A video processing system comprises a video processor and an output buffer. When a new frame is to be written to the output buffer, the video processing system determines (12) for at least a portion of the new frame whether the portion of the new frame has a particular property. When it is determined that that the portion of the new frame has the particular property (14), when a block of data representing a particular region of the portion of the new frame is to be written to the output buffer, it is compared to at least one block of data already stored in the output buffer, and a determination is made whether or not to write the block of data to the output buffer on the basis of the comparison. When it is determined that the portion of the new frame does not have the particular property (16), the portion of the new frame is written to the output buffer.