Glossary of Multimedia Terms

Analog-to-Digital Converter: A chip that takes an analog signal (like NTSC video) and converts it into a digital signal. These converters are used on captures cards.

Bandwidth: The amount of information that can be sent and processed in a certain amount of time over networks. Digital video requires a high bandwidth rate.

Cinepak: The codec allows temporal and spatial compression. It is a codec primarily used for CD-ROM video compression or for WWW compression.

Codec: A codec is a compression/decompression software component which translates video or audio between its uncompressed form and the compressed form in which it is stored. Examples of codecs include Cinepak, Video, QuickTime.

Color-depth: This refers to the range of colors that can be used in a movie or an image. The higher the color-depth, the larger the file size.

  • Gray scale: black, white & shades of gray (8-bit)
  • 256-color (8-bit)
  • Thousands of colors (16-bit)
  • Millions of colors (24-bit)

Compression: Temporal compression compacts the changes during a sequence of frames by looking for patterns & repetition over time. Spational compression looks for ways to compact a single frame by looking for patterns or repetition among pixels - this is primarily used for animation.

Data rate: The amount of information per second used to represent a movie expressed in KBps. A double speed CD-ROM movie is usually made at a data rate of 167 KBps. The data rate of uncompressed NTSC video is about 27 Megabytes per second. One thing to note is that if the data rate is faster than your Internet connection or CD-ROM, then palyback will be choppy.

Data Rate Limiting: The ability of a program or a codec to control the size of a compressed movie so that it meets the specified data rate.

DVD: This acronym originally stood for "Digital Video Disc." Today, it is usually made in reference to DVD-ROM

or DVD-Video.

DVD-ROM: A version of the DVD disc format for computers which may eventually replace CD-ROM's.

DVD-Video: A version of DVD disc format that will be used for storage of prerecorded movies and should replace VHS. DVD-Video uses MPEG.

Fast-start: A progressive download feature of QuickTime which allows movies to be viewed while they are being downloaded.

Flattening: A final pass applied to a compressed movie, which ensures that the movie data is laid out in a completely linear fashion. It also makes sure the audio is interleaved properly with the video.

fps: Frames Per Second.

Frame Rate: The number of frames per second in a movie. NTSC video run at 30 fps, film runs at 24 fps, digital video for the web may run between 15 fps and 30 fps.

Indeo: A codec developed by Intel. It allows temporal and spatial compression as well as data rate limiting. Used mostly for CD-ROM projects.

kps: KiloBytes per second. A unit of data rate measurements. A kilobit is 1/8th the size of a kilobyte.

Keyframe: The complete video image which is the basis for compression.

kHz: kiloHertz are the number of audio samples per second. Higher sample rates have better sound quality, but the trade-off is a larger file size.

Noise: A distortion in a signal. In audio, noise causes the track to "hiss".

NTSC: Video format used by the United States and other countries that runs at 29.97 (30) frames per second.

PAL: Video format used by European countries that runs at 25 frames per second.

Progressive Download: Progressive download video files permit the user to begin viewing the movie before it has been completely downloaded.

Streaming: Streaming audio and video refers to data that is transferred in real-time. Files are no downloaded to the user's computer, but are "streamed" from the server to the user's machine.

WYSIWYG: What You See Is What You Get. Acronym meaning that what you see on the computer screen is what you will get for you final output.

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Updated 15 Aug 99, esp