This letter proposes improvement to the previously presented watermarking method which spreads an ID pattern with a random sequence and embeds it throughout the spatial domain of an image. The proposed method can extract embedded watermarks without an original image even from images converted by brightness/contrast conversion, edge-enhancement, posterization and JPEG compression.

We propose discrimination method of synthetic speech using pitch pattern of speech signal. By applying the proposed synthetic speech discrimination system as pre-process before the conventional HMM speaker verification system, we can improve the safety of conventional speaker verification system against imposture using synthetic speech. The proposed method distinguishes between synthetic speech and natural speech according to the pitch pattern which is distribution of value of normalized short-range autocorrelation function. We performed the experiment of user verification, and confirmed the validity of the proposed method.

Orchard coding scheme is a kind of convolutional coding system of rate (n01)/n0. In this system. Calculation of parity bits is over perviously calculated parity bits as well as information bits. This article presents a new class of orchard codes which correct double bit errors and single byte errors within a constraint length. The rate of the codes is (n01)/n0 and the constraint length is n0(4n0+1) bits. A byte is group of n0 bits. In the proposed codes, the generation of a present parity bit is affected by the information bits and the parity bits for past 2n0 clock times. The decoder generates a syndrome sequence and errors are corrected using the syndrome pattern. An error propagation occurs only when the punctuation of a syndrome pattern of length 4n0+1 is erroneous, but if the successive 4n0 zero-bits appear in the syndrome sequence, the error propagation does not occur beyond that.

In this letter, we propose a simple reversible watermarking method for JPEG images using the characteristics of JPEG compression. The method embeds a watermark into a JPEG image, and it extracts the watermark from the watermarked JPEG image and at the same time can recover the watermarked JPEG image to an original unwatermarked JPEG image. Moreover we investigate the number of embeddable blocks, the quality of watermarked images, and the increase of file-size by embedding a watermark.

This letter proposes extended single parity check product codes and presents their empirical performances on a Gaussian channel by belief propagation (BP) decoding algorithm. The simulation results show that the codes can achieve close-to-capacity performance in high coding rate. The code of length 9603 and of rate 0.96 is only 0.77 dB away from the Shannon limit for a BER of 10-5.

In this paper, a type hybrid ARQ scheme with Adaptive Forward Error Correction (ARQ/AFEC) using BCH codes is proposed and analyzed. The basic idea in the proposed type hybrid ARQ/AFEC scheme is to increase the error-correcting capability of BCH code according to channel state using incremental redundancy. The incremental redundancy is the remainder ai(x) of an information frame f(x) of length n divided by a minimum polynomial mi(x) of α2i-1, where α is a primitive element of finite field GF(2l). Let gi(x) be the product of mj(x) (j=1, 2, , i) and let ci(x) be the remainder of f(x) divided by gi(x). The polynomial ci(x) is obtained from the remainders ai(x) and ci-1(x) since mi(x)and gi-1 (x) are relatively prime. Since f(x) + ci(x) is divided by gi(x), f(x) + ci(x) is the codeword of an i-error-correcting BCH code when n2l-1. So, the errors less than or equal to i bits in f(x) can be corrected if ci(x) has no error.

This paper proposes a new steganographic method utilizing features of JPEG compression. The method embeds secret information using the number of zeroes in a block of quantized DCT coefficients in minimum coding units (MCU) of JPEG images. In the method, we can embed secret information into JPEG images with degradation like that by JPEG compression. Furthermore, the method causes little change of the histogram of quantized DCT coefficients, so it is hard to perceive secret information embedded by the method. The method mainly modifies boundaries between zero and non-zero DCT coefficients, so we can use the low frequency side of DCT coefficients for another steganographic method.

In this paper, we propose a new watermarking method which spreads an ID pattern with specific sequences and embeds it throughout the spatial domain of an image. A set of the sequences is a key for extracting the ID pattern. As an ID pattern is spread throughout an image, we can extract the ID pattern from a part of the image, that is a clipped image. We can also confirm authenticity by extracting the same ID pattern from several parts of an image. The proposed method is robust to StirMark, which is a benchmark tool to test robustness of watermarked images, as well as disturbance by noise addition and common image processing operations such as edge-enhancement, brightness-contrast conversion, posterization, Gauss filtering, median filtering, gamma correction, JPEG compression and clipping.

This letter presents an automatic repeat request/adaptive forward error correction (ARQ/AFEC) hybrid system which adaptively alters the error-correcting capability according to channel state using a nonsystematic Reed-Solomon code. Frame efficiency is also presented.

The performance of APP (a posteriori probability) decoding algorithm which is well known as a soft decision decoding algorithm for majority logic decodable codes is further improved by iterating the algorithm one or more times. This letter shows that there exists the optimal non-zero threshold value of the decision function that minimizes the decoded error rate in two-pass APP decoding though the optimal threshold value in one-pass APP decoding is zero.

