Method and apparatus for merging independently generated internal video with external video

Claim 1

A method of mixing independently generated internal video with at least one external video to provide a compound video signal to a display device, where said at least one external video is supplied with an external sync signal and said internal video comprises one of a stored video read out of storage with an internal video sync signal and an internally generated video provided with an internal video sync signal, said method is capable of synchronous and asynchronous operation and comprising the steps of: clicking said at least one external video into at least one dual port external frame storage by means of said external sync signal; clocking said internal video into an internal frame store memory; clocking said at least one external video out of said at least one dual port external frame storage and into a data multiplexer by means of a display sync signal; clocking said internal video out of said internal frame store memory and into said data multiplexer by means of said display sync signal; controlling said data multiplexer so as to choose and pass desired portions of said internal video and said at least one external video forming a compound video signal provided to said display device by means of said display sync signal.

Claim 2

A method of mixing independently generated internal video with at least one external video to provide a compound video signal to a display device, where said at least one external video is supplied with an external sync signal and said internal video comprises one of a stored video read out of storage with an internal video sync signal and an internally generated video provided with an internal video sync signal, said method is capable of synchronous and asynchronous operation and comprising the steps of: clicking said at least one external video into at least one dual port external frame storage by means of said external sync signal; clocking said internal video into an internal frame store memory; clocking said at least one external video out of said at least one dual port external frame storage and into a data multiplexer by means of a display sync signal; clocking said internal video out of said internal frame store memory and into said data multiplexer by means of said display sync signal; controlling said data multiplexer so as to choose and pass desired portions of said internal video and said at least one external video forming a compound video signal provided to said display device by means of said display sync signal.

Claim 7

A method of processing a digital video signal to provide a "pan" and "zoom" capability for video signals supplied to an LCD display device, where said digital video is supplied with a video sync signal, said method comprising the steps of: clocking said digital video into a dual port frame storage by means of said video sync signal at predetermined row and column address locations, where said predetermined row and column address locations are related to rows and columns of said display device; and clocking said video out of said frame storage and into said display by means of a display sync signal, said display sync signal asynchronous with respect to said video sync signal, and a row and column counter, where said row and column counter is controlled by a controller which establishes a beginning row and column address dependent upon the portion of the digital video to which the display device is to be "panned" and which repeats each address a predetermined number of times for a respective row and column, until the end of a respective row and column of the display device is reached, said predetermined number of times dependent upon the amount of "zoom" desired.

Claim 8

A method of processing a digital video signal to provide a "pan" and "zoom" capability for video signals supplied to an LCD display device, where said digital video is supplied with a video sync signal, said method comprising the steps of: clocking said digital video into a dual port frame storage by means of said video sync signal at predetermined row and column address locations, where said predetermined row and column address locations are related to rows and columns of said display device; and clocking said video out of said frame storage and into said display by means of a display sync signal, said display sync signal asynchronous with respect to said video sync signal, and a row and column counter, where said row and column counter is controlled by a controller which establishes a beginning row and column address dependent upon the portion of the digital video to which the display device is to be "panned" and which repeats each address a predetermined number of times for a respective row and column, until the end of a respective row and column of the display device is reached, said predetermined number of times dependent upon the amount of "zoom" desired.

Claim 9

A method of processing a digital video signal to provide a reverse or "mirror" image capability for video signals supplied to a display device, where said digital video is supplied with a video sync signal, said method comprising the steps of: clocking complete lines of said digital video into a dual port frame storage by means of said video sync signal at row address locations related to rows of said display device and at column address locations related to one of (a) a reverse of address locations related to column locations of said display device and (b) column locations of said display device; setting a beginning row and column address in an output row and column counter means, where a beginning row address is related to a beginning row on said display device and a beginning column address is related to the other of said (a) reverse of locations related to column locations on said display device and (b) column locations on said display device; and clocking complete lines of said stored digital video out of said dual port frame storage and into said display device.

Claim 10

A method of processing a digital video signal to provide a reverse or "mirror" image capability for video signals supplied to a display device, where said digital video is supplied with a video sync signal, said method comprising the steps of: clocking complete lines of said digital video into a dual port frame storage by means of said video sync signal at row address locations related to rows of said display device and at column address locations related to one of (a) a reverse of address locations related to column locations of said display device and (b) column locations of said display device; setting a beginning row and column address in an output row and column counter means, where a beginning row address is related to a beginning row on said display device and a beginning column address is related to the other of said (a) reverse of locations related to column locations on said display device and (b) column locations on said display device; and clocking complete lines of said stored digital video out of said dual port frame storage and into said display device.

