Circuits and Systems for Video Technology, IEEE Transactions on

A method of coding super high definition (SHD) still images based on vector quantization of wavelet coefficients is proposed. A compression scheme for SHD images should achieve data compression without any visible picture quality deterioration. We demonstrate that the proposed method meets this requirement. In this coding technique, each vector of wavelet coefficients is coded by a series of vectors of decreasing magnitudes, resulting in a successive approximation process. It also exploits the structural similarities among the bands. This provides efficient coding together with the ability to guarantee arbitrary distortion levels for each band, which can be exploited to achieve subjectively optimum performance. Conventional image compression techniques such as transform, sub-band, and vector quantization have already been tested for the coding of SHD images. Simulation results show that the proposed method outperforms the other SHD image coding methods reported in the literature View full abstract»

A scalable implementation scheme for multirate finite impulse response (FIR) filters is presented in this paper. The implementation scheme can reduce the time and area cost of a multirate FIR filter simultaneously. According to the throughput requirement, the proposed scheme achieves a minimum-area design with specified speed. Furthermore, by employing the scalable implementation scheme, we also propose an efficient design technique for subband filter banks View full abstract»

A block-based gradient descent search (BBGDS) algorithm is proposed in this paper to perform block motion estimation in video coding. The BBGDS evaluates the values of a given objective function starting from a small centralized checking block. The minimum within the checking block is found, and the gradient descent direction where the minimum is expected to lie is used to determine the search direction and the position of the new checking block. The BBGDS is compared with full search (FS), three-step search (TSS), one-at-a-time search (OTS), and new three-step search (NTSS). Experimental results show that the proposed technique provides competitive performance with reduced computational complexity View full abstract»

We note that the arrangement of the rows or the block wavelet transform (BWT) matrix as given by Cetin, Gerek and Ulukus (see ibid. vol.3, no.6, p.433, 1993) is not in an increasing order of frequency as implied by the equations and figures in the same paper. The rows of the matrix are rearranged to follow an increasing order of frequency View full abstract»

An efficient video coding scheme is presented as an extension of the MPEG-2 standard to accommodate the transmission of multiple viewpoint sequences on bandwidth-limited channels. With the goal of compression and speed, the proposed approach incorporates a variety of existing computer graphics tools and techniques. Construction of each viewpoint image is predicted using a combination of perspective projection of three-dimensional (3-D) models, texture mapping, and digital image warping. Immediate application of the coding specification is foreseeable in systems with hardware-based real-time rendering capabilities, thus providing fast and accurate constructions of multiple perspectives View full abstract»

Scalability refers to the ability to modify the resolution and/or bit rate associated with an already compressed data source in order to satisfy requirements which could not be foreseen at the time of compression. A number of researchers have already demonstrated the feasibility of efficient scalable image and video compression. The principle focus of this paper is to describe data structures for highly scalable compressed video, which are able to support simple, generic scaling approaches for both constant bit rate and constant distortion scaling criteria. Interactive video material presents particular challenges when the data stream is to be scaled to maintain an approximately constant level of distortion, rather than just a constant bit rate. Special attention is paid, therefore, to the development of generic, robust scaling algorithms for such applications. The data structures and scaling methodologies developed are particularly appealing for the distribution of highly scalable compressed video over heterogeneous media, because they simultaneously support both variable bit rate (VBR) and constant bit rate (CBR) services with a wide range of available service qualities, using only simple, generic mechanisms for scaling. The performance of the proposed scaling methodologies is experimentally investigated using a highly scalable video compression algorithm, which is able to achieve comparable compression performance to that of the inherently nonscalable MPEG-1 compression standard View full abstract»

The goal of this paper is to study the application of two-dimensional (2-D) finite-precision infinite impulse response (IIR) filters to enhanced National Television System Committee (NTSC) coding. It is well-known that suitable twoor three-dimensional (3-D) digital filtering greatly improves the quality of NTSC pictures by suppressing the interference between the luminance Y and the chrominances I, Q. Thus far, 2-D and 3-D finite impulse response (FIR) filters have been used to reduce or eliminate these cross effects. To achieve good performance, however, they require many coefficients. Since, in general, IIR filters need fewer coefficients to approximate a given magnitude response, we investigate the possibility of applying 2-D IIR filters to the NTSC encoding/decoding. We also study the feasibility of using digital filters for NTSC channel filtering; this would permit a digital-only encoder. To design suitable filters, we use a method based on multiple constraint optimization and simulated annealing. We propose a new implementation structure for the IIR filters that differs from the zero-phase FIR structure. We simulate the full NTSC coding chain and compare the resulting images for both filter types View full abstract»

This paper presents a new systolic architecture that can be used to realize the full-search vector quantization (VQ) encoder for high-speed applications. The architecture possesses the features of regularity and modularity, and is thus very suitable for VLSI implementation. For a codebook of size N and dimension k, the VQ encoder has an area complexity of O(N), a time complexity of O(k), and I/O bandwidth of O(k). It reaches a compromise between the hardware cost and speed performance as compared to existing systolic/regular VQ encoders. At the current state of VLSI technology, the proposed system can easily be realized in a single chip for most practical applications. In addition, it provides flexibility in changing the codebook contents and extending the codebook size, where the latter is achieved simply by cascading some identical basic chips. With 0.8 μm CMOS technology to implement the proposed VQ encoder for the case of N=256, K=16, and an input data wordlength of 8 bit, the chip requires a die size of about 5.5×8.9 mm² and is able for processing 6.25 M data vectors (or 100 M data samples) every second. These features show that the proposed architecture is attractive for use in high-speed image/video applications View full abstract»

We present a human face location technique based on contour extraction within the framework of a wavelet-based video compression scheme for videoconferencing applications. In addition to an adaptive quantization in which spatial constraints are enforced to preserve perceptually important information at low bit rates, semantic information of the human face is incorporated to design a hybrid compression scheme for videoconferencing since the human face is often the most important portion within a frame and should be coded with high fidelity. The human face is detected based on contour extraction and feature point analysis. An approximated face mask is then used in the quantization of the decomposed subbands. At the same total bit rate, coarser quantization of the background enables the face region to be quantized finer and coded with higher quality. Simulation results have shown that the perceptual image quality can be greatly improved using the proposed scheme View full abstract»

A new technique of adaptively classifying the scene content of an image block has been developed in the proposed perceptual coder. It measures the texture masking energy of an image block and classifies it into one of four perceptual classes: flat, edge, texture, and fine-texture. Each class has an associated factor to adapt the quantizer with the aim of achieving constant quality across an image. A second feature of the perceptual coder is the visual thresholding, a process that reduces bit rate by discarding subthreshold discrete cosine transform (DCT) coefficients without degrading the image perceived quality. Finally, further quality gain is achieved by an improved reference model 8 (RM8) intramode decision, which removes sticking noise artifacts from newly uncovered background found in H.261 coded sequences. Subjective viewing tests, guided by Rec. 500-5, were conducted with 30 subjects. Subjective results confirm the efficacy of the proposed classified coder over the RMS based H.261 coder in two ways: (i) it consistently produces better quality sequences (with a mean opinion score, MOS, of approximately 2.0) when comparing at any fix bit rate; and (ii) it achieves a bit rate saving of 35% when measuring at the same picture quality (i.e., same MOS) View full abstract»