HP Labs Technical Reports
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Embedding Companders in JPEG Compression
Keyword(s): image compression, JPEG, companding
Abstract: The use of a compander (compressor-expander) in conjuction with scalar uniform high-resolution quantization, so as to obtain an overall effect of an improved nonuniform quantization, has been widespread for many years and embedded in standards of digitization and compression of audio waveforms (u-law in the U.S., and A-law in Europe). However, there is almost no reported work on its usefulness in still image and motion picture coding. In this work, we are making an attempt to embed companders in the JPEG algoirithm and our results show considerable improvement (10-25%) in compression ratio for large PSNR's. Strictly speaking, the new scheme is not standard compliant. However, with suitable preperocessing and postprocessing it can be imple- mented in a standard compliant manner. Also, the results of this research might be useful for the quantization part of future standards such as JPEG 2000.
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