Abstract: A terminal configured to receive data from a broadcast station that may simultaneously participate in a wireless network via transmissions to a wireless base station. The terminal determines time periods when data of interest to the terminal will be broadcast and schedules transmissions to the base station to avoid these time periods, thereby avoiding the transmissions preventing reception of the data of interest. The time periods may be determined amongst other means from scheduling information transmitted by the broadcast station.

Abstract: An MPEG decoder (100-180) can use different formats (linear tiled etc) for image data memory (150) for reference pictures when decoding subsequent pictures. Each format brings advantages and disadvantages. The disclosure illustrates that it is possible for different video sequences to have characteristics which match one image buffer format well, but not another, for example where there is a lot of motion or only a little motion between images. Advantageously, the decoder employs a parameterised image buffer format and analysis of the incoming stream and/or measured decoding performance (190) so as to dynamically choose (90, 160, 170) the best image buffer format for the current part of a stream. Cache control features can also be controlled (198) to suit the particular data received.

Abstract: A portable computer device has data acceptance logic (24,40) that determines whether input data items have time and location information. If not, data items are stored together with time and location information taken from clock (30) and location determining circuitry (28), here a Global Positioning Service (GPS) system. A screen (6) is arranged to display data items in a time mode or a space mode. In the time mode, those data items with time information in a time interval are displayed on a time line. In a space mode, data items with time information in a display area are displayed, for example on a map of the display area. The display can be toggled between the time and space modes.

Abstract: A software GPS processing arrangement comprising a FIFO buffer for receiving a stream of the GPS signal samples, a memory, a DMA controller for transferring the GPS signal samples from the FIFO buffer to the memory, a CPU running GPS signal processing software configured to retrieve the GPS signal samples from the memory and process them to obtain a position fix, and a counter operating independently of the DMA controller and the CPU for keeping count of the number of streamed GPS signal samples.

Abstract: A software GPS processing arrangement comprising a FIFO buffer for receiving a stream of the GPS signal samples, a memory, a DMA controller for transferring the GPS signal samples from the FIFO buffer to the memory, a CPU running GPS signal processing software configured to retrieve the GPS signal samples from the memory and process them to obtain a position fix, and a counter operating independently of the DMA controller and the CPU for keeping count of the number of streamed GPS signal samples.

Abstract: Variable length decoding of DCT coefficients in MPEG video data is performed using a standard processor (400) and a small look-up table (LUT 530). The processor performs (520) an integer to floating point conversion on a portion the received bitstream (BS). By this step, lengthy codewords with many leading zeros, which are common in the codebook, are represented in a compressed form by the exponent and mantissa fields (EXP, MAN) of the floating point result (FP). The relevant bits are extracted and used as an index (IX) to address the LUT. This avoids cumbersome bit-oriented logic, while also avoiding a very large LUT that would otherwise be required to represent the same codebook. The entire LUT may thus reside in cache memory (410). In a VLIW processor implementation, decoding of one token is pipelined with the inverse scan and inverse quantisation step of the preceding token(s).

Abstract: Variable length decoding of DCT coefficients in MPEG video data is performed using a standard processor (400) and a small look-up table (LUT 530). The processor performs (520) an integer to floating point conversion on a portion the received bitstream (BS). By this step, lengthy codewords with many leading zeros, which are common in the codebook, are represented in a compressed form by the exponent and mantissa fields (EXP, MAN) of the floating point result (FP). The relevant bits are extracted and used as an index (IX) to address the LUT. This avoids cumbersome bit-oriented logic, while also avoiding a very large LUT that would otherwise be required to represent the same codebook. The entire LUT may thus reside in cache memory (410). In a VLIW processor implementation, decoding of one token is pipelined with the inverse scan and inverse quantisation step of the preceding token(s).

Abstract: A technique for encoding pixel color values for a full or partial digital video image frame has each different color within the image being assigned a color value. The most common one of the colors (0) within the frame or frame segment is identified, and runs of at least three successive pixels of that predominant color are encoded as a first code (00) indicating a run and a second code indicating the run length (LL). Runs of successive pixels having a color (1, 2, 3) other than the predominant color (0) are encoded as successive iterations of a code containing only the respective color value when the run length is less than or equal to a threshold value and as a first code indicating a run (00), a second code indicating a run length (LL), and a third code (CC) identifying the color value when the threshold value is exceeded.

Abstract: In an image processing system for providing two-dimensional pixel images comprised of a purality of polygonal image primitives and a background, the polygonal image primitives representing a three-dimensional object, a Z buffer and a color buffer are cleared by the steps of rendering image primitives relating to foreground in the color buffer (354) and the Z buffer (353); and subsequently scanning the Z buffer and for each pixel, if the Z value is a predetermined background value such as zero (357), clearing the corresponding location in the color buffer to background color (358), and if the Z value is not the predetermined background value, clearing the Z buffer to that predetermined background value (359). In the method, either a Z buffer or a color value is written during the buffer clearing process, but never both. The pixels may be read from cache in groups, the size of a group being selected to maximize the possibility of all consecutive pixels in a group being either foreground or background pixels.

Abstract: A method is described of encoding pixel color values for a digital video image frame in which each different color within the image is assigned a color value. A predominant color is identified for the image frame and, in a first embodiment (FIG. 5), each pixel having a color other than the predominant color is separately coded as its respective color value (0010 to 1111), with runs of three or more successive pixels of the predominant color being run-length encoded. A further code (0000 0011 cccc), similar in arrangement to that indicating a run, is provided to allow a change in the specified predominant color during the course of a frame. In a further embodiment, runs of all colors are run-length encoded but with a shorter coding scheme for runs of the predominant color or, in a still further embodiment, a small range of predominant colors. A principle use for these coding schemes is to improve efficiency of coding for certain classes of image material.