We proposed a soft-decision decoding algorithm for cyclic codes based on energy minimization principle. This letter presents the algorithm which improves decoding performance and decoding complexity of the previous method by giving more initial positions and introducing a new criterion for terminating the decoding procedure. Computer simulation results show that both the decoded block error rate and the decoding complexity decrease by this method more than by the previous method.

This paper presents a correlation-based watermarking method for video using the similarity of adjacent frames. In general, the adjacent frames of a video sequence is very similar. In the proposed scheme, we use an adjoining frame in detection process instead of an original image in the watermarking scheme of Cox et al. So the proposed method does not need an original video sequence in detection process. When a watermarked video sequence is attacked by overwriting copy or frame dropping, the pair of the frames that is not adjoining in an original video sequence is used in detection process. However, since a watermark is embedded in a part of each frame and embedding positions are different for each frame in the proposed method, we can detect the watermark even from an overwriting-copied video sequence and a frame-dropped video sequence. Experimental results show that the proposed method is robust against overwriting copy and frame dropping. Moreover, it is shown from experimental results that the method has robustness to low bitrate MPEG compression and StirMark attack.

It is necessary for anyone to be able to extract embedded index data without specific keys or secret information when index data are embedded into digital contents. In this paper, we propose a new data hiding technique for embedding index data into color images using wavelet transform. In our method, we prevent image quality from degrading by utilizing not specific keys but features of wavelet transform. The method extracts index data without specific keys and is tolerant of edge-enhancement, gamma correction, brightness conversion and lossy image compression such as JPEG compression.

In the acquisition of projection data of X-ray CT, logarithm operation is indispensable. But noise distribution is nonlinearly projected by the logarithm operation, and this deteriorates the precision of CT number. This influence becomes particularly remarkable when only a few photons are caught with a detector. It generates a strong streak artifact (SA) in a reconstructed image. Previously we have clarified the influence of the nonlinearity by statistical analysis and proposed a correction method for such nonlinearity. However, there is a problem that the compensation for clamp processing cannot be performed and that the suppression of SA is not enough in photon shortage state. In this paper, we propose a new technique for correcting the nonlinearity due to logarithm operation for noisy data by combining the previously presented method and an adaptive filtering method. The technique performs an adaptive filtering only when the number of captured photons is very few. Moreover we quantitatively evaluate the influence of noise on the reconstructed image in the proposed method by the experiment using numerical phantoms. The experimental results show that there is less influence on spatial resolution despite suppressing SA effectively and that CT number are hardly dependent on the number of the incident photons.

This letter proposes a method which can embed index data such as memos into JPEG images. The method embeds digital watermarks using the quantitative relation between quantized DCT coefficients in JPEG images. In the method, we can embed extra data to represent index data and can extract the index data without parameters used in embedding process. Furthermore, the method is tolerant of JPEG recompression and prevents the degradation of image quality by rewriting index data.

We propose a novel soft-decision decoding algorithm for cyclic codes based on energy minimization principle. The well-known soft-decision decoding algorithms for block codes perform algebraic (hard-decision) decoding several times in order to generate candidate codewords using the reliability of received symbols. In contrast, the proposed method defines energy as the Euclidean distance between the received signal and a codeword and alters the values of information symbols so as to decrease the energy in order to seek the codeword of minimum energy, which is the most likely codeword. We let initial positions be the information parts of signals obtained by cyclically shifting a received signal and look for the point, which represents a codeword, of minimum energy by moving each point from several initial positions. This paper presents and investigates reducing complexity of the soft-decision decoding algorithm. We rank initial positions in order of reliability and reduce the number of initial positions in decoding. Computer simulation results show that this method reduces decoding complexity.

It is urgently required to protect copyrights of digital contents since the digital contents can be easily copied without degradation of quality. In this paper, we propose a new watermarking method which spreads an ID pattern with a random sequence and embeds it throughout the spatial domain of a color image. The random sequence is a key for extracting the ID pattern. As an ID pattern is spread throughout an image, we can extract the ID pattern from a part of the image, that is clipped image. We can also confirm authenticity by extracting the same ID pattern from several parts of an image. The proposed method is robust to disturbance by noise addition and image conversion such as brightness-contrast conversion and JPEG compression.

It is necessary condition for digital watermarking method for embedding memos or index data into digital photograph and so on that anyone can extract embedded data without specific keys or secret information. In this paper, we propose a data hiding technique for embedding index data into color images using wavelet transform. The proposed method keeps image quality and robustness against JPEG compression and general image processing using quantitative relation of wavelet coefficients.

This letter presents the empirical error performance of combining method of a binary numerical code and a single error correcting code on Gaussian channel by belief propagation (BP) decoding algorithm. The numerical codes mentioned here are constructed with any symbol value and have the parity check matrices in reduced-echelon form whose elements are binary (0 and 1). The simulation results show that the method yields good decoding error performance for medium code lengths.