QCIF – Quarter CIF. 176×144 pixels; common H.261 and H.263 video resolution.
q signal – one of the two color signals, containing yellow and violet components to which the human eye is relatively insensitive.
quad split – the visual effect of dividing a picture in four segments, each of which may display video from a separate source.
quantization – 1. when converting an analog signal to a digital one, the process is called quantization. It measures a sample to determine a representative numerical value that is then encoded. There are three steps in analog-to-digital conversion sampling, quantizing, and encoding. The representation of the coded values typically is done with binary numbers. Video signals are often coded using 8 or 10 bits, which allow 256 and 1024 different values respectively. Audio uses 16 or 24 bits with 65536 and 16777216 different values. For video and audio coding, increasing the bit number does not increase the maximum or minimum values but the number of steps between minimum and maximum which normally gives a better quality. 2. a function found on sequencers and drum machines that causes notes played at odd times to be “rounded off” to regular rhythmic values. See percentage quantization.
quantization noise – one of the types of error introduced into an analog audio signal by encoding it in digital form. The digital equivalent of tape hiss, quantization noise is caused by the small differences between the actual amplitudes of the points being sampled and the bit resolution of the analog-to-digital converter.
quantized – set up to produce an output in discrete steps.
quartz-halogen – the light of choice in color television, designed to maintain correct color temperature and uniform output throughout its life. Provides much higher output than conventional tungsten light of the same power consumption and has a life up to one hundred times that of common tungsten photographic lights. These lamps are sensitive to shock and handling and should never be touched with bare hands.
quepoint – if you have been working with video editors, you may have come across the word quepoint. Basically, it is point in time where something needs to be happening, either within the video or outside. For instance, quepoints are used by sound studios to do voice-overs. Professional sound editors can pick up quepoints from a video or multimedia presentation and synchronize a recorded voice with the quepoint so that the voice starts talking at the exact moment it should be talking. In short, instead of having to scroll through the timeline to find the right moment in time, you can jump from one quepoint to the other without having to bother about the rest, which is a huge time saver for multimedia professionals. Lately, quepoints are even used in video networks like Viddix. While the video plays, something else shows up on the right hand of the video or even music can start to play when a quepoint passes by in the timeline.
Quicktime – multimedia container (.mov) file format from Apple, is a commonly used file format for video files, running on the Macintosh or under Windows. This versatile format can use several different editing codecs. Popular choices include Apple Prores, Apple Intermediate Codec, and uncompressed. Both Nikon and Canon use Quicktime containers with H.264 codecs to create their camera-original files on the most current cameras. Other manufacturers also use the Quicktime formats but with different codecs. These include Panasonic, Cineform, Avid and Sony. Quicktime enables the creation and playback of Quicktime movies featuring full-motion video, midi tracks and ADPCM audio. It contains one or more tracks, each of which stores a particular type of data, like video, audio, effects, or text (for subtitles, for example). Each track in turn contains track media. This might be either the digitally-encoded media stream (using a specific codec, e.g. JPEG, MP3, DIVX, or PNG) or a data reference to the media stored in another file or elsewhere on a network. An ‘edit list’ indicates what parts of the media to use.
quilting – In digital video footage with strong horizontal and diagonal imagery, an artifact similar to stair steps can appear due to “discontinuities between adjacent DCT blocks.” This artifact is inherent to DCT (Discrete Cosine Transform infra) compressors, which include JPEG and MPEG codecs. DCT compressors process images in 8 x 8 blocks, which do not reproduce smoothly transformed diagonal lines. Enhancing the aperture control on a high-resolution monitor can intensify this artifact, especially in footage with slow camera movement. Video recordings with objects arranged on an approximately 20 degree diagonal plane seem to be particularly affected by this phenomenon. Quilting cannot be remedied.