Televerket

Telefonaktiebolaget Lm Ericsson (Publ)

Harald Brusewitz

Bo Burman

Göran Roth

Goran Roth

G&ouml;ran Roth

Method and apparatus for decoding a compressed video signal having a first resolution for use by a display unit having a second resolution. The method and apparatus involve downscaling the compressed video bit stream before the bit stream is decoded, which results in a considerable decrease in decoding complexity requiring less memory and lower CPU power usage.

Low complexity video decoding

An improved imaging system and method for providing increased viewer control over the operating parameters of the imaging system is described. Viewer control is facilitated by including a backchannel within the imaging system, whereby a viewer may adjust spatial and temporal resolution, quantization and other operating parameters of the video transmission.

Imaging system and method for interactive control of image quality

An imaging system and method for alleviating perceptional problems of a viewer during the transmission and display of high resolution still images on a video system is disclosed. Through modifications to an encoder and decoder within the imaging system, the viewer may select a still image or portion thereof from a video image sequence for viewing. The imaging system and method ameliorate perceptional delays in displaying the lengthy high resolution still image by immediately displaying a lower-resolution, shorter-length video image frame corresponding to the still image. The lower resolution video image being displayed is then updated and refined with the image data from the high resolution still image as it is received.

Motion and still video picture transmission and display

A method and device for image coding, primarily intended to be applied in the transmission of video signals, convert a video signal to a bit stream by coding and quantising. The bit stream is stored in a buffer store before it is sent at a constant bit rate on a transmission line. The content in the buffer store is regulated by varying the step height in the quantiser. With the frame rate at the input being known and the frame rate and bit rate at the output being known, the ideal buffer store content can be determined. The actual buffer store content is sensed and compared with the ideal buffer store content and the difference between these two values is determined. The step height in the quantiser is adjusted as a function of the difference.

Video coding system with buffer control quantization step size

A method of motion compensation and elastic deformation in picture sequences in transmission of moving pictures between a transmitter and a receiver, that is a picture coding method in which the pixel values of the picture are determined using a previous picture. In the transmitter, each picture in the picture sequence is divided into triangles by suitably choosing corner points, and the motion between two successive pictures is estimated such that the motion vectors of all the corner points can be established. Information about the corner points and/or the motion vectors is transmitted from the transmitter to the receiver, in which the motion vectors of the internal points of the triangles are calculated using the three transmitted motion vectors belonging to the respective triangle. The pixel values in the corner points of the triangles and in the internal points of the triangles are calculated using the transmitted and the calculated motion vectors, respectively. Preferrably, the motion vectors of the internal points of the triangles are calculated by interpolation.

Method of motion compensation and elastic deformation in picture

The invention relates to a method of moving a pixel a subpixel distance and is intended to be applied in picture coding methods to determine the value of a pixel located between the fixed pixels on the screen. The pixel value is calculated using a known motion vector and the pixel values located in the vicinity of the corresponding pixel in the previous picture. According to the invention at least 3.times.3 pixels from the previous picture are used and the pixel value is calculated as a sum of the previous pixel values weighted by coefficients depending of the motion vector. The coefficients are preferrably calculated as polynomials of the subpixel part of the motion vector.

Method of moving a pixel a subpixel distance

The invention relates to a method of recovering lost bits in digital transmission. The invention can be applied in ATM networks or networks in which the receiver utilizes soft decoding. A number of data bits dl-dn are transmitted together with a number of control bits cl-ck. The control bits are calculated in the transmitter using a number of parity constants pll-pkn such that a corresponding number of parity relations are fulfilled. In the receiver, the positions of the lost data bits are detected and a number of syndrome bits sl-sk are calculated from the transmitted data bits and control bits. Then the lost data bits can be recovered by mapping syndrome bits indicating the values of the lost data bits. By using the knowledge about the positions of the lost data bits a reduced number of control bits are required compared with the prior art.

Method of recovering lost bits in a digital transmission

The invention relates to a method and a device for image coding having a particular, but not necessarily an exclusive, application in the transmission of video signals. The video signal is converted to a bit stream by coding and quantising and stored in a buffer store before it is transmitted on a transmission line at a constant bit rate. Problems experienced with the known technology have been the prevention of overflow in the buffer store and the buffer store being emptied prematurely. Both of these problems give rise to a deterioration in image quality. At the same time, the content of the buffer store should be as small as possible. According to the invention, not all the frames are coded and transmitted, but a certain number (k) of frames are skipped between each coded frame. The number k is based on the transmission rate R, the frame rate fo of the video signal and minimum value (bR/fo) set for the content of the buffer store. The number of skipped frames is selected so that the buffer store is not emptied below the set lower limit before the next frame is coded. The buffer store content is also regulated by skipping or setting to zero certain components in the bit stream from the coder core. The actual and ideal buffer store contents are determined and selected components of the bit stream are set to zero in dependence on the difference between the actual and the ideal content values. The invention also relates to a device for carrying out the method. The device is preferably constructed as a VLSI circuit.

Method and a device for image coding

A method and a device are disclosed for variable length coding and decoding of an information block of input signals, with the information being concentrated at the beginning of the block and the block being terminated by a continuous succession of zero words. Two code trees are utilized for coding and decoding the block. The first of the code trees is utilized for coding and decoding the first part of the block up to and including the word before the last non-zero and an end of the block character EOB, and the second code tree is specially designed for coding and decoding the last non-zero word. A switching device provides for switching between the two code trees and associated devices after the character EOB and before the last non-zero word.

Method and means for variable length coding

A method and apparatus for coding and decoding picture information is described. According to prior art two modes, are utilized for transmitting picture information, respectively. According to the present invention advantages are obtained in using a mixed mode, i.e. certain frequency components are transmitted with prediction and the remaining components without. In the invention two channels, with and without prediction, are utilized respectively. These channels are selectively connected by means of switches, which are controlled by a control means.

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Alvsjo, Sweden

Harald Brusewitz