Claim 12

A method of mixing independently generated internal digital video with external digital video to provide a compound video signal to a display device, including providing a "pan", "zoom" and reverse or "mirror" image capability for digital video signals supplied to a display device, where said external digital video is supplied with an external sync signal and said internal digital video comprises one of a stored video read out of storage with an internal video sync signal and an internally generated video provided with an internal video sync signal, said method comprising the steps of: clocking, by means of said external sync signal, said external digital video into a dual port external frame storage at predetermined row and column address locations where said predetermined row and column address locations are related to rows and columns of said display device, said row address locations related to rows of said display device and said column address locations are related to one of a reverse of address locations related to column locations of said display device and (b) column locations of said display device; clocking said internal digital video into an internal frame store memory; determining whether a reverse image is required and, if so, setting a beginning row and column address in an output row ana column counter means, where a beginning row address is related to a beginning row on said display device and a beginning column address is related to the other of said (a) reverse of locations related to column locations of said display device and (b) column locations on said display device; clocking said stored external video out of said external frame storage and into a data multiplexer by means of a display sync signal and a row and column counter, where said row and column counter is controlled by a controller which establishes a beginning row and column address in said display sync row and column counter dependent upon the portion of digital video to which the display device is to be "panned" and which repeats each address a predetermined number of times for each row and column, until the end of a respective row and column of the display device is reached, said predetermined number of times dependent upon the amount of "zoom" desired; clocking said stored internal video out of said internal frame store memory and into said data multiplexer by means of said display sync signal; and controlling said data multiplexer so as to choose and pass desired portions of said stored internal video and said stored external video forming a compound video signal provided to said display device by means of said display sync signal.

Claim 13

A method of mixing independently generated internal digital video with external digital video to provide a compound video signal to a display device, including providing a "pan", "zoom" and reverse or "mirror" image capability for digital video signals supplied to a display device, where said external digital video is supplied with an external sync signal and said internal digital video comprises one of a stored video read out of storage with an internal video sync signal and an internally generated video provided with an internal video sync signal, said method comprising the steps of: clocking, by means of said external sync signal, said external digital video into a dual port external frame storage at predetermined row and column address locations where said predetermined row and column address locations are related to rows and columns of said display device, said row address locations related to rows of said display device and said column address locations are related to one of a reverse of address locations related to column locations of said display device and (b) column locations of said display device; clocking said internal digital video into an internal frame store memory; determining whether a reverse image is required and, if so, setting a beginning row and column address in an output row ana column counter means, where a beginning row address is related to a beginning row on said display device and a beginning column address is related to the other of said (a) reverse of locations related to column locations of said display device and (b) column locations on said display device; clocking said stored external video out of said external frame storage and into a data multiplexer by means of a display sync signal and a row and column counter, where said row and column counter is controlled by a controller which establishes a beginning row and column address in said display sync row and column counter dependent upon the portion of digital video to which the display device is to be "panned" and which repeats each address a predetermined number of times for each row and column, until the end of a respective row and column of the display device is reached, said predetermined number of times dependent upon the amount of "zoom" desired; clocking said stored internal video out of said internal frame store memory and into said data multiplexer by means of said display sync signal; and controlling said data multiplexer so as to choose and pass desired portions of said stored internal video and said stored external video forming a compound video signal provided to said display device by means of said display sync signal.

Claim 14

An apparatus for mixing independently generated internal video with at least one external video to provide a compound video signal to a display device, where said at least one external video includes at least one external sync signal and said internal video comprises one of a stored video read out of storage with an internal video sync signal and an internally generated video provided with an internal video sync signal, said apparatus comprising: at least one dual port external frame store memory; external sync signal means for clocking said at least one external video into said at least one dual port external frame store memory; internal frame store memory; means for clocking said internal video into said internal frame store memory; data multiplexer; display sync signal means for stored external video out of said at least one dual port external frame store memory and for stored internal video out of said internal frame store memory and into said data multiplexer by means of a display sync signal, said data multiplexer comprising means, responsive to said display sync signal, for passing desired portions of said stored internal video and said stored external video thereby forming a compound video signal output to said display device.

