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Tektronix provides test and measurement instruments, solutions and services for the computer, semiconductor, military/aerospace, consumer electronics and education industries worldwide.
Standardised video systems currently exist employing the following number of total lines per frame: 525, 625, 1125.
Furthermore, each of these operates in a 2:1 interlace mode, with 262.5, 312.5, 562.5 lines per field (with concurrent temporal differences at field rates of 50.00, 59.94, or 60.00 fields per second). Additional systems are being proposed. While simple transcoding by deletion or repetition can be applied, it is more commonly done by applying an algorithm to stored information in order to generate predictive line structures in the target system.
Industry:Software
A) Picture defects that appear only when there is motion in the scene. Interlaced scanning has motion artefacts in both the vertical and horizontal directions. There is a halving of vertical resolution at certain rates of vertical motion (when the detail in one field appears in the position of the next field one sixtieth of a second later), and horizontally moving vertical edges become segmented (reduced in resolution) by the sequential fields. This is most apparent when a frame of a motion sequence is frozen and the two fields flash different information. All subsampling ATV schemes have some form of motion artifact, from twinkling detail to dramatic differences between static and dynamic resolutions. Line doubling schemes and advanced encoders and decoders can have motion artifacts, depending on how they are implemented. Techniques for avoiding motion artefacts include median filtering and motion adaptation or compensation.
b) In all temporally-sampled systems (i.e., both photographic and electronic), realistic motion reproduction is achieved only with sampling above the Nyquist limit. The subjective response to motion artefacts is complex, influences by the various degrees of smoothing and strobing affecting temporal and spatial resolution, integration and tag in the sensing, recording, and display elements; sampling geometry and scanning patterns; shutter transmission ratio; perceptual tolerances, etc. (Motion appears “normal” only when significant frame-to-frame displacement occurs at less than half the frame rate; i.e., “significant motion” distributed over at least two frames.) Motion artefacts most frequently observed have their origins in the following: image components with velocity functions extending beyond the Nyquist limit (such as rotating, spoked wheels), motion samples with such short exposures there is noticeable frame-to-frame separation of sharply defined images (such as synchronised flash illumination), asynchronous sampling of intermittent motion (such as frame-rate conversions). A considerable number of motion artefacts appear so frequently as to be accepted by most viewers.
Industry:Software
A) Coding techniques which involve separating the signal into segments which have changed significantly from the previous frame and segments which have not changed. b) Data reduction based on coding the differences between a prediction of the data and the actual data. Motion compensated prediction is typically used, based on reference frames in the past and the future.
Industry:Software
Packets of “stuffing” that carry no data but are necessary to maintain a constant bit rate with a variable payload. Null packets always have a PID of 8191 (all 1s).
Industry:Software
A memory buffer which stores a single digital video line. One application for line stores is use with video filtering algorithms or video compression applications.
Industry:Software
In MPEG, the use of motion vectors to improve the efficiency of the prediction of pel values. The prediction uses motion vectors to provide offsets into the past and/or future reference pictures containing previously decoded pel values that are used to form the prediction error signal. The book Motion analysis for Image Sequence Coding by G. Tziritas and C. Labit documents the technical advances made through the years in dealing with motion in image sequences.
Industry:Software
A form of compression in which the codec compresses the data within one frame relative to others. These relative frames are called delta frames. See Delta Frame, Key Frame. Compare Intraframe Compression.
Industry:Software
Sprocketed base with a magnetic coating for audio recording and playback.
Industry:Software
The ability to see scanning lines. Seeing them makes it harder to see the image (like looking out a window through venetian blinds or not being able to see the forest for the trees). Some ATV schemes propose blurring the boundary between scanning lines for this reason.
Industry:Software
The process of determining changes in video object positions from one video frame to the next. Object position determination is used extensively in high-compression applications. For instance if the background of a scene does not change but the position of an object in the foreground does, it is advantageous to just transmit the new position of the object rather then the background or foreground. This technology is used in MPEG, H.261, and H.263 compression.
Industry:Software
