Category Archives: Q

Quantel

Apt name for the world leaders in digital television equipment – abbreviated from QUANtized TELevision. Quantel has over 40 years’ experience of digital television techniques – significantly more than any other manufacturer.

Quantization

Factor applied to DCT coefficients as a part of the process of achieving a required amount of 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.

Quantum dot (QD)

Quantum dot is a relatively new display technology for television screens. QD are microscopic particles that emit light when electricity is applied, or when light is shone on them. The light’s color is very stable and relates to the QD’s size. Of late, they have been applied to screen technology in two ways.

One is to use them as a backlight for LCD screens. Currently LED screens use LEDs as the backlight, and an LCD filter to control the brightness of each screen ‘dot’ (not quantum!). QD backlight uses just a blue LED light which is converted by QDs to reasonably pure red and green – very close to the required red, blue and green – so far less light is absorbed in the RGB filters behind the LCD screen, so providing more useful light (brighter pictures) and more accurate colors, and it does not drift.

The other type of QD screen uses QD-based LEDs to directly emit the screen light – as OLEDs screens do now. However OLED screens remain at high prices and there is some fear of quality degradation over time. QD-LED color can be accurately tuned in manufacture and is has a narrow spectrum. It does not drift and is not known to degrade. Amazon’s Kindle Fire HDX tablet uses QD technology, as did Sony in 2013 with its Triluminous screens.

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.

See also: ProRes