Abstract: The invention features furnishing a representation of the quadrature amplitude modulation of two input signals (e.g., U and V video signals) based on the phase of a reference signal (e.g., a color burst reference signal). The two input signals are scaled based on the phase of the reference signal, and the scaling is synchronized to the phase of the reference signal.

Abstract: A method and apparatus for extending secure communication operations via shared lists is accomplished by creating a shared list in accordance with authorization parameters by one user and subsequently accessing the shared list via the authorization parameters by this and other users. To create the list, a user within the secured communication system determines whether it has been enabled, or authorized, to create a shared list. If so, the user identifies at least one other user to be added to the shared list. Having identified another user, the user creating the shared list verifies that the secure communication parameters (which includes a public key certificate of an end-user or of a certification authority) it has received regarding the another user is trustworthy. If the secure communication parameters are identified as trustworthy, the secure communication parameters of the another user are added to the shared list. To authenticate the shared list, the user creating the list digitally signs it.

Abstract: A method and apparatus for determining the level of detail for texture mapping applications in video graphic circuits begins by updating first and second linear components of a set of derivatives when rendering a pixel of an object in a given scan line. The first and second linear components are updated in a linear manner based on first and second increment values, respectively. The set of derivatives corresponds the changes of the texture coordinates with the changes of the physical coordinates of an object being rendered, the derivatives include .delta.s/.delta.x, .delta.t/.delta.x, .delta.s/.delta.y, and .delta.t/.delta.y--in general, the set of derivatives equals .delta.a/.delta.b=w.sup.2 *((1/w)*(.delta.(a/w)/.delta.b-(a/w)*(.delta.(1/w)/.delta.b))). When the object is being rendered on a new scan line, third and fourth linear components are updated in a linear manner based on third and fourth increment values, respectively.

Abstract: The invention features a method and apparatus for use with a computer system having a memory and a bus (e.g., a PCI bus). The bus is monitored for detection of a bus cycle intended for a controller (e.g., a DMA controller) used to transfer data between a bus device and the memory. After detection, the bus device is used to claim the bus cycle and to emulate the response of the controller to the bus cycle.

Abstract: A method and apparatus for controlling contrast of images when displayed on a monitor begins when signals corresponding to an image and a contrast feedback signal are received. The signals are mixed with the contrast feedback signal to produce image output signals. The contrast feedback signal is, in turn, determined based on the contrast level of the image output signals. As such, a closed loop feedback circuit is provided to control the contrast levels of the image output signals.

Abstract: A method and apparatus for mapping a linear address to a tiled address that reduces latency between retrieval of pages of data is accomplished when a video graphics processor receives a linear address from the central processing unit and determines whether the linear address is referencing a tiled surface, which is one of up to four portions of the memory. If so, the video graphics processor obtains parameters of the tiled surface. Having obtained the parameters, the video graphics processor determines a normalized linear address based on at least one of the parameters and the linear address. Having done this, the video graphics processor determines a band pointer of the tiled surface based on at least one of the parameters, the normalized linear address and a modular function. In essence, the band pointer points to a normalized initial address of a band of a tiled surface, which includes a plurality of bands.

Abstract: A method for producing a modified cursor in a video graphics display system is accomplished by receiving data corresponding to the modified cursor and comparing the received data with cached cursor information. If the comparison produces a favorable result, a pointer is stored in a cursor offset register, where the pointer corresponds to a data set in video memory that describes the modified cursor in a video format. When the comparison produces an unfavorable result, a video format data set is generated for the modified cursor and is stored in the video memory. A pointer to the new video format data set is stored in the cursor offset register, and at least a portion of the received data is stored with the cached cursor information.

Abstract: A method and apparatus is used in a graphics system to scan a polygon that minimizes the number of pixels scanned outside of the polygon. A direction (e.g., the direction of the major scan axis) is chosen so that once inside the polygon, advancements along the direction do not take the scanning outside of the polygon until substantially all of the interior pixels of the polygon have been scanned. The direction is selected based on the angular orientations of the edges of the polygon. During the scanning, advancements along the direction result in starting points from which lines are pixels are scanned (e.g., lines following a minor scan axis). Each line of pixels ends at one of the edges of the polygon.

Abstract: A method and apparatus for determining visibility of determining a pixel during video rendering is accomplished by determining z-positioning information of an object element. The z-positioning information is representative of the z-information of an object element in a particular section of the display. For example, the z-positioning information may be the two most significant bits of the z-parameter, or information, of an object element. Having determined the z positioning information, a comparison is made between the z positioning information of the object element and z positioning information stored in temporary memory. If this is the first object element being rendered, the z positioning information stored in the temporary memory will be initial z positioning information. When the comparison is favorable, i.e.