Claim 15

An apparatus for mixing independently generated internal video with at least one external video to provide a compound video signal to a display device, where said at least one external video includes at least one external sync signal and said internal video comprises one of a stored video read out of storage with an internal video sync signal and an internally generated video provided with an internal video sync signal, said apparatus comprising: at least one dual port external frame store memory; external sync signal means for clocking said at least one external video into said at least one dual port external frame store memory; internal frame store memory; means for clocking said internal video into said internal frame store memory; data multiplexer; display sync signal means for stored external video out of said at least one dual port external frame store memory and for stored internal video out of said internal frame store memory and into said data multiplexer by means of a display sync signal, said data multiplexer comprising means, responsive to said display sync signal, for passing desired portions of said stored internal video and said stored external video thereby forming a compound video signal output to said display device.

Claim 18

An apparatus for processing a digital video signal to provide a "pan" and "zoom" capability for video signals supplied to an LCD display device, where said digital video is supplied with a video sync signal, said apparatus comprising: a dual port frame store; sync signal means for clocking said digital video into said dual port frame store at row and column address locations, where said row and column address locations are related to rows and columns of said display device; row and column counter means, responsive to a controller means, for clocking said digital video out of said frame store and into said display device; and said controller means comprising a means for generating a display sync signal asynchronous with respect to said video sync signal, said controller means including a means for setting a beginning row and column address for said row and column counter means, said beginning row and column address dependent upon a portion of said digital video to which the display device is to be "panned", said controller means including a means for repeating each row and column address a predetermined number of times until the end of a respective row and column of the display device is reached, said predetermined number of times dependent upon the amount of "zoom" desired.

Claim 19

An apparatus for processing a digital video signal to provide a "pan" and "zoom" capability for video signals supplied to an LCD display device, where said digital video is supplied with a video sync signal, said apparatus comprising: a dual port frame store; sync signal means for clocking said digital video into said dual port frame store at row and column address locations, where said row and column address locations are related to rows and columns of said display device; row and column counter means, responsive to a controller means, for clocking said digital video out of said frame store and into said display device; and said controller means comprising a means for generating a display sync signal asynchronous with respect to said video sync signal, said controller means including a means for setting a beginning row and column address for said row and column counter means, said beginning row and column address dependent upon a portion of said digital video to which the display device is to be "panned", said controller means including a means for repeating each row and column address a predetermined number of times until the end of a respective row and column of the display device is reached, said predetermined number of times dependent upon the amount of "zoom" desired.

Claim 20

An apparatus for processing a digital video signal to provide a reverse or "mirror" image capability for video signal supplied to a display device, where said digital video is supplied with a video sync signal, said apparatus comprising: dual port frame storage means for storing digital video at row and column address locations; input row and column counter means, responsive to said sync signal, for clocking complete lines of said digital video into said dual port frame storage means at row address locations related to rows of said display device and said column address locations related to one of (a) a reverse of locations related to column locations of said display device and (b) column locations of said display device; output row and column counter means, responsive to a display sync signal and a controller means, for clocking complete lines of said digital video out of dual port frame storage means and into said display device; and controller means for setting a beginning row and column address in said output row and column counter means, where a beginning row address is related to a beginning row on said display device and a beginning column address is related to the other of said (a) reverse of locations related to column locations on said display device and (b) column locations on said display device.

Claim 21

An apparatus for processing a digital video signal to provide a reverse or "mirror" image capability for video signal supplied to a display device, where said digital video is supplied with a video sync signal, said apparatus comprising: dual port frame storage means for storing digital video at row and column address locations; input row and column counter means, responsive to said sync signal, for clocking complete lines of said digital video into said dual port frame storage means at row address locations related to rows of said display device and said column address locations related to one of (a) a reverse of locations related to column locations of said display device and (b) column locations of said display device; output row and column counter means, responsive to a display sync signal and a controller means, for clocking complete lines of said digital video out of dual port frame storage means and into said display device; and controller means for setting a beginning row and column address in said output row and column counter means, where a beginning row address is related to a beginning row on said display device and a beginning column address is related to the other of said (a) reverse of locations related to column locations on said display device and (b) column locations on said display device.

