Hydroacoustic image compression method based on discrete wavelet transform under excessive bit error rate

Abstract

The present invention discloses an underwater sound image compressing method based on discrete wavelet conversion under high error bit ratio, including the following steps: 1) to statistical analysis the child band energy of image wavelet parameter, and obtain wavelet parameter child band energy statistical table by implementing three-layer decomposing to the underwater sound image through dual orthogonal CDF9 / 7 wavelet group; 2) image quantification; 3) encoding and decoding, to implement compress encoding to the quantification parameter after the three-layer decomposing. The encoding process includes the following steps: (1) to implement definite length encoding to the parameter of the child band LL3, HL3, LH3, HL2 and LH2; (2) to divide the child band LH1 into sixteen subblocks of sixteen by sixteen, each subblock uses the front 128 zero journey encoding mates, the journey number and the non zero value is defined by 2bits and 3bits separately; (3) to abnegate the encoding to the child band of HH3, HH2, HH1 and HL1. The method of the present invention counterpleas high error bit ratio, the image quality after compressing is very good.

Description

technical field [0001] The invention relates to an image compression method, in particular to an underwater acoustic image compression method based on discrete wavelet transform under high bit error rate. Background technique [0002] Underwater acoustic coherent communication technology transmits images, language, instructions and data, and source coding technology should be used. In order to transmit images quickly, images need to be compressed, and there are often bit errors during transmission. Common image compression methods, such as D.S.Taubman, M.W.Marcellin's document 1: "JPEG 2000 Image compressionfundamentals, standards and practice, Boston: Kluwer Academic Publishers, 2003" The method disclosed in is working at a very low bit error rate (Bit Error Rate, referred to as BER), for example, the bit error rate is 10 -6 , making it difficult to use this method to transmit images in underwater acoustic channels, because the BER in underwater acoustics is relatively hig...

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Problems solved by technology

However, this article does not disclose the underwater acoustic image compression method. The method in this document cannot be directly used for underwater acoustic image compression because of the characteristics of underwater acoustic images: underwater acoustic images are anisotropic. For example, for sounding side-scan sonar Image, its resolution along the course (called the vertical direction) becomes lower with the increase of the distance, and the resolution perpendicular to the course (called the horizontal direction) becomes higher with the increase of the distance; the resolution of the two directions is very different, This is different from optical images; hydroacoustic images are also less correlated than optical images

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