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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 video telephony, 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 basic 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 the 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:Software
A bit-mapped graphics file format popular for storing lower resolution image data.
Industry:Software
Combining nonlinear edited video files with linear (deckto- deck) segments of footage.
Industry:Software
A computer interface that allows the user to perform tasks by pointing to icons or graphic objects on the screen.
Windows is a graphics user interface. Most multimedia programs require GUIs.
Industry:Software
The printed circuit board within a workstation that contains the graphics processors.
Industry:Software
A combination of wavelet and transform algorithms within the same compression technology.
Industry:Software
A nonselective (color neutral) diffuse reflector intended to be lighted by the normal illumination of the original scene, and having a reflectance factor of 18% (compared with a perfect reflector at 100% and prepared magnesium oxide at 98%). The gray card luminance is used as a guide in determining scene exposure so that the image is placed upon the most favorable portion of the transfer function curve.
Industry:Software
A directional pickup pattern where maximum discrimination occurs at more than 90 and less than 180 degrees off axis.
Industry:Software
a) The luminance portion of the video signal. A scale of 10 from TV black to TV white indicating the shades of gray a camera can see at any one time and to which a camera can be adjusted. A gray scale adjustment of 7 is good. b) An optical pattern in discrete steps between light and dark. Note: A gray scale with ten steps is usually included in resolution test charts.
Industry:Software
