Control circuit for mixing two video signals

A method of generating an output signal composed of one or more of a plurality of input signals comprising the steps of:

• a. receiving a plurality of control signals specifying a selected one of a plurality of states including a plurality of separate states, each for including only a corresponding one of the plurality of input signals separately as the output signal and a mixing state for combining the plurality of input signals in a predetermined ratio into the output signal;
• b. generating a plurality of content control signals, each corresponding to an appropriate one of the plurality of input signals and each representing a percentage of the output signal which is to include the appropriate one of the input signals;
• and
• c. receiving a first signal which when active represents a first period during a selected one of the input signals, wherein during the mixing state when the first signal is active, only a predetermined one of the input signals is included within the output signal.

A method of generating an output signal including one or more of a plurality of input video signals in a predetermined ratio, comprising the steps of:

• a. receiving a plurality of control signals and a horizontal blanking signal which when active represents a horizontal blanking period in a selective one of the input video signals;
• b. generating a plurality of content control signals, each corresponding to an appropriate one of the plurality of input video signals and representing a percentage of the output signal which is to include the appropriate one of the input video signals, wherein the output signal will include a selective one of the input video signals or a mixture in the predetermined ratio of the input video signals as specified by the control signals;
• and
• c. providing the content control signals to a mixer circuit for generating the output signal;
• wherein when the control signals specify that the output signal is to include a mixture of the input video signals and the horizontal blanking signal is active, the output signal will include only one of the input video signals.

A video mixer control circuit for generating a first content control signal corresponding to a first composite video signal and a second content control signal corresponding to a second composite video signal, the first and second content control signals representing a percentage of an output signal which is to include the respective corresponding composite video signal, the video mixer control circuit comprising:

• a. a control logic circuit configured to receive a horizontal blanking signal which is active during a horizontal blanking period of the first composite video signal and first and second content control signals, together specifying one of a plurality of states including a first state wherein the output signal includes the first composite video signal only, a second state wherein the output signal includes the second composite video signal only and a third state wherein the output signal includes a mixture in a predetermined ratio of both the first and second composite video signals;
• b. a switching network coupled to and controlled by the control logic circuit for switching between the plurality of states;
• and
• c. an output circuit coupled to and controlled by the switching network for generating the first and second content control signals according to the specified state, wherein when the third state is specified and the horizontal blanking signal is active only the first composite video signal is included within the output signal.

A video display system for receiving video input signals and generating an output video signal comprising:

• a. a first input video receiving circuit configured for receiving a first input signal and a first ground reference signal and generating a first differential signal representative of a difference between the first input signal and the first ground reference signal;
• b. a second input video receiving circuit configured for receiving a second input signal and a second ground reference signal and generating a second differential signal representative of a difference between the second input signal and the second ground reference signal;
• c. a mixer control circuit for generating a first content signal representative of a first percentage of the output video signal which is to include the first differential signal and a second content signal representative of a second percentage of the output video signal which is to include the second differential signal;
• and
• d. a mixing circuit coupled to receive the first and second content signals and the first and second differential signals for combining the first and second differential signals in a predetermined ratio and generating the output video signal.