Somchart Chokchaitam

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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)
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)
Recently, the integer DCT (Int-DCT), which transforms an integer input to an integer output, is attracting many researchers' attention as an effective method for DCT-based lossy/lossless unified coding. So far, there are many reports relevant to the Int-DCT, but they have been limited to a few topics such as how to reduce the number of multipliers with the(More)
This report proposes a new coding method, which realizes lossless, near-lossless and lossy coding with a unified single algorithm. The method is based on a lifting-structured lossless DCT, which maps an "integer" input vector to also an "integer" output vector. The proposed method can be used as not only a high performance "lossless" encoder but also a(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)
The lifting structured wavelet transform (lifting wavelet) attracts researchers' attention as a key technology to a lossless and lossy unified coding system of digital image data. For VLSI circuit implementation, multiplier coefficients in the transform must be truncated into finite word length binary values. This report investigates how to appropriately(More)
In this report, we propose lossless/lossy coding gain as a new objective criterion to theoretically evaluate lossless and lossy coding performance of the lossless/lossy wavelet (LLW). The proposed lossless/lossy coding gain consists of three parameters: " lossless coding gain " , " quantization-lossy coding gain " and " rounding errors ". Performances of 15(More)
Recently, we proposed a new multiplierless 1D Int-DCT modified from our existing Int-DCT by approximating floating multiplications to bit-shift and addition operations. The multiplierless 1D Int-DCT can be well operated both lossless coding and lossy coding. However, our multiplierless 1D Int-DCT is not focused on how to assign word-length for(More)