Method and circuit for detecting disappearance of logo pattern

A method for detecting disappearance of a pattern, implemented in a displaying apparatus and used to detect whether a fixed-still pattern in dynamic displayed images on the displaying apparatus disappears, wherein plural images are continuously displayed in a time sequence, the method for detecting disappearance of a pattern comprising:

• dividing each of the images into a plurality of blocks in a space sequence, wherein it is detected whether the disappearance of the fixed-still pattern happens to each of the blocks currently selected for processing respectively, comprising:
• analyzing a pattern characteristic parameter which represents the fixed-still pattern in the block and checking whether the pattern characteristic parameter fast decreases from at least greater than a high level to at least less than a low level, as a first state transition;
• calculating a sum of absolute difference (SAD) values for all of the pixels of a previous image and a current image in the block and checking whether the sum of the SAD values fast increases from at least less than the low level to at least greater than the high level, as a second state transition;
• and
• when the first state transition and the second state transition occur simultaneously, determining that the fixed-still pattern disappears in the display;
• and
• continuously carrying out the above steps on each of the rest blocks to detect whether the fixed-still pattern disappears.

A circuit for detecting disappearance of a pattern, used to detect whether a fixed-still pattern in dynamic displayed images disappears, comprising:

• a fixed-still pattern detecting unit, for detecting whether the dynamic displayed images contain the fixed-still pattern;
• and
• a fixed-still pattern disappearance detecting unit, coupled to the fixed-still pattern detecting unit, for detecting whether the fixed-still pattern disappears in a predetermined time, wherein the fixed-still pattern disappearance detecting unit executes multiple functions which comprises:
• analyzing a pattern characteristic parameter which represents the fixed-still pattern from each of images continuously displayed in a time sequence and checking whether the pattern characteristic parameter fast decreases from at least greater than a high level to at least less than a low level, as a first state transition;
• calculating a sumof absolute difference (SAD) values for all of the pixels between a previous image and a current image and checking whether the sum of the SAD values fast increases from at least less than a low level to at least greater than a high level, as a second state transition;
• and
• when the first state transition and the second state transition occur simultaneously, determining that the fixed-still pattern disappears in the display.