In this paper, an image compression scheme is proposed, based on discrete cosine transform (DCT). This scheme is a hybrid method, which combines vector quantization (VQ) and differential pulse code modulation (DPCM). This scheme begins with transforming image from spatial domain to frequency domain using DCT. Then the block data is transformed into a vector according to zigzag order, and then t...

A method for efficient quantization of speech spectral models is proposed. The impulse response of the model is coded in two spectral subbands of unequal width. The distortion measure used is a squared error between impulse responses. The quality obtained at 22 bits per frame is as good as that of Split Vector Quantization of Line Spectral Frequencies at 24 bits per frame.

Formerly, once the audio data is compressed, transcoding is used to scale the bit rate, where decoding and re-encoding are taken place. Therefore, data manipulation of coded data has been very complex and time consuming work. In this paper, we describe three algorithms for bit rate scaling on coded MPEG data domain. One is bandwidth limitation method cutting higher frequency components until ta...

This paper deals with public-key steganography in the presence of a passive warden. The aim is to hide secret messages within cover-documents without making the warden suspicious, and without any preliminar secret key sharing. Whereas a practical attempt has been already done to provide a solution to this problem, it suffers of poor flexibility (since embedding and decoding steps highly depend ...

In this paper we examine the possibility of applying fixed-lag smoothing techniques to trellis coded quantization (TCQ). For this application, we exploit the tree structure of the predictive TCQ (P-TCQ). We apply the (M,L) algorithm for searching the tree and Kalman smoother to find the smoothed estimates of the data. The performance of the resulting smoothed TCQ (S-TCQ) is compared to that of ...

In this work, we present coding techniques that enable progressive transmission when trellis coded quantization (TCQ) is applied to wavelet coefficients. A method for approximately inverting TCQ in the absence of least significant bits is developed. Results are presented using different rate allocation strategies and different entropy coders. The proposed wavelet-TCQ coder yields excellent codi...

Considerable research attention has been directed towards speech and audio coding algorithms capable of producing high quality coded speech and audio, however few of these use signal representations which account for temporal as well as spectral detail. This paper presents a new technique for 16 kHz wideband speech and audio coding, whereby analysis and synthesis are performed using a linear ph...

In this paper, we propose a delay constrained spatio-temporal video rate control method for lossy channels where the effective channel rate available to the video encoder is time-varying. Target bit-rate constraint for encoding is derived, which guarantees in-time delivery of video frames. By using empirically obtained rate-quantization and distortionquantization relations of video, the distort...

A psychovisually-based quantization strategy for wavelet coded images is proposed. The quantization strategy is based on the results of a psychovisual evaluation to quantify sensitivities to suprathreshold distortion caused by wavelet coefficient quantization in natural images. Quantizer step sizes to produce a minimum noticeable distortion are paremeterized in terms of subband standard deviati...