Method and system for performing PAL chroma two-line vertical combing

A system for performing combing for PAL chroma data for a display having a plurality of lines, the display capable of depicting a frame including a horizontal boundary having a top edge and a bottom edge, a top line of the plurality of lines at the top edge of the horizontal boundary, a bottom line of the plurality of lines at the bottom edge of the horizontal boundary, the system comprising:

• a feedback multiplexer having a first input, a second input and a first output, the first input receiving luma data for a current line;
• a first line delay having a first delay input and a first delay output, the first delay input coupled with the first output;
• a second line delay having a second delay input and a second delay output, the second delay input coupled to the first delay output, the second delay output coupled with the second input;
• a feed forward multiplexer having a third input, a fourth input and a second output, the third input receiving the luma data for the current line, the fourth input coupled with the second delay output;
• the feedback multiplexer being controlled to provide fedback chroma data from the second input to the first output when the current line is the top line and to provide the chroma data for the current line from the first input to the first output otherwise, the feed forward multiplexer being controlled to provide fed forward chroma data from the fourth input to the second output when the current line is the bottom line and to provide the chroma data from the current line to the second output otherwise.

A method for providing a system for performing combing for PAL chroma data for a display having a plurality of lines, the display capable of depicting a frame including a horizontal boundary having a top edge and a bottom edge, a top line of the plurality of lines at the top edge of the horizontal boundary, a bottom line of the plurality of lines at the bottom edge of the horizontal boundary, the method comprising the steps of:

• (a) providing a feedback multiplexer having a first input, a second input and a first output, the first input receiving luma data for a current line;
• (b) providing a first line delay having a first delay input and a first delay output, the first delay input coupled with the first output;
• (c) providing a second line delay having a second delay input and a second delay output, the second delay input coupled to the first delay output, the second delay output coupled with the second input;
• (d) providing a feed forward multiplexer having a third input, a fourth input and a second output, the third input receiving the luma data for the current line, the fourth input coupled with the second delay output;
• the feedback multiplexer being controlled to provide fedback chroma data from the second input to the first output when the current line is the top line and to provide the chroma data for the current line from the first input to the first output otherwise, the feed forward multiplexer being controlled to provide fed forward chroma data from the fourth input to the second output when the current line is the bottom line and to provide the chroma data from the current line to the second output otherwise.