Masahiro Iwahashi

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While conventional DCT outputs real numbers and it is not suitable for lossless coding of images, the integer DCT (Int-DCT) outputs integer numbers and can serve as a lossless coding and lossy coding compatible to the conventional DCT. Recently, our group has proposed an optimum assignment method of word length of multipliers in the Int-DCT assuming(More)
Describes the development of a technique for subband image coding called the symmetric extension method which utilizes the nature of a symmetrically extended image to achieve high quality coding. There are, however, some restrictions on the usable subband coding system. The development is done based on the property of a symmetrically extended signal in the(More)
SUMMARY In this paper, we propose a new one-dimensional (1D) integer discrete cosine transform (Int-DCT) for unified lossless/lossy image compression. The proposed 1D Int-DCT is newly designed to reduce rounding effects by minimizing number of rounding operations. The proposed Int-DCT can be operated not only lossless coding for a high quality decoded image(More)
In this report, we propose a reversible two dimensional (2D) discrete wavelet transform (DWT) compatible to an irreversible DWT such as the 9-7 DWT for lossy coding in the JPEG 2000. All the filters and scalings are factorized into lifting steps, and signals are rounded into integers, so that the proposed DWT becomes reversible and applicable to lossless(More)
— This report proposes two layered bit depth scalable coding methods for high dynamic range (HDR) images expressed in floating point data format. From the base layer bit stream, low dynamic range (LDR) images are decoded. They are tone mapped appropriately for human eye sensitivity, and shortened to a standard bit depth, e.g. 8 [bit]. From the enhance layer(More)
Recently, the integer DCT (Int-DCT), which has the rounding operations in the lifting structure, is attracting many researchers' attention as an effective method for DCT based lossy / lossless unified coding. So far, focuses of the previous reports relevant to the Int-DCT have been limited to a few topics such as how to reduce the number of multipliers with(More)
— In this paper, a new structure of three dimensional integer rotation transform is proposed. The number of rounding operations is reduced from nine to four by introducing multi input lifting branches. Furthermore, the best combination of order of input signals is determined to avoid singular points of multiplier coefficients in the lifting branches. As a(More)