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In this paper we propose two image watermarking algorithms, which are robust to cropping operation using self-synchronization mechanism. In both algorithms, the watermark sequence is firstly encoded by non-cyclic Low Density Parity Check Codes (LDPC) and then it is embedded into the block-wised Discrete Cosine Transform (DCT) coefficients using the Quantization Index Modulation (QIM) algorithm. In...
In this paper, we focus on the channel characteristics of audio files when MPEG 1 layer III (MP3) compression is applied. We propose a data hiding scheme which achieves 61.25 bits per second, around 39 bits of benefit than Cvejic which uses turbo codes. Our scheme embeds binary data on specific sub-bands in wavelet domain using dither modulation. Those specific sub-bands were found to be more robust...
In this paper we propose an adaptive data hiding method that divides the host image in suitable and ineligible blocks. This classification is based on the DCT energy features from the horizontal, vertical and diagonal frequency information. Only the suitable blocks are used for data embedding using quantization index modulation (QIM). After the composite image is attacked by JPEG compression, a desynchronization...
In this paper, we analyze audio watermarking methods based on quantization index modulation and low-density parity-check (LDPC) codes. We found that dither modulation (DM) can achieve better performance using half-rate Margulis LDPC code even better than some low-rate codes. Then, we propose a scheme based on LDPC codes and DM with distortion-compensation (DC) property which has a robustness benefit...
A new method for decoding low-density lattice codes is given, wherein the belief-propagation decoder messages are single Gaussian functions. Since the message can be represented by two numbers, a mean and a variance, the complexity of this decoder is lower than previous decoders, which either quantized the mixture, or used a mixture of Gaussians. The computational complexity at the check node is also...
For decoding low-density parity-check (LDPC) codes on discrete memoryless channels, a method to quantize messages and to find message-passing decoding functions for the variable and check nodes is developed. These are used to obtain noise thresholds by density evolution. The message-passing decoding alphabet is restricted to be discrete with a fixed maximum alphabet size. Discrete quantization is...
A message-passing decoder for GF(q) low-density parity-check codes is defined, which uses discrete messages from a subset of all possible binary vectors of length q. The proposed algorithm is a generalization to GF(q) of Richardson and Urbanke's decoding "Algorithm E" for binary codes. Density evolution requires a mapping between the probability distribution spaces for the channel, variable...
A multilevel channel coding system using binary convolutional codes is proposed. This system achieves high coding gain. For example, we can obtain an 8-PSK system with rate R = 2/3, which has 6.02 dB coding gain over uncoded 4-PSK and is implemented as easily as Ungerboeck's system with total encoder memory K = 4.
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