Control methods of sample adaptive offset (sao) filtering and related image processing systems thereof

An image processing system, comprising:

• an image input device, obtaining a video signal, wherein the video signal includes at least one group of picture (GOP) and the GOP has a plurality of frames, each of which having a plurality of coding tree units (CTUs);
• a sample adaptive offset (SAO) On/Off control device connected to the image input device;
• a de-blocking filter coupled to the SAO On/Off control device;
• and
• an SAO filter connected to the de-blocking filter for performing an SAO filtering,
• wherein the SAO On/Off control device receives the video signal, determines whether current frame is an intra-picture frame (I frame), turns on the SAO filter to enable the SAO filter to perform the SAO filtering on the current frame and determines a CTU ratio of the CTUs being not performed with the SAO filtering for the current frame in response to determining that the current frame is the I frame, and selectively turns off the SAO filter from next non-I frame based on the CTU ratio, such that the SAO filter does not perform the SAO filtering on subsequent non-I frames in the GOP including the current frame.