TV receiver having zoom processing apparatus

Claim 1

A signal processing apparatus comprising: a source of an incoming video signal including recurring horizontal and vertical sync pulses; a source of clock pulses occurring at a rate that is substantially greater than the rate of occurrence of said horizontal sync pulses; means coupled to said incoming video signal source, and responsive to said horizontal and vertical sync pulses, for generating window timing pulses occurring between successive vertical sync pulses; a first clock pulse counting means coupled to said source of clock pulses for generating a horizontal timing pulse HTP everytime the clock pulse count reaches a horizontal count limit HCL; said first counting means further providing a train of one-half horizontal period timing pulses having twice the rate of occurrence as said horizontal timing pulses; a second counting means coupled to said first counting means for counting said one-half horizontal period timing pulses and outputting a vertical timing pulse VTP everytime the one-half horizontal period pulse count reaches a vertical count limit VCL during the occurrence of said window timing pulses; and control means coupled to at least one of said first and second counting means and responsive to said window timing pulses for incrementing and decrementing at least one of said horizontal and vertical count limits HCL and VCL in a manner causing said second counting means to reach said vertical count limit VCL during said occurrence of said window timing pulses.