Steerable Discrete Cosine Transform

In image compression, classical block-based separable transforms tend to be inefficient when image blocks contain arbitrarily shaped discontinuities. For this reason, transforms incorporating directional information are an appealing alternative. In this paper, we propose a new approach to this problem, namely a discrete cosine transform (DCT) that can be steered in any chosen direction. Such transform, called steerable DCT (SDCT), allows to rotate in a flexible way pairs of basis vectors, and enables precise matching of directionality in each image block, achieving improved coding efficiency. The optimal rotation angles for SDCT can be represented as solution of a suitable rate-distortion (RD) problem. We propose iterative methods to search such solution, and we develop a fully fledged image encoder to practically compare our techniques with other competing transforms. Analytical and numerical results prove that SDCT outperforms both DCT and state-of-the-art directional transforms

Mixed-radix discrete cosine transform

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Handwritten Arabic character recognition: which feature extraction method?

Recognition of Arabic handwriting characters is a difficult task due to similar appearance of some different characters. However, the selection of the method for feature extraction remains the most important step for achieving high recognition accuracy. The purpose of this paper is to compare the effectiveness of Discrete Cosine Transform and Discrete Wavelet transform to capture discriminative features of Arabic handwritten characters. A new database containing 5600 characters covering all shapes of Arabic handwriting characters has also developed for the purpose of the analysis. The coefficients of both techniques have been used for classification based on a Artificial Neural Network implementation. The results have been analysed and the finding have demonstrated that a Discrete Cosine Transform based feature extraction yields a superior recognition than its counterpart

IMPLEMENTASI AUDIO WATERMARKING MENGGUNAKAN DISCRETE COSINE TRANSFORM (DCT) IMPLEMENTATION OF AUDIO WATERMARKING USING DISCRETE COSINE TRANSFORM (DCT)

ABSTRAKSI: Watermarking merupakan suatu teknik untuk menyembunyikan suatu data digital pada data digital yang lain. Salah satu implementasi watermarking adalah audio watermarking. Teknologi watermarking pada data audio digital terbagi menjadi dua, yaitu temporal watermarking, menyembunyikan watermark langsung ke dalam audio dalam domain waktu dan spectral watermarking, adanya proses transformasi dari domain waktu ke domain frekuensi. Transformasi yang biasa digunakan misalnya DCT, FFT, DWT, dll. Namun pengimplementasian metode transformasi DCT dalam audio watermarking masih jarang dijumpai. Dalam tugas akhir ini diimplementasikan teknik audio watermarking, yaitu teknik menyisipkan suatu data digital berupa teks ke dalam file audio digital yang berformat *.wav dengan menggunakan transformasi DCT (Discrete Cosine Transform). Terhadap audio terwatermark dilakukan pengujian kualitas secara obyektif dan subyektif serta diadakan pengujian ketahanan watermark terhadap beberapa proses pengolahan sinyal. Dari pengujian yang telah dilakukan secara obyektif dan subyektif terhadap sistem audio watermarking menggunakan DCT diperoleh hasil bahwa audio terwatermark mempunyai kualitas menyerupai file audio aslinya bila nilai SNR yang dihasilkan diatas 78,538 dB dan kualitas audio watermark tergantung nilai koefisien pengali dan panjang teks. Hasil pengujian menunjukkan bahwa nilai koefisien pengali 0,001 menghasilkan kualitas audio terwatermark yang mendekati aslinya. Sedangkan dari pengujian ketahanan watermark terhadap pengolahan sinyal didapatkan bahwa dalam sistem audio watermarking menggunakan DCT, tingkat ketahanan watermark berupa teks sangat rentan terhadap perubahan.Kata Kunci : Audio Watermarking, Discrete Cosine TransformABSTRACT: Watermarking is technique to hide a digital data into another digital data. Audio watermarking is an implementation of watermarking. Digital audio watermarking technology consist of temporal watermarking which is directly hide watermark into audio on time domain and spectral watermarking which is use transformation from time domain into frequency domain. Commonly used transformations are DCT, FFT, DWT, etc. However implementation of employing the DCT method for audio watermarking still rare to meet. Audio watermarking a technique to embed digital data (in this case text) into digital audio file (WAV extension) was implemented on this thesis using Discrete Cosine Transform (DCT). Objective and subjective quality test was conducted into watermarked audio. Watermark robustness test against some digital signal processing also conducted. From objective and subjective test result to DCT based audio watermarking system, I conclude that watermarked audio have almost equal quality compared to original audio file if SNR resulted is above 78,538 dB and watermarked audio quality depend on multiplier coefficient and the text length. Test result show that on multiplier coefficient 0,001 quality of audio file close to it’s original. Meanwhile from watermark robustness test against digital signal processing I conclude that on DCT based audio watermarking system, robustness level on text watermark is very susceptible with alteration.Keyword: Audio Watermarking, Discrete Cosine Transfor

Evolution of the discrete cosine transform using genetic programming

Compression of 2 dimensional data is important for the efficient transmission, storage and manipulation of Images. The most common technique used for lossy image compression relies on fast application of the Discrete Cosine Transform (DCT). The cosine transform has been heavily researched and many efficient methods have been determined and successfully applied in practice; this paper presents a novel method for evolving a DCT algorithm using genetic programming. We show that it is possible to evolve a very close approximation to a 4 point transform. In theory, an 8 point transform could also be evolved using the same technique