Claim 23

An apparatus for mixing independently generated internal digital video with external digital video to provide a compound video signal to a display device and to provide a "pan", "zoom" and a "mirror" or reverse image capability to said compound video signal, where said external digital video includes an external sync signal and said internal digital video comprises one of a stored video read out of storage with an internal video sync signal and an internally generated video provided with an internal video sync signal, said apparatus comprising: a dual port external frame store memory means for storing external digital video at row and column address locations; input row and column counter means, responsive to said external sync signal, for clocking said external digital video into said dual port frame store memory means at row address locations related to rows of said display device and said column address locations related to one of (a) a reverse of locations related to column locations of said display device and (b) column locations of said display device; internal frame store memory; means for clocking said internal digital video into said internal frame store memory; data multiplexer means, responsive to a display sync signal, for passing desired portions of stored internal digital video and stored external digital video thereby forming a compound video signal output to said display device; output row and column counter means, responsive to a display sync signal and a controller means, for clocking said stored external digital video out of said external frame store memory means and into said data multiplexer means; and controller means for clocking said stored internal digital video out of said internal frame store memory and into said data multiplexer means by means of a display sync signal, said controller means including means for generating said display sync signal, said controller means including a means for setting a beginning row and column address for said output row and column counter means, said beginning row and column address dependent upon a portion of digital video to which the display device is to be "panned", said controller means including a means for repeating each row and column address a predetermined number of times until the end of a respective row and column of the display device is reached, said predetermined number of times dependent upon the amount of "zoom" desired, where said beginning row address is related to a beginning row on said display device and said beginning column address is related to the other of said (a) reverse of locations related to column locations on said display device and (b) column locations on said display device.

Claim 24

An apparatus for mixing independently generated internal digital video with external digital video to provide a compound video signal to a display device and to provide a "pan", "zoom" and a "mirror" or reverse image capability to said compound video signal, where said external digital video includes an external sync signal and said internal digital video comprises one of a stored video read out of storage with an internal video sync signal and an internally generated video provided with an internal video sync signal, said apparatus comprising: a dual port external frame store memory means for storing external digital video at row and column address locations; input row and column counter means, responsive to said external sync signal, for clocking said external digital video into said dual port frame store memory means at row address locations related to rows of said display device and said column address locations related to one of (a) a reverse of locations related to column locations of said display device and (b) column locations of said display device; internal frame store memory; means for clocking said internal digital video into said internal frame store memory; data multiplexer means, responsive to a display sync signal, for passing desired portions of stored internal digital video and stored external digital video thereby forming a compound video signal output to said display device; output row and column counter means, responsive to a display sync signal and a controller means, for clocking said stored external digital video out of said external frame store memory means and into said data multiplexer means; and controller means for clocking said stored internal digital video out of said internal frame store memory and into said data multiplexer means by means of a display sync signal, said controller means including means for generating said display sync signal, said controller means including a means for setting a beginning row and column address for said output row and column counter means, said beginning row and column address dependent upon a portion of digital video to which the display device is to be "panned", said controller means including a means for repeating each row and column address a predetermined number of times until the end of a respective row and column of the display device is reached, said predetermined number of times dependent upon the amount of "zoom" desired, where said beginning row address is related to a beginning row on said display device and said beginning column address is related to the other of said (a) reverse of locations related to column locations on said display device and (b) column locations on said display device.

