time compression - Computer Definition
- A compression technique that speeds up the playback of audio and audio-video content. Linear time compression does so by uniformly compressing and speeding up the playback of all speech segments, but can affect the pitch of the speech. Non-linear time compression does so without affecting the pitch, by selectively speeding up certain speech segments, eliminating or reducing pauses and periods of silence, and uniformly speeding up the remaining speech. More sophisticated approaches attempt to mimic the human compression strategies that people use when they talk faster.Time compression, both linear and non-linear, has been used for some years in voice mail systems, and more recently in streaming media products used in Web-based applications. See also compression and voice mail.
- A compression technique that supports the transfer of data between devices at a rate faster than the playback rate, depending on bandwidth availability. For example, a 30-frame file of 56.7 Mbits that represents 1 second of broadcast-quality video in raw, uncompressed content form might blow up to 65+ Mbits to accommodate overhead.The transmission of that file in real time, i.e., 30 frames per second (fps) to create the illusion of full motion for a human input device (eyeball) and processor (brain) would require a transmission facility capable of a rate of 65 Mbps to support that one audiovisual signal. If, on the other hand, one can compress that content by 90%, the file is 5.67 Mbits of raw content and 6.5 Mbits, including overhead. If the transmission facility is capable of the same 65 Mbps and the content is stored and ready for transmission, 1 second of real-time content can be transmitted from source to sink in one-tenth of a second.The if transmission facility is an OC-192 backbone SDH/SONET fiber optic transmission system (FOTS) running at 10 Gbps in the carrier backbone, then 1,538 seconds (25.64 hours) of full-motion video theoretically can be transmitted in one second. Ultimately, of course, the slowest link determines the maximum speed of transmission, end-to-end, and, therefore, whether or not even the most sophisticated compression technique yields the benefits of time compression. See also backbone, bandwidth, broadcast quality, compression, FOTS, overhead, persistence of vision, phi phenomenon, real time, SDH, and SONET.