A method for effecting identification of received format of a video signal at an input locus including a first input pin and a second input pin;
- said received format being one of a first format, a second format or a third format;
- said first format being a broadcast video signal format including a color-related signal received at said second input pin and a synchronizing color-related signal received at said first input pin and having a bi-level raster timing signal occupying a raster synch interval and a respective synch-follower signal level after said raster synch interval;
- said second format being a first color difference component video signal including a first color-difference signal received at said second input pin, and a first luminance-related signal received at said first input pin and having a bi-level raster timing signal occupying said raster synch interval and a respective synch-follower signal level after said raster synch interval;
- said third format being a second color difference component video signal including a second color-difference signal received at said second input pin, and a second luminance-related signal received at said first input pin and having a tri-level raster timing signal occupying said raster synch interval and a respective synch-follower signal level after said raster synch interval;
- the method comprising the steps of:
- (a) clamping the received signals to a reference level at each of said first input pin and said second input pin;
- (b) measuring said received signal at said second input pin during a sample period occupying at least a portion of said raster synch interval to obtain a synch interval measured value for said signal received at said second input pin;
- (c) if said synch interval measured value is greater than a first predetermined value for said signal received at said second input pin, setting a first factor at one, and otherwise setting said first factor at zero;
- (d) accumulating samples of said signal received at said first input pin over said sample period to obtain an accumulated signal synch value for said signal received at said first input pin during said sample period;
- (e) multiplying said respective synch-follower signal level of said signal received at said first pin times the number of samples accumulated in step (d) to obtain a synch-follower sample level;
- (f) subtracting said synch-follower sample level from said accumulated signal synch value to obtain an accumulated sample difference value;
- (g) if said accumulated difference value is less than a second predetermined value, setting a second factor at one, and otherwise setting said second factor at zero;
- (h) measuring peak amplitude of received signal at said second input pin to obtain a peak value for said signal received at said second input pin;
- (i) subtract said synch interval measured value for said signal received at said second input pin from said peak value for said signal received at said second input pin to obtain a peak difference value for said signal received at said second input pin;
- (j) if said peak difference value is greater than a third predetermined value for said signal received at said second input pin, setting a third factor at zero, and otherwise setting said third factor at one;
- (k) employing said first factor, said second factor and said third factor to effect said identification of received format according to predetermined relationships among said first factor, said second factor and said third factor.