Abstract: Texture mapping or video mapping is performed in such a way as to obtain perspectively correct images, while at the same time not requiring excessive computational overheads. Non-linear functions required to achieve perspectively correct images are stored in the form of look-up tables. Depth extents at the extremes of a locus of interpolation are compared and from this comparison a particular look-up table, or a pair of look-up tables, are selected. When a pair of look-up tables are selected, it is possible to linearly interpolate between the two, in order to obtain a closer approximation to the desired non-linear response.

Abstract: A method and apparatus are described for generating images from assembled polygonal image primitives. As a precursor to rendering, an ordered list of the primitives is assembled with degenerate cases being identified and discarded. Following removal of the degenerate cases, the remaining primitives undergo a series of tests to identify special cases whereby account can be taken of the rendering technique of omitting the right hand pixel of a span and bottom span of a primitive to simplify the rendering operation.

Abstract: In an image source for multimedia applications such as networked computer games, a graphics engine (16) generates pixel images one line at a time using a scan-line algorithm and supplies the generated scan lines to an encoder (18) where they are buffered. The encoder codes the buffered pixel data as macroblocks of, for example 16.times.16 pixels according to MPEG or similar standards. When the graphics engine has sent sufficient scan lines for a first macroblock to the encoder, it sends a signal (FLAG) on receipt of which the encoder begins coding the pixel data as a macroblock in a line of macroblocks whilst continuing to receive scan lines from the graphics engine (16). To increase encoder efficiency, the graphics engine specifies to the encoder global (GMV) and macroblock (BMV) motion vectors for substantially all or selected ones of the macroblocks of an image respectively.

Abstract: A 3-D image synthesis apparatus maintains an "object database" (OBJ) defining a 3-D world to be represented on a 2-D display screen (DIS). The object database includes light sources (LS) which have non-uniform distributions of illumination. To simplify calculations of the illumination of an object surface (P.sub.O), the apparatus pre-stores (606) one or more look-up tables. The look-up table (606) is then addressed by polar coordinates (.theta.,.phi.) calculated per pixel of the output image, to incorporate the dependency of illumination on direction. Several tables may be stored for each light source, each representing the illumination pattern at a different distance (D) from the light source. Smooth variations can be achieved by interpolation between integer values of .theta.,.phi. and D.

Abstract: A method and apparatus are disclosed for the coding of digital images for subsequent display by an apparatus having multiple image planes, wherein each image plane provides a unique information density. Accordingly, when an image feature is to be encoded, a determination is made as to whether it is possible to encode the image feature in a relatively lower density image plane or whether the feature must be encoded in a higher density image plane. A decoding system is likewise provided to interpret the encoded information for display on a display apparatus having multiple image planes.

Abstract: An image processing method and apparatus are described for polygon rendering in two dimensional screen space, where the rendering includes mapping of texels from a texture map onto pixels within the polygon. The texture map (18) holds fewer texels than would be required to render a full screen of pixels, or even a large polygon, and the rendering process is carried out in a sequence of rendering windows overlying successive areas of a polygon, with the texture memory (18) being refreshed from mass storage (12) as required between windows. Storage (20) is provided for calculated polygon edge data to enable continuous edges to be maintained over two or more rendering windows to avoid discontinuity effects.

Abstract: A method and apparatus are provided to enable variable speed play of motion-prediction coded sequences of video signal frames. Prior to encoding, input image frames (S1,S2) are reduced in size with further image frames (M1,M2) being formed, each including two or more of the spatially reduced input image frames. Following decoding of the motion-prediction coded sequence of further image frames, display image update rates greater than the image decoding rate by a factor determined by the ratio of input sequence frames to a further image frame may be achieved. Particular applications of the method and apparatus are in interactive display systems where image update rates may be varied under user control.

Abstract: Moving output images are presented to a two dimensional display, such as a conventional television receiver (26). Three video sources are read from a compact disc, a notional front image and a notional back image being in the form of CD-I A and B planes. A notional back plane is a full frame, full video rate image, read from the disc as a coded MPEG data stream. After decoding, each pixel of each image includes depth data and opacity data. It is thus possible for an image in the notional front or notional middle plane to pass behind an object in the notional back plane. The depth and opacity data is severely compressed for the MPEG stream, by a process of quantisation and run-length encoding. The low resolution depth values for each pixel are converted to high resolution depth values via a look up table in order to further define the depth of each notional plane.

Abstract: A logic processor-controlled data display apparatus having a display memory in which pixel data representing text for display is stored in bit-map form. The pixel data is produced for each display from character data stored in a background memory. When the character data is stored in bit-map form it can be read directly from the background memory bit-by-bit and written into the display memory as the pixel data. However, this process takes a large number of programme steps, so that the transfer of the data is relatively stow. The present invention provides for the storage in the background memory of character data in the form of machine code sub-routines. The sub-routine for a character contains instructions for identifying the shape-defining pixels (dots) of the character relative to a base dot position and the sub-routine is run to write these pixels into the display memory following location of the base dot position in the display memory.

Abstract: A method of generating a two-dimensional image representing a three-dimensional scene is describerd. The method comprises: (a) storing a set of foreground pixel data and at least one set of background pixel data, each such set defining a color and a depth for each pixel of the image; (b) selectively modifying the stored foreground and background data in response to a series of input pixel data defining color and depth for a series of pixels of the image; and (c) forming output pixel data by combining the stored foreground and background color for each pixel in proportions defined by a mixing value associated with that pixel.