First and second filter decision values are calculated for a pixel block in a video frame. The first filter decision value is representative of how smooth pixel values in a first line of pixels in the block and in a corresponding first line of pixels in a neighboring pixel block in the video frame are in a direction parallel to a filtering direction. The second filter decision value is representative of how close pixel values in a current line of pixels in the block approximate a flat line and how close pixel values in a corresponding current line of pixels in the neighboring block approximate a flat line. The two filter decision values are compared to respective thresholds and a strong de-blocking filter is selected for the current line if the filter decision values are below the thresholds, otherwise a weak de-blocking filter is selected to combat any blocking artifacts.