A single-chip adaptive DPCM video codec

A differential pulse-code modulation (DPCM) video codec with two-dimensional intrafield prediction and adaptive quantizer is presented. An approach for the arithmetic implementation of the DPCM structure and the design of a test chip, fabricated in a 1.5 μm CMOS technology, is described. This is the first VLSI realization of a DPCM codec with adaptive quantizer. For the test chip transmitter or receiver mode, application as part of a three-dimensional interframe codec and processing of luminance or chrominance signals are optional. A line buffer and ten different quantizer characteristics are realized on-chip. Correct operation has been verified up to 26 MHz     

视频编码标准H.263+的新特征研究

介绍了视频编码标准H.263 可协商的编码选项，尤其对于其中的改进PB帆帧模式、片结构模式和前向纠错模式进行了较深入研究。     

Bit-rate control algorithm on video packet coding and its characteristics

A bit-rate control method based on a hybrid coding algorithm is proposed for packet video coding. Three types of bit-rate control modes, the constant bit-rate mode, the average bit-rate control mode and the free bit-rate mode, are investigated. According to the opinion test the latter two modes have an advantage in video quality over the constant bit-rate mode. A teleconference terminal, which includes this video codec, audio codec and packet adaptor, is implemented in actual hardware on High-speed Packet Switching system. On this system, video information are transmitted in UI frame (a packet format in X.25 protocol) at 64 K 800 Kbit/s.     

Introducing skip mode in distributed video coding

Although it was proven in the 1970s already by Wyner and Ziv and Slepian and Wolf that, under certain conditions, the same rate–distortion boundaries exist for distributed video coding (DVC) systems as for traditional predicting systems, until now no practical DVC system has been developed that even comes close to the performance of state-of-the-art video codecs such as H.264/AVC in terms of rate–distortion. Some important factors for this are the lower accuracy of the motion estimation performed at the decoder, the inaccurate modeling of the correlation between the side information and the original frame, and the absence in most state-of-the-art DVC systems of anything conceptually similar to the notion of skipped macroblocks in predictive coding systems.This paper proposes an extension of a state-of-the-art transform domain residual DVC system with an implementation of skip mode. The skip mode has an impact at two different places: in the turbo decoder, more specifically the soft input, soft output (SISO) convolutional decoder, and in the puncturing of the parity bits. Results show average bitrate gains up to 39% (depending on the sequence) achieved by combining both approaches.Furthermore, a hybrid video codec is presented where the motion estimation task is shifted back to the encoder. This results in a drastic increase in encoder complexity, but also in a drastic performance gain in terms of rate–distortion, with average bitrate savings up to 60% relative to the distributed video codec. In the hybrid video codec, smaller but still important average bitrate gains are achieved by implementing skip mode: up to 24%.     

OFDM-based turbo-coded hierarchical and non-hierarchicalterrestrial mobile digital video broadcasting

The feasibility of terrestrial digital video broadcast (DVB) to mobile receivers is studied and turbo coded performance enhancements are proposed. Initially, the MPEG-2 codec is subjected to a rigorous bit error sensitivity investigation, in order to assist in designing various error protection schemes for wireless DVB transmission. The turbo codec is shown to provide signal-to-noise ratio (SNR) performance advantages in excess of 5-6 dB over conventional convolutional coding both in terms of bit error rate and video quality. Our experiments suggested that-despite our expectations-multi-class data partitioning did not result in error resilience improvements, since a high proportion of relatively sensitive video bits had to be relegated to the lower integrity subchannel, when invoking a powerful low-rate channel codec in the high-integrity protection class. Nonetheless, DVB transmission to mobile receivers is feasible, when using turbo-coded OFDM transceivers at realistic power-budget requirements under the investigated highly dispersive fading channel conditions. It is interesting to note furthermore that the 5-6 dB SNR improvement due to turbo coding allows us to invoke for example the double-throughput 16-level quadrature amplitude modulation (16-QAM) mode instead of the standard convolutional-coded 4-QAM mode. This facilitates doubling the bit rate and hence improving the video quality     

A variable bit rate video codec for asynchronous transfer modenetworks

The bandwidth flexibility offered by the asynchronous transfer mode (ATM) technique makes it possible to select picture quality and bandwidth over a wide range in a simple and straightforward manner. A prototype model of a video codec was developed that demonstrates the feasibility of both variable bit rate (VBR) coding and user-selectable picture quality. The VBR coding algorithm is discussed and it is shown how a stabilized quality is achieved and how this quality and associated bandwidth can be selected by the user. How error propagation is limited to reduce the visibility of cell losses is also discussed. Interfaces with the ATM network are analyzed, with emphasis on decoder synchronization and absorption of cell delay jitter. The VBR codec offers very good picture quality for videophony applications at an equivalent load of 5.9 Mb/s. Picture quality remains relatively constant, even for heavy motion     

Rate-distortion driven decoder-side bitplane mode decision for distributed video coding

Distributed video coding (DVC) features simple encoders but complex decoders, which lies in contrast to conventional video compression solutions such as H.264/AVC. This shift in complexity is realized by performing motion estimation at the decoder side instead of at the encoder, which brings a number of problems that need to be dealt with. One of these problems is that, while employing different coding modes yields significant coding gains in classical video compression systems, it is still difficult to fully exploit this in DVC without increasing the complexity at the encoder side. Therefore, in this paper, instead of using an encoder-side approach, techniques for decoder-side mode decision are proposed. A rate-distortion model is derived that takes into account the position of the side information in the quantization bin. This model is then used to perform mode decision at the coefficient level and bitplane level. Average rate gains of 13–28% over the state-of-the-art DISCOVER codec are reported, for a GOP of size four, for several test sequences.     

