The Research Of Pre-processing In Video Coding Of Videophone

As People's Daily communication tools, telephone is widely used with its convenient, but ordinary telephone is only "hear its voice, not only the person". With the rapid development of the multimedia and communication technology, videophone has broken the traditional mode of conversation and realized the simultaneous transmission of voice and video. Because of the huge amount of information, video has always been a major obstacle to communication. Although the communication network, storage media are gradually to the high speed, high capacity, but communication has become increasingly extensive common demand of the whole society.Therefore, channel bandwidth never enough. In the existing bandwidth limited (usually below 32kb/s), how to realize the data in the videophone video compression and high quality transmission is always people for many years. Therefore, very low bit rate video compression technology has important actual significance.At very low bit rate, there are usually two ways to realize the reliable videophone video transmission. First one is to reduce the image quality, the second it is to reduce activities smoothness. The paper proposes adding pre-processing before video encoding. It can be achieved compromise between image quality and smoothness.. The human eye is more sensitive to the face than the background. The pre-processing technique makes full use of such visual characteristics, and filter the high frequency of background .The proposed algorithm can improve compression ratio to a great extend without sacrificing subjective quality of face area , and at a same compression rate , the subjective quality of face area using pre-processing technique is obviously better than that of original compression scheme.The pre-processing method used in video coding of videophone proposed by the paper find out the face region through face detection and filter on the non-face region. The results show that in the fixed transmission rate, the pre-processing method improves the quality of face region of compressed video; in the fixed QP, the pre-processing method greatly reduces the bit rate and maintains the quality of the face region of compressed image.