Method of and apparatus for deriving a PAL color television signal corresponding to any desired field in an 8-field PAL sequence from one stored field or picture of a PAL signal

DETAILED DESCRIPTION We claim: 1.
A method of deriving a PAL color television signal corresponding to any field in an 8-field PAL sequence from one stored field or picture of a PAL signal, comprising: providing a first selected combination of signals from more than one line of said stored field to form a first part of said signal containing at least the low-frequency components thereof; separately providing a second selected combination of signals from more than one line of said stored field to form a second part of said signal containing only chrominance components thereof such that successive fields have the sub-carrier phase appropriate to the respective successive fields of a PAL signal; and combining said first and second parts to form said derived signal.
2.
A method according to claim 1, for deriving a PAL sequence from one stored field, in which for alternate ones of the fields the said low-frequency part of each line comprises the average of two adjacent stored lines.
3.
A method according to claim 1, wherein for at least some fields of the sequence the said chrominance part of the signal is formed by combining stored signals which are two lines apart.
4.
A method according to claim 3, wherein for at least some fields of the sequence the said chrominance part of the signal is formed by subtracting stored signals which are two lines apart, and halving the resultant.
5.
A method according to claim 1 wherein said first and second parts of the signal are formed in accordance with the following table:
TABLE I
______________________________________
State First Part Second Part
______________________________________
1 1/2(Z.
sup.
-313 + Z.
sup.
-312)
1/2(Z.
sup.
-314 - Z.
sup.
-312)
2 Z.
sup.
-625 1/2(Z.
sup.
-624 - Z.
sup.
-626)
3 1/2(Z.
sup.
-937 + Z.
sup.
-938)
1/2(Z.
sup.
-938 - Z.
sup.
-936)
4 Z.
sup.
-1250 -Z.
sup.
-1250
5 1/2(Z.
sup.
-1562 + Z.
sup