(Audio Video Interleaved) - Windows
format for saving video with sound. Sometimes used for
media files on CDs (1X to 4X CD-Rom speeds).
width of the band over which frequencies can be
transmitted. So what's a band? A band is a portion of
the electromagnetic spectrum, defined by the lowest
and highest frequencies in it. The bandwidth is the
difference between the highest and lowest frequencies.
The greater the bandwidth, the greater the carrying
capacity. Maximum bandwidth is determined by your
internet connection speed (Mbps). The actual
bandwidth is a factor of the maximum bandwidth
and the amount of network traffic at that moment. You
can test the bandwidth available at your site at
the Internet connection speed test center.
ancient codec that produces large files. Still used
for 24-bit video
intended for CD-ROM. This codec attains higher compression
ratios and faster playback speeds than the Apple Video
codec. You can set the
data rate for playback; picture quality drops more noticeably at data rates
below 30 KBps.
software package that provides a graphic-user interface for
applying a variety of compression/decompression algorithms.
Cleaner is the industry standard for video compression.
mathematical algorithm that COmpresses/
digital video. These codecs are usually applied by a
specialized software application such as Cleaner or
process that reduces the file size (number of bytes,
KB, MB) required to store or transmit digital
video. Most compression methods either compare data
between frames or eliminate inter-frame or
intra-frame redundancies. The compression may be done
by software, hardware or a combination of the two. The
data is decompressed during playback on the client
machine. So the user must have access to the codec
used through some plug-in or player on the client
- In digital video,
when the computer cannot keep pace with the displayed
images, it drops frames in an attempt to catch up.
This can occur when the hard drive does not have
sufficient room to write the file in one continuous
sweep (frames can be dropped between sectors).
files that can be used or executed by computers
with different operating systems. For example, FLASH ,
a a vector animation program, can produce media files
that can play on both Macintosh and
Windows computers. Windows
Media Technology is not always cross-platform.
- (NTSC or PAL), A Lossless codec used by
digital video cameras and on DVDs. In DV, every
frame is a key frame so the files are large but very
Start. See Progressive Download.
per second (FPS) -The
number of picture images (frames) displayed per second
in a media file. FPS gives digital video the illusion
of motion. Full-motion video, such as analog video,
with no dropped frames, is considered 30 FPS (NTSC
number of images per second displayed in a stream of
The amount of motion in a video is either considered high or
low. High motion can be produced by objects moving across
the field, as well as changes in camera angles, zooming in
on an object, fading in or out or other transitions.
codecs register what information changes between frames. If
a several frames in the video have the same blue sky with no
changes (clouds, birds, etc), then this information does not have
to be represented in the data for every frame. It is only
represented in keyframes or when there is a change to the data.
.JPEG (Joint Photographic Experts Group)
compressed, still-image graphics files. There are two
major types of JPEG - progressive, where a fuzzy
images emerges into 100% decompression/clarity, and
baseline or standard, where a clear image is revealed,
part-wise, top-down. Progressive, or interleaved,
decompression looks better over networks.
codecs compress large picture files and simple jpg
a complete video frame that contains
all the graphic information, not just the changes from
the previous frame. If you reduce the number of
key frames you will also have a smaller file but sometimes the
video looks like the audio is no longer synchronized. The
number of key frames is set by picking a key frame every #
of frames, so reducing the number of key frames is performed by
increasing the number. For example, a key frame every 20
frames has fewer key frames than a key frame every 10
A compression method that makes every frame a keyframe.
The data within the frame is compressed. For
example, if an entire wall is the same color that data
can be compressed into a smaller number of
- A compression method which, to save space, does NOT contain
all the original video information. Lossy compression
reduces data by describing only interframe changes. The user
must specify the number of frames per second and the number of
frames between each keyframe.
(high-end, modem or standard)
(Motion Picture Experts Group) - creators of
both hardware and software codecs for video files. MPEG
1 and 2 codecs still generate
large file sizes, so MPEG is best suited for CD-ROM,
NTSC or PAL, applications. MPEG 4 is the new
standard for inter-operable files although not all browser
plug-ins are compatible yet.
- An audio codec for music that produces small files for a broad
range of instruments and voice. It is also good for voices
that have a slurred or musical quality.
1. MPEG1 - 1/4
broadcast quality translating to 352x240pixels.
2. MPEG2 -
Full-motion quality translating to 704x480 pixels
and 30 (broadcast-quality video).
is no MPEG 3
4 has finished beta testing. WOW! Small file sizes,
brillant color and high motion. Can it get better
The number of dots, or points of color that are the unit of
measurement for video. For example, a video clip can be 240
x 180, 360 x 240, 800 x 600, etc. The most common ratio for
video clips is 4:3 (width to height).
Download - Also called Fast Start. A file
configuration that allows the client machine to start playing the
file before it is fully downloaded from the server. Files
are configured for Progressive Download during the compression
process when using Cleaner.
- A file format commonly used in video. QuickTime
was developed by Apple by is truly cross-platform. QuickTime files
can be served by a Real Time Streaming Protocol server or a web
server that has been coded for Fast Start (also called Progressive
Pro - A
software program available from Apple that provides a graphic user
interface for video, audio and animation compression as well as
minor video and audio editing. QT Pro is cross-platform.
Time Streaming Protocol - A server format that provides
files in real-time. This format discourages downloading
files but disruptions in the web cause lost data.
- A file format commonly used in video and
audio. Based on the QuickTime architecture
and truly cross-platform. RealMedia files can be
served by a Real Time Streaming Protocol server or a
web server that has been coded for Fast Start (also
called Progressive Download). RealMedia is a
proprietary format (not open source like QuickTime) so
files in this format can not be converted to other
The frequency at which audio is sampled for
Video - A video codec that
produces high quality files for either CD-ROM or
web video. Similar to the Cinepak codec,
Sorenson Video can produce high quality at data rates under 200
KBps. Although this codec is
capable of better picture
quality and creates smaller files than
requires more compression time.
(audio or video) -
A file format commonly used in video and audio.
Developed by Microsoft and finally
cross-platform. Many streaming radio stations on
the web use Windows Media format (such as National
Public Radio). Files can be served by a Real
Time Streaming Protocol server or a web server that
has been coded for Fast Start (also called Progressive
Download). Windows Media is a proprietary format
(not open source like QuickTime) so files in this
format can not be converted to other file types.