Graphics subsystem bypass method and apparatus
AssigneeGeneral Instrument Corporation
InventorsDavid E. Zeidler, Robert M. Simons, Joseph A. Petry
Life of this patent
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Abstract
The present invention provides an on-screen graphics (OSD) subsystem for overlaying OSD graphic images onto analog or digital video source signals. The OSD system has a video graphics bypass path and graphics bypass switch for directing an analog video channel around the OSD subsystem during time intervals when the OSD subsystem is not required to insert graphics into the source signal.
Claims22
A cable television video terminal for selectively combining graphics with video signals, the video terminal comprising:
- (a) a tuner for outputting a video signal;
- (b) a digital channel demodulator configured to output a first digital signal in response to receiving the video signal from the tuner;
- (c) an analog channel demodulator configured to output a first analog signal in response to receiving the video signal from the tuner;
- (d) a video output;
- (e) a processor;
- (f) a video graphics subsystem comprising:
- (i) an analog to digital converter configured to output a second digital signal in response to receiving the first analog signal from the analog channel demodulator;
- (ii) an on-screen display (OSD) insertion unit configured to output a composite digital signal generated by combining OSD graphics with a selected one of the first and second digital signals;
- (iii) a first switch, controlled by the processor, for feeding the first digital signal to the OSD insertion unit during selected time intervals when the tuner is tuned to a digital channel, and for feeding the second digital signal to the OSD insertion unit during selected time intervals when the tuner is tuned to an analog channel;
- and
- (iv) a digital to analog converter coupled to the OSD insertion unit and configured to output a second analog signal in response to receiving the composite digital signal;
- and
- (g) a second switch, controlled by the processor, for selectively coupling the video output to the digital to analog converter when the processor determines that OSD graphics are available to be combined with one of the first and second digital signals, and for selectively coupling the video output to the analog to digital converter when the processor determines that there are no OSD graphics available to be combined with the second digital signal.
In a cable television video terminal which includes at least one switch controlled by a processor, a method of selectively combining graphics with video signals, the method comprising:
- (a) outputting a first digital signal when the video terminal is tuned to a digital channel;
- (b) outputting a first analog signal when the video terminal is tuned to an analog channel;
- (c) converting the first analog signal into a second digital signal;
- (d) when the processor determines that graphics are available to be combined with the second digital signal:
- (i) the processor controlling the at least one switch such that the video terminal outputs a composite digital signal generated by combining the graphics with the second digital signal;
- (ii) converting the composite digital signal into a second analog signal;
- and
- (iii) outputting the second analog signal from the video terminal;
- and
- (e) when the processor determines that graphics are not available to be combined with the second digital signal, the processor controlling the at least one switch such that the first analog signal is output from the video terminal.
A cable television video terminal for selectively combining graphics with video signals, the video terminal comprising:
- (a) a first demodulator for outputting a first digital video signal when the video terminal is tuned to a digital channel;
- (b) a second demodulator for outputting a first analog video signal when the video terminal is tuned to an analog channel;
- (c) a first converter for converting the first analog video signal into a second digital video signal;
- (d) a graphics inserter for combining graphics with digital signals inputted into the graphics inserter and outputting a composite signal;
- (e) a first switch for selectively routing the first digital video signal and the second digital video signal to the graphics inserter;
- (f) a second converter for converting the composite signal into a second analog video signal;
- (g) a second switch for selectively outputting one of the first and second analog video signals from the video terminal;
- and
- (h) a processor for controlling the first and second switches, and determining when graphics are available to be combined with the second digital video signal by the graphics inserter.
Dependencies are inferred from the claim text.