Abstract: This work proposes the use of the external wavelet transform (EWT) and the scalable binary description (S-BiD) technique to reduce the memory requirement and the processing time for wavelet-based image compression methods, in the stage of the wavelet transform as well as the quantization and coding of wavelet coefficients. With EWT, one performs the wavelet transform on an image stored in a less expensive but slower buffer with the help of a small fast cache. With the S-BiD technique, wavelet coefficients are partitioned into wavelet blocks. Each block is small enough to be fetched into the cache to be coded completely. Wavelet coefficients are quantized into a set of interleaved bit-streams that describe three layers in the quantization hierarchy, i.e. blocks, subbands and coefficients, respectively. The resulting codec finds wide applications. It can be easily implemented in a DSP or used to compress a very large image without tiling. It can generate good compressed images even with a cache memory less than 4 Kbyte. With a cache memory of 16 Kbyte, its PSNR performance is comparable with all other codecs while it has a very fast coding speed. The maximum size of the wavelet block that can be processed is limited by the size of the cache memory. The coding efficiency of this codec increases with a larger block size.!7
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