Video recorder with a magnetic recording medium in the form of a tape

In a video recorder that includes an analog read/write head which stores analog signals on a recording medium and which reads analog signals from said recording medium, an input terminal that receives an analog composite video input signal, an output terminal that provides a composite video analog output signal, and an electronic circuit operable in a selected one of a record mode and a playback mode and operable in accordance with a selected one of the NTSC, PAL and SECAM television standards, said electronic circuit processing said analog composite video input signal in said record mode and providing an analog representation of said composite video signal to said read/write head to be stored on said recording medium, said electronic circuit processing said analog signals from said read/write head in said playback mode and providing said composite video analog output signal on said output terminal, the improvement wherein said electronic circuit comprises:

• an analog-to-digital convertor that has an input and an output, said analog-to-digital convertor receiving an analog input signal via said input and providing a digital representation of said analog input signal on said output, said analog-to-digital convertor clocked by a first sampling signal having a first fixed frequency that is the same irrespective of the selected one of the television standards, said analog-to-digital convertor providing said digital representation on said output at a rate corresponding to said first fixed frequency of said first sampling signal;
• an input selector switch having a first switch input, a second switch input and a switch output, said first switch input electrically connected to said input terminal, said second switch input electrically connected to said read/write head, and said switch output electrically connected to said input of said analog-to-digital convertor, said input selector switch operable in said record mode to connect said first switch input to said switch output to provide said analog composite video input signal as the analog input signal to said analog-to-digital convertor, said input selector switch operable in said playback mode to connect said second switch input to said switch output to provide said analog signal from said read/write head as the analog input signal to said analog-to-digital convertor, said analog input signal provided to said analog-to-digital convertor including a chrominance component, said digital representation provided by said analog-to-digital convertor comprising a digitized video signal that includes a digital representation of said chrominance component;
• a first digital mixing circuit that has an input and an output, said input of said digital mixing circuit connected to said digitized video signal output of said analog-to-digital convertor, said digital mixing circuit receiving the digitized video signal output of said analog-to-digital convertor at said first fixed frequency and providing a first digital mixing circuit output signal on said mixing circuit output at a second fixed frequency that is a fixed subharmonic of said first fixed frequency, said first digital mixing circuit output signal comprising the chrominance component of said digitized video signal, said first digital mixing circuit comprising a signal generator that generates a first mixing signal that is selected in accordance with the known horizontal frequency of the selected one of the television standards so that said second fixed frequency is the same irrespective of the selected one of the television standards;
• a chrominance processing circuit having an input and an output, said input coupled to receive said first digital mixing circuit output signal from said first digital mixing circuit, said chrominance processing circuit processing said first digital mixing circuit output signal and providing a processed chrominance output signal, said chrominance processing circuit operating at a third fixed frequency that is a fixed subharmonic of said first fixed frequency and that is constant irrespective of the selected one of the television standards;
• a second digital mixing circuit having an input and an output, said input of said second digital mixing circuit coupled to the output of said chrominance processing circuit to receive said processed chrominance output signal, said second digital mixing circuit mixing said processed chrominance output signal with a selected second mixing signal to provide a second digital mixing circuit output signal;
• a first digital-to-analog convertor having an input and an output, said input connected to the output of said second digital mixing circuit to receive said second digital mixing circuit output signal, said digital-to-analog convertor providing an analog output signal corresponding to said second digital mixing circuit output signal;
• a digital composite video circuit having an input and an output, said input connected to said output of said analog-to-digital convertor to receive said digitized video signal, said digital composite video circuit generating a synchronization signal and further generating a digitized luminance signal, said luminance signal provided as an output on said output of said digital composite video circuit;
• a second digital-to-analog convertor having an input and an output, said input connected to said output of said digital composite video circuit to receive said digitized luminance signal, said second digital-to-analog convertor providing an analog representation of said digitized luminance signal on said output of said digital-to-analog convertor;
• an analog adder that has a first input, a second input, and an output, said first input connected to said output of said first digital-to-analog convertor, said second input connected to said output of said second digital-to-analog convertor, said output providing an analog composite video output signal having a chrominance component and a luminance component;
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• a second switch having an input, a first output and a second output, said input connected to said output of said analog adder to receive said analog composite video output signal, said first output connected to said read/write head, said second output connected to said output terminal, said second switch operable to a first condition in said record mode to connect said input to said first output to provide said analog composite video output signal to said read/write head in said record mode and operable to a second condition in said playback mode to connect said input to said output to provide said analog composite video output signal to said output terminal in said playback mode.

In a video recorder that is operable at a selected one of the NTSC, PAL and SECAM television standards, said video recorder having an analog composite video input signal, comprising chrominance, luminance and synchronizing components, said analog composite video input signal switchable between an external video signal source and a video read/write head and having an analog composite video output signal, comprising chrominance, luminance and synchronizing components, said analog composite video output signal switchable between said video read/write head and an external device, an improved electronic circuit that processes said analog composite video input signal and provides said analog composite video output signal, said improved electronic circuit comprising:

• an analog-to-digital convertor having an input and an output, said input receiving said analog composite video input signal, said analog-to-digital convertor sampling said analog composite video input signal at a first fixed sampling rate and providing a digitized composite video output signal at said first fixed sampling rate, said digitized composite video output signal comprising digitized chrominance, luminance and synchronizing components, said first fixed sampling rate constant irrespective of said selected one of said television standards;
• a digital mixer circuit having a first input, a second input and an output, said first input receiving said digitized composite video output signal at said first fixed sampling rate that is the same irrespective of said selected one of said television standards, said second input receiving a mixing signal, said mixing signal having a frequency selected in accordance with said selected one of said television standards, said digital mixer circuit providing an output signal comprising said digitized chrominance component at a second fixed sampling rate that is a predetermined subharmonic of said first fixed sampling rate;
• means coupled to said digital mixer circuit for processing said digitized chrominance component, said means comprising:
• a decimator that samples said digitized chrominance component at a third fixed sampling rate that is a predetermined subharmonic of said first fixed sampling rate and that is the same irrespective of said selected one of said television standards, said decimator providing a decimator output signal;
• a color control circuit coupled to said decimator that operates at said third fixed sampling rate to control the amplitude of said digitized chrominance component and that provides an amplitude-controlled chrominance component;
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• a digital interpolator having an input and an output, said input coupled to said color control circuit, said interpolator operating at said first fixed sampling rate to provide an interpolated output signal corresponding to said processed digitized chrominance component on said output at said first fixed sampling rate;
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• a digital-to-analog convertor having an input and an output, said input coupled to said output of said interpolator to receive said processed digitized chrominance component, said digital-to-analog convertor converting said digitized processed chrominance component to an analog processed chrominance component, said analog processed chrominance component comprising said chrominance component of said analog video composite output signal.