Claim 25

An apparatus for mixing independently generated internal digital video with external digital video to provide a compound video signal to a display device and to provide a "pan", "zoom" and a "mirror" or reverse image capability to said compound video signal, where said external digital video includes an external sync signal and said internal digital video comprises one of a stored video read out of storage with an internal video sync signal and an internally generated video provided with an internal video sync signal, said apparatus comprising: an input row and column counter means, responsive to said external sync signal and a reverse image control signal, for generating row and column address outputs to a dual port external frame store memory means, said row address outputs related to rows of said display device and said column address outputs related to a reverse of locations related to column locations of said display device when said reverse image control signal is present and locations related to column locations of said display device when said reverse image control signal is not present; a dual port external frame store memory means, responsive to said input row and column counter, for storing external digital video at said generated row and column address locations; at least one of an internal digital video generator and an internal digital video mass storage means; microprocessor controller means, responsive to an operator input, (a) for transmitting said reverse image control signal to said input row and column counter means, (b) for transmitting a "zoom" control output indicative of a desired amount of "zoom", (c) for accessing at least one of said internal digital video generator and internal digital video mass storage means and for providing an internal digital video output, said internal digital video output including an external/internal selection code, and (d) for setting a beginning row and column address for an output row and column counter means by means of a "pan" control signal, said beginning row and column address dependent upon a portion of said digital video to which the display device is to be "panned"; internal frame store memory means for storing digital internal video at row and column address locations related to rows and columns of said display device; graphics chip controller means, responsive to said microprocessor controller means internal video output, (a) for supplying said internal video output to row and column address locations in said internal frame store memory means, (b) for reading out stored internal digital video from said internal frame storage means, and (c) for providing a display sync signal; decoder means, responsive to said internal video output from said graphics chip controller means, for providing an external/internal digital video select signal; data multiplexer means, responsive to (a) a display sync signal, (b) said external/internal digital video select signal, (c) said internal digital video from said graphics chip controller means, (d) said external digital video from said external frame store, for passing selected portions of said internal digital video and said external digital video to said display and said external video to said display device thereby forming a compound digital video signal output; output row and column counter means, responsive to said display sync signal, a slowed sync signal, said "pan" control signal, and said "zoom" control signal, for setting row and column addresses for clocking said digital video out of said external clocking said digital video out of said external frame storage means and into said data multiplexer, where a beginning output row and column address is related to a beginning row and column address on said display device; output data clock control means, responsive to said display sync signal and said "zoom" control signal, for providing a slowed sync signal to said output row and column counter means and to said external frame store memory means, said slowed sync signal slowed 1/x where x is an integer corresponding to a desired amount of "zoom", said output row and column counter means including means for advancing the count of row and column addresses by said slowed sync signal while reading out external digital video data from row and column address locations in said external frame store memory means synchronized with said display sync signal, until the end of a respective row and column of the display device is reached.

Claim 26

An apparatus for mixing independently generated internal digital video with external digital video to provide a compound video signal to a display device and to provide a "pan", "zoom" and a "mirror" or reverse image capability to said compound video signal, where said external digital video includes an external sync signal and said internal digital video comprises one of a stored video read out of storage with an internal video sync signal and an internally generated video provided with an internal video sync signal, said apparatus comprising: an input row and column counter means, responsive to said external sync signal and a reverse image control signal, for generating row and column address outputs to a dual port external frame store memory means, said row address outputs related to rows of said display device and said column address outputs related to a reverse of locations related to column locations of said display device when said reverse image control signal is present and locations related to column locations of said display device when said reverse image control signal is not present; a dual port external frame store memory means, responsive to said input row and column counter, for storing external digital video at said generated row and column address locations; at least one of an internal digital video generator and an internal digital video mass storage means; microprocessor controller means, responsive to an operator input, (a) for transmitting said reverse image control signal to said input row and column counter means, (b) for transmitting a "zoom" control output indicative of a desired amount of "zoom", (c) for accessing at least one of said internal digital video generator and internal digital video mass storage means and for providing an internal digital video output, said internal digital video output including an external/internal selection code, and (d) for setting a beginning row and column address for an output row and column counter means by means of a "pan" control signal, said beginning row and column address dependent upon a portion of said digital video to which the display device is to be "panned"; internal frame store memory means for storing digital internal video at row and column address locations related to rows and columns of said display device; graphics chip controller means, responsive to said microprocessor controller means internal video output, (a) for supplying said internal video output to row and column address locations in said internal frame store memory means, (b) for reading out stored internal digital video from said internal frame storage means, and (c) for providing a display sync signal; decoder means, responsive to said internal video output from said graphics chip controller means, for providing an external/internal digital video select signal; data multiplexer means, responsive to (a) a display sync signal, (b) said external/internal digital video select signal, (c) said internal digital video from said graphics chip controller means, (d) said external digital video from said external frame store, for passing selected portions of said internal digital video and said external digital video to said display and said external video to said display device thereby forming a compound digital video signal output; output row and column counter means, responsive to said display sync signal, a slowed sync signal, said "pan" control signal, and said "zoom" control signal, for setting row and column addresses for clocking said digital video out of said external clocking said digital video out of said external frame storage means and into said data multiplexer, where a beginning output row and column address is related to a beginning row and column address on said display device; output data clock control means, responsive to said display sync signal and said "zoom" control signal, for providing a slowed sync signal to said output row and column counter means and to said external frame store memory means, said slowed sync signal slowed 1/x where x is an integer corresponding to a desired amount of "zoom", said output row and column counter means including means for advancing the count of row and column addresses by said slowed sync signal while reading out external digital video data from row and column address locations in said external frame store memory means synchronized with said display sync signal, until the end of a respective row and column of the display device is reached.

