Apple Inc.

The Grass Valley Group, Inc.

Tektronix, Inc.

James A Delwiche

Giovanni M Agnoli

Andrew Yanowitz

John O Abt

Samuel R Bowman

Jeffrey C Dillon

John Abt

Brion L Dunbar

Neil R Olmstead

David Casper

Scott Murray

James E Blecksmith

Thomas H Knight

A method for controlling data transmission between a computer and a video client via an interface, the method comprising: the computer polling the interface a first time to determine the size of the buffer on the interface; receiving a first buffer size value from the interface; sending a plurality of frames of video and audio data to the buffer on the interface such that a delay period exists between the sending of each frame; the computer polling the interface a second time to determine buffer size after the frames are sent to the interface; receiving a second buffer size value from the interface; and modifying the amount of time between the transmission of frames.

Synchronized transmission of audio and video data from a computer to a client via an interface

A method of controlling transmission of data from a computer to a video client via an interface device, comprising: reading a register on the interface device to obtain a value indicating temporal proximity to an occurrence of a vertical blanking interval occurs, the value increased incrementally until a vertical blanking interval occurs, and then being reset; deriving a time value, the time value indicating the occurrence of a vertical blanking interval; sending an interrupt to a processor on the computer at the occurrence of the vertical blanking interval; and invoking code in response to an occurrence of the video blanking interval.

Synthesis of vertical blanking signal

To provide an improved non-additive mixer, a first mixer mixes first and second video signals according to a mixer control signal derived in a new way. The first and second video signals are applied, respectively, to first and second chrominance (blocking) filters. The resulting first and second luminance signals are applied, respectively, to first and second summing circuits, where offsets may be applied to either or both of them. The difference is then taken between the first offset luminance signal and the second offset luminance signal to produce a difference luminance signal. The difference luminance signal is then multiplied by a gain control signal to produce the mixer control signal. The mixer control signal can also be used to control a second mixer, thereby providing a channel for keying information that is non-additively mixed according to the luminance content of the video signal that the key information is associated with.

Non-additive video mixer

A dynamically paged non-volatile random access video store has a random access memory integrated with a disk drive. The random access memory provides realtime access for recording and playing back video from and to a video source. The disk drive provides a non-volatile backup for the random access memory by transferring data between the disk drive and random access memory automatically, or by command, on a non-realtime basis. The video data accesses and transfers are handled by a microprocessor that interfaces with a controller by which an operator inputs instructions. Multiple channels are accommodated via a channel interface, also controlled by the microprocessor, between external video devices and the random access memory. The disk drive stores a plurality of pages of video data, each page corresponding to the capacity of the random access memory.

Dynamically paged non-volatile random access video store

An improved chroma keyer has a secondary hue selector for chrominance suppression of 'blue fringing' effects. The second hue selector provides a second chroma key signal from a foreground video signal, with the selected hue being offset from that of a primary hue selector. A matte generator having a hue corresponding to the hue of a backing in the foreground video signal is modulated as a function of the second chroma signal. The modulated hue from the matte generator is subtracted from the foreground video signal to produce a modified foreground video signal. The modified foreground video signal is converted into a shaped foreground video signal. The shaped foreground video signal is combined with a shaped background video signal to produce a composited output video signal. The shaped background video signal is a function of a background video signal and a primary chroma key signal from the primary hue selector.

Chroma keyer with secondary hue selector

A pseudo-random pattern generator has modifiable feedback so that a variety of pseudo-random video patterns can be generated and used either directly, or after further manipulation, to control the mixing of two video sources. Control of a multiplexer allows a variety of pattern lengths to be selected by altering which stages of a shift register are supplied to a feedback exclusive-OR gate. Patterns with controllable granularity can be achieved by stretching each part of the noise pattern a selectable number of times along either or both axes. Horizontal stretching is achieved by clocking the shift register more slowly than the rate at which it is being read out. Vertical stretching is achieved by repeating the same pattern on each of a selectable number of consecutive lines. Varying the ratio of the stretching along the horizontal axis to the stretching along the vertical axis allows the aspect ratio of the grains of the pattern to be controlled. The values that are used to initialize the shift register can also be altered to achieve additional variation in the patterns generated. Two (or more) modifiable pseudo-random pattern generators can be used in combination with an array of selectable filters to provide a controllable noise pattern generator with coarse and fine pattern controls and selectable filtering of the output patterns produced.

Controllable pseudo random noise pattern generator for use in video

An adaptive rounder for avoiding truncation errors for digital video signal has a dither source that is modified by the bits of an integer portion of an input digital signal corresponding to the video signal. A dither signal from the dither source has a number of bits equal to a fractional portion of the input digital signal. The dither signal is added to the input digital signal and the result is truncated to produce an output digital signal having a number of bits equal to the integer portion.

Growing community of inventors

Grass Valley, CA, United States of America

James A Delwiche