MPEG video encoding based on assigning a high information priority to the focused region

When a picture is compressed in MPEG video, the image quality of important regions is maintained without changing the total amount of information; this is done by assigning a high information priority to the important regions. Therefore, the present paper proposes a method to modify a quantizer scale according to importance estimated by a depth of focus quantity. Image quality of an important region does not deteriorate much even if the total amount of information is decreased. Moreover, in television broadcasting, subtitles are usually in focus, so the proposed method can extract subtitle regions and give more priority to them.