Claim 27

A method of mixing independently generated internal video with at least one external video to provide a compound video signal to a display device, where said at least one external video is supplied with at least one external sync signal and said internal video comprises one of a stored video read out of storage with an internal video sync signal and an internally generated video provided with an internal video sync signal, said method is capable of synchronous and asynchronous operation and comprising the steps of: clocking said at least one external video into at least one dual port external frame storage by means of said external sync signal; clocking said internal video into an internal frame store memory, said internal video clocking step including the step of embedding an at least one external/internal selection code in said internal video; clocking said at least one stored external video out of said at least one dual port external frame storage and into a data multiplexer by means of a display sync signal; clocking said stored internal video out of said internal frame store memory and into said data multiplexer by means of said display sync signal; coding said stored internal video clocked out of said internal frame store memory to determine from the at least one external/internal selection code whether one of said at least one stored external video and stored internal video is to be displayed; and controlling said data multiplexer in response to said decoded at least one external/internal selection code so as to choose and pass desired portions of said at least one stored external video and said stored internal video forming a compound video signal provided to said display device by means of said display sync signal.

Claim 28

A method of mixing independently generated internal video with at least one external video to provide a compound video signal to a display device, where said at least one external video is supplied with at least one external sync signal and said internal video comprises one of a stored video read out of storage with an internal video sync signal and an internally generated video provided with an internal video sync signal, said method is capable of synchronous and asynchronous operation and comprising the steps of: clocking said at least one external video into at least one dual port external frame storage by means of said external sync signal; clocking said internal video into an internal frame store memory, said internal video clocking step including the step of embedding an at least one external/internal selection code in said internal video; clocking said at least one stored external video out of said at least one dual port external frame storage and into a data multiplexer by means of a display sync signal; clocking said stored internal video out of said internal frame store memory and into said data multiplexer by means of said display sync signal; coding said stored internal video clocked out of said internal frame store memory to determine from the at least one external/internal selection code whether one of said at least one stored external video and stored internal video is to be displayed; and controlling said data multiplexer in response to said decoded at least one external/internal selection code so as to choose and pass desired portions of said at least one stored external video and said stored internal video forming a compound video signal provided to said display device by means of said display sync signal.

Claim 30

An apparatus for mixing independently generated internal video with at least one external video to provide a compound video signal to a display device, where said at least one external video includes at least one external sync signal and said internal video comprises one of a stored video read out of storage with an internal vide sync signal and an internally generated video provided with an internal video sync signal, said apparatus comprising: at least one dual port external frame store memory; external sync signal means for clocking said at least one external video into said at least one dual port external frame store memory; internal frame store memory; means for clocking said internal video into said internal frame store memory, said internal video clocking means including means for embedding an at least one external/internal selection code in said internal video; data multiplexer; decoder means, responsive to said embedded at least one external/internal selection code, for providing an at least one external/internal select signal to said data multiplexer; and display sync signal means for clocking external video out of said at least one dual port external frame store memory and for clocking internal video out of said internal frame store memory and into said data multiplexer by means of a display sync signal, said data multiplexer comprising means, responsive to said display sync signal and said at least one external/internal select signal, for passing desired portions of selected external video and said internal video thereby forming a compound video signal output to said display device.

Claim 31

An apparatus for mixing independently generated internal video with at least one external video to provide a compound video signal to a display device, where said at least one external video includes at least one external sync signal and said internal video comprises one of a stored video read out of storage with an internal vide sync signal and an internally generated video provided with an internal video sync signal, said apparatus comprising: at least one dual port external frame store memory; external sync signal means for clocking said at least one external video into said at least one dual port external frame store memory; internal frame store memory; means for clocking said internal video into said internal frame store memory, said internal video clocking means including means for embedding an at least one external/internal selection code in said internal video; data multiplexer; decoder means, responsive to said embedded at least one external/internal selection code, for providing an at least one external/internal select signal to said data multiplexer; and display sync signal means for clocking external video out of said at least one dual port external frame store memory and for clocking internal video out of said internal frame store memory and into said data multiplexer by means of a display sync signal, said data multiplexer comprising means, responsive to said display sync signal and said at least one external/internal select signal, for passing desired portions of selected external video and said internal video thereby forming a compound video signal output to said display device.