video 1 and RLE (run length encoding), other codecs have
been developed by third parties such as Indeo and Cinepak. These codecs offer Mac
compatibility and audio compression.
Advantages of AVI
Disadvantages of
AVI
AVI compared to other formats
The Future of AVI
Without the money of Microsoft the format will probably
die in the near future. The organisations involved like Indeo will try but
there is not much point trying to compete with MPEG-4, already these companies
are developing towards MPEG-4, making drivers and players etc. It is going
to be a very popular universal format, and AVI can't be improved to a level
anywhere near it when MPEG has got so many people involved in it's development.
What is the Quicktime format?
Quicktime is a format developed by Apple Mackintosh and
is the most popular video format currently available on the internet. New
developments in MPEG-4 are utilising quicktime, so existing content may be able
to still be played on an MPEG-4 player, which will certainly please Apple as they would be able to encourage
companies to create their web video in Quicktime format so it can be easily
converted in the future to MPEG-4, which means more money for them now.
The Quicktime Pro 3 Package is available
currently at Apple for US$29.99. The new Quicktime 3 player can be downloaded
for free too.
Advantages of Quicktime
Disadvantages of
Quicktime
Quicktime compared to other formats
The future of Quicktime
Presently it looks like Quicktime and MPEG will
eventually merge. Apple will have a large roll to play in MPEG-4 and
further developments in the future by the group. It is probably better for
digital video if it is developed by non-commercial organisations. Then the
technology will be open for other groups to utilise and improve upon. The
technology will move quicker, and due to the competition prices should be kept
low.
There is a large amount of video available on the internet for download mainly in the formats covered by this site. There is also live streaming video. Don't expect long movies, the best you can get without a very long download is a short clip, a couple of minutes at the most. Streaming video is usually low resolution, small screened and has a low frame rate. Another problem is that the video may stop while the audio continues. These characteristics are due to the speed of the data transmission over the internet. The type of connection you have will affect the quality of the video. The question is though, are we going to see better quality video streams in the future? Or is every advancement in video compression technology going to be counteracted by increasing levels of internet traffic caused by more users?
Compressing Video
Content
As discussed earlier
in other sections, video files can get quite large depending on their frame
rate, frame size, and color depth. For example, a 320 x 240, 15-fps video clip
captured at 24-bit color can require a data rate of 3.46 MB per second to see
and hear it. The key to playing video files over a network of limited bandwidth
or storing video files on a computer hard disk is compression with codecs. Many
codecs are available for differing video needs. For example, some codecs are
optimized for low bit rates, while others are optimized for high bit rates.
Others have optimal frame sizes and frame rates. As part of the planning
process, it's important to determine what these factors are for your content,
and with this understanding you'll be better able to select a codec optimal for
your video needs. This list of codecs is not comprehensive, but provides a
summary of video codecs commonly used when creating multimedia
content.
Streaming
video
Streaming video
sounds like a good feature of the Internet, it's video on demand but you will
need at least a 120 MHz Pentium processor and a 28.8K modem, and software, that
could take a while to download. VDO, Vivo, Real
Networks and Net Toob offer free
downloadable software to view certain file types, there are other players, and
other file types not covered by these players, but they are probably the most
common. A 28.8K image is blurred and jerky and often freezes while the
audio carries on, but improvements in communications technology should improve
things.
MPEG-4 is a new
international standard from the International Organization for Standardization
(ISO). The MPEG-4 Video (there is
more to the standard than the video part) is closely related to ISO H.263.
There are (at least)
three versions of MPEG-4 for Video for Windows from Microsoft and two versions
from DivX. The most recent Microsoft MPEG-4, as of October 25, 1999, is
Microsoft MPEG-4 Video Codec Version 3, identified by the Four Character
Code
MP43. MPEG-4 Version 3, MP43, Version 2, MP42,
and Version 1, MPG4, are included in the Windows Media Technologies. Specifically, the Windows Media
Tools
contains the Microsoft
MPEG-4 Video Codec Version 3 Application Extension, formerly known as a
Dynamically Linked Library.
"Best" depends on what
the user is trying to do. Selection
of a video codec depends on several variables: time to encode the video, how
widely known and available the video codec is, compression ratios that can be
achieved for a target subjective quality level. The
Performance of AVI
Codecs section gives detailed information on the performance, compression
ratios, video quality, etc. of AVI video codecs.
Cinepak is the most widely used AVI video codec. Cinepak reportedly provides the fastest
playback of video. While Indeo 3.2
provides similar or slightly superior image quality for same compression, Indeo
decompression is much more CPU intensive than Cinepak. Cinepak was originally developed for the
Mac and licensed to Apple by SuperMac.
It is now free with
Video for Windows. It is also free
with Apple's QuickTime.
Summary
Compression reduces your huge video file
to a size that will play properly from CD-ROM or the Web. Since you are going to
lose quality, it is important that you use a dedicated compression tool to get
the best results.
Aspect
Ratio
This is the ratio of the width by the height of a monitor or television screen. Most TVs and monitors have a 4 x 3 aspect ratio. The screens are 4 units wide and 3 units high.
Audio
Gain
Sensitivity of the microphone measured in decibels.
Bandwidth
The amount of data/second that can be delivered across a connection, such as a cable, interface or bus. A 28.8 modem has a bandwidth of 28.8 Kb/second.
Broadcast
A streaming option that sends a single stream that branches down all channels, regardless of whether a client is listening. In relation to Sorenson Broadcaster, broadcast is generally used to mean "streaming."
CD-ROM
Compact Disc--Read Only Memory.
Codec
(coder/decoder
or compression/decompression algorithm) As the name implies, codecs are used to encode
and decode (or compress and decompress) various types of data--particularly
those that would otherwise use up inordinate amounts of disk space, such as
sound and video files. Common codecs include those for converting analog video
signals into compressed video files (such as MPEG) or analog sound signals into
into digitized sound (such as RealAudio). Codecs can be used with either
streaming (live video or audio) or files-based (AVI, WAV) content. When the clip
was encoded some sort of codec was used and you need the same codec in order to
be able to view the clip. The most common codecs are available for download on
the Internet.
Composite
Video
A video stream that combines all the signals required for displaying video into one signal, thus requiring only one connection. NTSC is an example of composite video.
Compression
The act of making a file or data stream smaller. Compression can be either lossy or lossless.
Data
Rate
A measurement of bandwidth. Higher data rate equals more bandwidth. In general, the higher the data rate, the higher the quality of video and/or audio.
Decoding
Reconstructing an encoded file or data stream.
Digitizer
The capture card or device that converts an analog signal into a digital signal. A video digitizer will convert an analog video signal into a digital stream or file.
Encoding
Analyzing and compressing a file or data stream.