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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.
In the archetypal hybrid coder, an estimate of the next frame to be processed is formed from the current frame and the difference is then encoded by some purely intraframe mechanism. In recent years, the most attention has been paid to the motion-compensated DCT coder where the estimate is formed by a two-dimensional warp of the previous frame and the difference is encoded using a block transform (the Discrete Cosine Transform). This system is the basis for international standards for videotelephony, is used for some hdtv demonstrations, and is the prototype from which mpeg was designed. Its utility has been demonstrated for video sequence, and the DCT concentrates the remaining energy into a small number of transform coefficients that can be quantized and compactly represented. The key feature of this coder is the presence of a complete decoder within it. The difference between the current frame as represented as the receiver and the incoming frame is processed. In the basis design, therefore, the receiver must track the transmitter precisely, the decoder at the receiver and the decoder at the transmitter must match. The system is sensitive to channel errors and does not permit random access. However, it is on the order of three to four times as efficient as one that uses no prediction. In practice, this coder is modified to suit specific application. The standard telephony model uses a forced update of the decoded frame so that channel errors do not propagate. When a participant enters the conversation late or alternates between image sources, residual errors die out and a clear image is obtained after a few frames. Similar techniques are used in versions of this coder being developed for direct satellite television broadcasting.
Industry:Entertainment
A television system that offers picture quality substantially improved over conventional receivers, for signals originated in standard 525-line or 625-line format, by processing that involves the use of field store and/or frame store (memory) techniques at the receiver . One example is the use of field or frame memory to implement de-interlacing at the receiver in order to reduce interline twitter compared to that of an interlaced display . IDTV techniques are implemented entirely at the receiver and involve no change to picture origination equipment and no change to emission standards.
Industry:Entertainment
The fineness or coarseness of an image as it was digitized, measured in Dots Per Inch (DPI), typically from 200 to 400 DPI.
Industry:Entertainment
The fusion of video and computer technology. A video program and a computer program running in tandem under the control of the user. In interactive video, the user's actions, choices, and decisions affect the way in which the program unfolds.
Industry:Entertainment
A system developed for television which divides each video frame into two fields. This is done by first drawing one field consisting of an image's odd scan lines (1, 3, 5...525) and then drawing the remaining even scan lines (2, 4, 6...), interweaving both fields. Interlacing reduces the perception of screen flicker. Interlacing can cause annoying effects with images such as computer generated text and graphics when transferred to video.
Industry:Entertainment
A CCITT term for a relatively new telecommunications service package. ISDN is basically the telephone network turned all-digital end to end, using existing switches and wiring (for the most part) upgraded so that the basic call is a 64 kbps end-to-end channel, with bit-diddling as needed (but not when not needed!). Packet and maybe frame modes are thrown in for good measure, too, in some places. It's offered by local telephone companies, but most readily in Australia, France, Japan, and Singapore, with the UK and Germany somewhat behind, and USA availability rather spotty. A Basic Rate Interface (BRI) is two 64K bearer ("B") channels and a single delta ("D") channel. The B channels are used for voice or data, and the D channel is used for signaling and/or X.25 packet networking. This is the variety most likely to be found in residential service. Another flavor of ISDN is Primary Rate Interface (PRI). Inside the US, this consists of 24 channels, usually divided into 23 B channels and 1 D channel, and runs over the same physical interface as T1. Outside of the US then PRI has 31 user channels, usually divided into 30 B channels and 1 D channel. It is typically used for connections such as one between a PBX and a CO or IXC.
Industry:Entertainment
A video frame in which all of the video information is recorded in compressed fashion. If the clip has a large amount of motion, better playback will occur with every frame being a Key Frame. If there is very little motion, such as a narrator, a higher number of Delta Frames will give satisfactory playback.
Industry:Entertainment
The process of replacing part of one video image with video from another image. As opposed to mixing images together, keying "cuts" one image cleanly into another.
Industry:Entertainment
A television system that limits the recording or transmission of useful picture information to about three-quarters of the available vertical picture height of the distribution format (e.g. 525-line) in order to offer program material that has a wide picture aspect ratio.
Industry:Entertainment
The layout of audio and video scenes in a continuous length of tape. Working with linear video is slower than with non-linear footage, because the operator must fast forward or rewind to search for scenes.
Industry:Entertainment
