Chromakey signal producing apparatus

Claim 2

A chromakey signal producing apparatus, comprising: means for extracting Y, I and Q components from an input composite video signal; means for computing a first difference signal by computing a first difference between at least one of said Y, I and Q components extracted by said extracting means and a corresponding one of Y, I and Q components of a first reference signal; and for computing a second difference between said one of Y, I and Q components of said first reference signal and a corresponding one of Y, I, and Q components of a second reference signal; and means for producing a chromakey signal by controlling the level of said first difference signal in accordance with said second difference.

Claim 3

The chromakey signal producing apparatus as claimed in claim 1, in which said first reference signal respresents a color to be keyed and said second reference signal represents a color not to be keyed.

Claim 4

The chromakey signal producing apparatus as claimed in claim 1, in which said chromakey signal producing means includes: means for computing the quotient value of said first difference divided by said second difference; and means for clipping said quotient value according to a predetermined clipping value to produce said chromakey signal.

Claim 5

A chromakey signal producing apparatus as claimed in claim 1, further comprising: means for producing said first reference signal and said second reference signal by holding at least one of said Y, I and Q components extracted from said input composite video signal at the occurrences of a first timing and a second timing, respectively; and means for controlling said first and second timing, respectively.

Claim 6

A chromakey signal producing apparatus, comprising: (a) means for separating Y, I and Q component signals from an input composite video signal; and (b) means for (1) designating a first reference color corresponding to a color to be keyed, said first reference color being indicated by a set of first reference components Y 0 , and I 0 and Q 0 ; (2) designating a second reference color corresponding to a color not to be keyed, said second reference color being indicated by a set of second reference components Y 1 , I 1 and Q 1 ; (3) computing a first difference between at least one of said Y, I and Q component signals separated by said separating means and a corresponding one of said first reference components Y 0 , I 0 and Q 0 to generate a primary key signal; (4) computing a second difference between at least one of said first reference components Y 0 , I 0 and Q 0 and a corresponding one of said second reference components Y 1 , I 1 and Q 1 to generate a compensation level; and (5) producing a chromakey signal by controlling the level of said primary key signal in accordance with said compensation level.

Claim 7

A chromakey signal producing apparatus, comprising: (a) means for separating Y, I and Q component signals from an input composite video signal; and (b) means for (1) designating a first reference color corresponding to a color to be keyed, said first reference color being indicated by a set of first reference components Y 0 , and I 0 and Q 0 ; (2) designating a second reference color corresponding to a color not to be keyed, said second reference color being indicated by a set of second reference components Y 1 , I 1 and Q 1 ; (3) computing a first difference between at least one of said Y, I and Q component signals separated by said separating means and a corresponding one of said first reference components Y 0 , I 0 and Q 0 to generate a primary key signal; (4) computing a second difference between at least one of said first reference components Y 0 , I 0 and Q 0 and a corresponding one of said second reference components Y 1 , I 1 and Q 1 to generate a compensation level; and (5) producing a chromakey signal by controlling the level of said primary key signal in accordance with said compensation level.

Claim 8

A chromakey signal producing apparatus, comprising: (a) means for separating Y, I and Q component signals from an input composite video signal; (b) means for generating first and second timing signals corresponding to respective positions on a TV picture screen; (c) means for (1) extracting components Y 0 , I 0 and Q 0 from said Y, I and Q component signals, respectively, at the time of said first timing signal, the set of said components Y 0 , I 0 and Q 0 corresponding to a first reference color which is to be keyed; (2) extracting components Y 1 , I 1 and Q 1 from said Y, I and Q component signals, respectively, at the time of said second timing signal, the set of said components Y 1 , I 1 and Q 1 corresponding to a second reference color which is not to be keyed; (3) computing first differences (Y-Y 0 ), (I-I 0 ) and (Q-Q 0 ) between said Y, I and Q component signals and said components Y 0 , I 0 and Q 0 , respectively; (4) computing second differences (Y 1 -Y 0 ), (I 1 -I 0 ) and (Q 1 -Q 0 ) between said components Y 1 , I 1 and Q 1 and said components Y 0 , I 0 and Q 0 , respectively; (5) controlling the levels of said first differences (Y-Y 0 ), (I-I 0 ) and (Q-Q 0 ) in accordance with said second differences (Y 1 -Y 0 ), (I 1 -I 0 ) and (Q 1 -Q 0 ), respectively, to deliver levels ##EQU2## wherein α, β and γ are predetermined constants; and (6) adding said levels ##EQU3## to deliver an added level signal; and (d) means for clipping said added level signal by a predetermined clip level to deliver a chromakey signal.

Claim 9

A chromakey signal producing apparatus, comprising: (a) means for separating Y, I and Q component signals from an input composite video signal; (b) means for generating first and second timing signals corresponding to respective positions on a TV picture screen; (c) means for (1) extracting components Y 0 , I 0 and Q 0 from said Y, I and Q component signals, respectively, at the time of said first timing signal, the set of said components Y 0 , I 0 and Q 0 corresponding to a first reference color which is to be keyed; (2) extracting components Y 1 , I 1 and Q 1 from said Y, I and Q component signals, respectively, at the time of said second timing signal, the set of said components Y 1 , I 1 and Q 1 corresponding to a second reference color which is not to be keyed; (3) computing first differences (Y-Y 0 ), (I-I 0 ) and (Q-Q 0 ) between said Y, I and Q component signals and said components Y 0 , I 0 and Q 0 , respectively; (4) computing second differences (Y 1 -Y 0 ), (I 1 -I 0 ) and (Q 1 -Q 0 ) between said components Y 1 , I 1 and Q 1 and said components Y 0 , I 0 and Q 0 , respectively; (5) controlling the levels of said first differences (Y-Y 0 ), (I-I 0 ) and (Q-Q 0 ) in accordance with said second differences (Y 1 -Y 0 ), (I 1 -I 0 ) and (Q 1 -Q 0 ), respectively, to deliver levels ##EQU2## wherein α, β and γ are predetermined constants; and (6) adding said levels ##EQU3## to deliver an added level signal; and (d) means for clipping said added level signal by a predetermined clip level to deliver a chromakey signal.