Research On Transmission-Oriented Image Compression Algorithm In Colliery Security System

In colliery security system, the real-time transmission of monitoring image is very important for monitor center to get the status of coal mine at any moment, and it's significant for colliery security. Before transmission of monitoring image using the wireless network of colliery security system, we must compress the image as far as possible considering the bandwidth of the network.At present, most practical image compression algorithm are based on Discrete Cosine Transform (DCT), such as JPEG As for video sequence, most compression algorithm are based on spacial motion estimation and compensation, then make DCT to compensation difference and quantify the transform coefficients, such as MPEG-1, MPEG-2. However, as the compress ratio increases, block effect will appear on the resumed image.Wavelet transform has good characteristics that can localize space and frequency domain, which are suitable for describing the non-steady image signal, meet people's systematic characteristic of vision, so it receive more and more concerns in the field of video code.This dissertation is in light of low code rate requirement in wireless transmission, then researches and analyses the existing Joint image compression algorithm and video sequence compression algorithm, and compares the performance of every algorithm. This dissertation emphasis on the principle of video encode system based on wavelet domain, and analyses motion vectors estimation and compensation algorithm based on wavelet domain, also proposes improving algorithm, a kind of detection method of motion based on wavelet domain. Make motion detection on top low frequency band from wavelet decomposition and get the motion area on low frequency band. Search for the motion vector in this movement area. Because movement area is smaller relatively to entire low frequency band, speed of search motion vectors raise greatly. In addition, the division of the motion area has produced certain guidance function for search for the motion vector, which narrows the search area and prevents motion vector distortion.The motion vector on the top low frequency band is the basic vector for search for motion vector on other bands. Therefore, the estimation of this motion vector must be accurate. The proposal in this dissertation adopts the match criterion considering motion match on high-frequency band at the same level, has guaranteed the accuracy of motion vectors searches on top low frequency band.