Abstract: A method and apparatus for controlling an output frequency of a phase locked loop is accomplished by determining a plurality of divider ratios which are based on an input frequency, parameters, and a desired output frequency. Each of the divider ratios is representative of a ratio between the output frequency and input frequency of the phase locked loop. Having determined the plurality of divider ratios, another determination is subsequently made to determine whether the plurality of divider ratios enable the phase locked loop to produce the output frequency within a given frequency tolerance, i.e., within an allowable error. The determination is based on whether changing the divider ratio from the one of the plurality of ratios to an adjacent ratio causes the output frequency to change more than the allowable error. If so, the plurality of ratios needs to be recalculated based on a change in the input frequency and/or one of the parameters.

Abstract: A method and apparatus for processing administration in a secure community, or communication system, is accomplished by dividing the single computing devices functionality of the administrator/officer/server into physically separate computing devices that function as a serving entity and an administrative entity. In the secure system, when an administrative entity has an administrative function to perform for one of its end-users, it requests a permissions matrix from the serving entity. The serving entity, after authenticating the administrative entity, sends the permissions matrix to the requesting administrative entity in an encoded format. The permissions matrix indicates which administrative functions the requesting administrative entity is authorized to perform for its affiliated end-users. Upon receiving the permissions matrix, the administrative entity verifies the authenticity of the permissions matrix based on the encoded format.

Abstract: A method and apparatus for providing serial transmission of a parallel input is accomplished by a parallel input serial output transmitter that includes a shift register operably coupled to receive a parallel input and to provide data serially to a gating circuit. The gating circuit, based on the state of the data it receives, generates a drive signal which causes a switching circuit to route current from a first current source to a second current source over different paths to produce a serial output. A bias circuit is coupled to the switching circuit to bias the serial output to a desired level.

Abstract: A method and apparatus for self-testing of a multimedia subsystem is accomplished by retrieving a pattern from a first section of memory, where the retrieving is done by a video graphics circuit. Having retrieved the pattern, the video graphics circuit provides it to a video capture circuit via a television encoder. Upon receiving the pattern, the video capture board generates a capture pattern therefrom. The capture pattern is then provided by the video capture circuit to memory via the video graphics circuit. Once the video capture pattern is stored in memory, the capture pattern is compared with the original pattern. When the comparison is favorable, the video capture circuit, the television tuner, and the interconnecting paths have passed testing.

Abstract: A method and apparatus that automatically scales the channel display area (i.e., thumbnails of the channels) based on the number of channels and displaying characteristics and that provides the user with options to customize the plurality of channels displayed in the multi-channel display is accomplished by determining whether all of the channels in the user's customized list can be displayed within the given display area, which may be the full screen or a portion thereof. If all of the channels can be displayed in the given display area, another determination is made to determine the size of each of channel display areas (i.e., thumbnail). Having made this determination, visual representations of each channel in the user's customized list is displayed. While the multi-channel display is being presented, the user can select one of them for customized editing.

Abstract: A rasterizer is used with a system capable of furnishing raster data representative of a string of characters to be formed on a display. The rasterizer has an input interface that is connected to receive the raster data from the system. A graphics engine is connected to use the raster data to simultaneously store representations of portions of at least two of the characters in a memory. An output interface is connected to use the representations stored in the memory to form an output signal which is used by the display to form the characters.

Abstract: A method and apparatus for providing interlaced video data on a progressive display is accomplished upon receiving interlaced image data that is temporally and spatially accurate and calculating, based on a first predetermined function, calculated image data. Next, the calculated image data is compared to a threshold. When the calculated image data exceeds the threshold, the received interlaced image data is adjusted to approximate the threshold. When the calculated image data does not exceed the threshold, the received interlaced image data is adjusted to equal the calculated interlaced data. Having done this, additional information is created and subsequently combined with the adjusted interlaced image data to produce a complete field for display on the progressive display. The additional image information is of a first value when the calculated image data does not exceed the threshold and is as functional value when the calculated image data exceeds the threshold.

Abstract: A method and apparatus for generating a finely adjustable clock is accomplished by a ring oscillator, a plurality of counting circuits, and a controller. The ring oscillator generates a plurality of oscillations, wherein each of the oscillations have an approximately equal period and are phase shifted by an approximately equal phase shift. Each of the plurality of oscillations is provided to one of the counting circuits which divides the frequency of the respective oscillation by a given count value to produce corresponding periodic representation. The controller selects one of the corresponding periodic representations based on control signal to be the output oscillation, or clock signal. When the clock signal needs to be finely adjusted, the controller, based on the control signal, selects another one of the corresponding periodic representations.