Quantization Factor applied to DCT coefficients as a part of the process of achieving a required video compression. The coefficients relating to the least noticeable aspects of picture detail - e.g. high frequencies with low amplitude - are progressively reduced so that the final data will fit into the specified data file space. This space is often fixed and relates directly to the quoted compression ratio for I-frame only schemes such as DV. Note that the required quantization will vary according to scene content. Given that too much data would cause problems by overflowing the allotted capacity of the file, compression schemes are cautious and designed to undershoot the file limit. To what extent the files are filled is a measure of the quality of a compression scheme - a reason why the quoted 'compression ratio' does not tell the whole story.
Quantizing The process of sampling an analog waveform to provide packets of digital information to represent the original analog signal. See also: Into digits.
QuickTime QuickTime is a multimedia framework developed by Apple Inc. capable of handling various formats of digital video, media clips, sound, text, animation, music, and several types of interactive panoramic images. Running on either OSX or Windows operating systems, QuickTime supports software packages including iTunes, QuickTime Player and Safari.