Method and apparatus for simultaneously displaying graphics and video data on a computer display

Claim 1

A method of simultaneously displaying graphics data and video data on a display screen (54) of a computer system having graphics memory (58, 60) and video memory (46) arranged to store image information to be displayed on the display screen (54), the display screen (54) displaying a multiplicity of pixels, wherein the graphics memory (58, 60) and the video memory (46) are each arranged to transmit a sequence of blocks of pixel data to the display screen (54) on output channels (82), and wherein each block of pixel data includes data for a plurality of screen pixels that is to be transmitted simultaneously as a block, the method comprising the steps of: storing graphics data received from a graphics source (31,34) in the graphics memory (58, 60); storing video data received from a video source (40) in the video memory (46); selectively outputting graphics data for a block of pixels simultaneously from the graphics memory (58, 60) on a number of graphics channels (62) when only graphics data is to be transmitted to the screen on the output channels (82) connected to said graphics channels (62); selectively outputting video data for a block of pixels simultaneously from the video memory (46) on a number of video channels (74) corresponding to said number of graphics channels (62) when only video data is to be transmitted to the screen on said output channels (82), wherein said video channels (74) are coupled to said graphics channels (62) to form said output channels (82) and wherein either graphics data or video data is output to a display screen (54) on each output channel (82); characterised in that, when both graphics data and video data are to be transmitted to the screen simultaneously in a single block of data on said output channels (82), selectively causing the output channels that are intended to carry graphics data to transmit only graphics data and selectively causing the output channels that are intended to carry video data to transmit only video data by reading a window-type memory (38) to determine which pixels on said screen (54) are intended to display graphics data and which pixels on said screen (54) are intended to display video data.

Claim 8

A method as recited in any preceding claim wherein said number of graphics channels (62) and said number of video channels (74) is four.

Claim 9

A method as recited in any preceding claim further comprising a step of receiving an analog video signal from said video source (40), converting said analog video signal into digital video data and storing said digital video data in said video memory (46).

Claim 11

A method as recited in any preceding claim wherein said video data transmitted to said screen is 24-bit true color video data.

Claim 12

An apparatus for simultaneously displaying graphics data and video data on a display screen of a computer system, the apparatus comprising: a graphics memory (58, 60) having a set of output graphics channels (62) suitable for simultaneously transmitting graphics data for a plurality of screen pixels; a video memory (46) having a set of output video channels (74) suitable for simultaneously transmitting video data for a plurality of screen pixels; and a converter element (50) for converting data on said output channels (82) into a form suitable for driving a display screen (54) of a computer system, characterised in that each said video channel (74) is coupled to a corresponding graphics channel (62) to form a pair of channels and in that an output channel (82) is coupled to each of said pairs of graphics channels (62) and video channels (74), there being a selection element (48) for selectively causing either data from said graphics memory (58, 60) or data from said video memory (46) to pass on each of said output channels (82) such that the output channels may transmit a block of pixel data that simultaneously includes both graphics data and video data divided on a discrete pixel-by-pixel basis, wherein said selection element includes window-type memory (38) having a memory map of a location of a video window for display on a display screen (54) of a computer system.

Claim 16

An apparatus as recited in any one of claims 12 to 15 wherein said selection element includes source selection logic (48) operative to read said memory map in said window-type memory (38) and to select said data on said output channels (82) according to said window-type memory.

Claim 18

An apparatus as recited in any one of claims 12 to 17 wherein said converter element (50) includes a digital-to-analog converter (DAC).

Claim 20

An apparatus as recited in any one of claims 12 to 19 wherein said set of graphics channels (62) and said set of video channels (74) each include four channels.

Claim 21

An apparatus as recited in any one of claims 12 to 20 wherein said video memory (46) is operable to store a number of dummy pixels positioned before said video data in said video memory such that said dummy pixels are output on video channels that are not selected to output to said converter element (50).

Claim 22

An apparatus as recited in any one of claims 12 to 21 further comprising a frame grabber controller (52) coupled to said video memory (46) and said selection element (50) for controlling the output of video data from said video memory (46).