Iterative wyner-ziv decoding for unidirectional distributed video coding

Unidirectional distributed video coding (DVC) is one of the untouched areas of DVC, which has to be necessarily employed when the feedback channel is not available. Thus, to serve that purpose, proposed is a unidirectional distributed video coding using a parallel Wyner-Ziv architecture. Simulation results show that up to 6.5 dB PSNR gain can be obtained with the proposed codec over the conventional DVC codec with no feedback channel at the same bit rate and the computational cost     

CDV-DVC: Transform-domain distributed video coding with multiple channel division

This paper proposes an efficient distributed coding system based on multiple channel division. We develop the hierarchical motion refinement scheme using DC syndrome bits to generate high quality side information (SI) for Wyner–Ziv (WZ) frames. Moreover, we estimate local distortion characteristics of an SI frame and encode the SI frame in three coding modes: skip mode for the reliable channel, WZ mode for the medium channel, and intra mode for the unreliable channel. No bit is transmitted in the skip mode. Syndrome bits in the WZ mode are adaptively allocated based on the local distortion characteristics. The H.264 intra coding is performed in the intra mode to recover severely erroneous blocks. Experimental results show that the proposed algorithm provides significantly better rate-distortion performance than the state-of-the-art DISCOVER codec.     

Nonlinear quantisation for pixel domain distributed video coding

A nonlinear quantisation algorithm for pixel domain distributed video codec (DVC) is proposed. A residual signal is generated at the encoder considering the Wyner-Ziv frame to be encoded and adjacent reference frames and this residual signal is quantised using a nonlinear quantiser. The proposed algorithm is simulated for a number of test video sequences and the results depict a significant improvement of rate distortion performance, by reducing the bit rate while keeping the same PSNR when compared with available pixel domain DVC codec that uses a linear quantiser.     

Cell-loss concealment techniques for layered video codecs in an ATMnetwork

A layered video coding scheme with its inherent cell loss resilience has been considered as a means for transporting reliably integrated video services over an asynchronous transfer mode (ATM) based network such as the broadband-ISDN. This paper presents some data concealment techniques that can be implemented in the coding of video data at the encoder, in the ATM adaptation layer (AAL) functionality of network realization and at the decoder to improve the performance of a layered codec under different conditions of video packet loss. The performance of these techniques are verified by software simulations.     

Fast block mode decision algorithm in H.264/AVC video coding

The recent video coding standard H.264/AVC show extremely higher coding efficiency compare to any other previous standards. H.264/AVC can achieve over 50% of bit rate saving with same quality using the rate–distortion process, but it brings high computational complexity. In this paper, we propose an algorithm that can reduce the complexity of the codec by reducing the block mode decision process adaptively. Block mode decision process in H.264/AVC consists of inter mode decision process and intra mode decision process. We deal with reduction method for inter and intra mode decision. In this paper an efficient method is proposed to reduce the inter mode decision complexity using the direct prediction methods based on block correlation and adaptive rate distortion cost threshold for early stopping. The fast intra mode reduction algorithm based on inter mode information is also proposed to reduce the computational complexity. The experimental results show that the proposed algorithm can achieve up to 63.34–77.39% speed up ratio with a little PSNR loss. Increment in bit requirement is also not much noticeable.     

A fully scalable motion model for scalable video coding.

Motion information scalability is an important requirement for a fully scalable video codec, especially for decoding scenarios of low bit rate or small image size. So far, several scalable coding techniques on motion information have been proposed, including progressive motion vector precision coding and motion vector field layered coding. However, it is still vague on the required functionalities of motion scalability and how it collaborates flawlessly with other scalabilities, such as spatial, temporal, and quality, in a scalable video codec. In this paper, we first define the functionalities required for motion scalability. Based on these requirements, a fully scalable motion model is proposed along with tailored encoding techniques to minimize the coding overhead of scalability. Moreover, the associated rate distortion optimized motion estimation algorithm will be provided to achieve better efficiency throughout various decoding scenarios. Simulation results will be presented to verify the superiorities of proposed scalable motion model over nonscalable ones.     

Highly scalable wavelet-based video codec for very low bit-rateenvironment

We introduce a highly scalable video compression system for very low bit-rate videoconferencing and telephony applications around 10-30 kbits/s. The video codec first performs a motion-compensated three-dimensional (3-D) wavelet (packet) decomposition of a group of video frames, and then encodes the important wavelet coefficients using a new data structure called tri-zerotrees (TRI-ZTR). Together, the proposed video coding framework forms an extension of the original zero tree idea of Shapiro (1992) for still image compression. In addition, we also incorporate a high degree of video scalability into the codec by combining the layered/progressive coding strategy with the concept of embedded resolution block coding. With scalable algorithms, only one original compressed video bit stream is generated. Different subsets of the bit stream can then be selected at the decoder to support a multitude of display specifications such as bit rate, quality level, spatial resolution, frame rate, decoding hardware complexity, and end-to-end coding delay. The proposed video codec also allows precise bit rate control at both the encoder and decoder, and this can be achieved independently of the other video scaling parameters. Such a scheme is very useful for both constant and variable bit rate transmission over mobile communication channels, as well as video distribution over heterogeneous multicast networks. Finally, our simulations demonstrated comparable objective and subjective performance when compared to the ITU-T H.263 video coding standard, while providing both multirate and multiresolution video scalability     

The performance of layered video over an IP network

We evaluate the quality of full-motion video, when transmitted over IP via a two-layer codec and CBQ routers in the presence of TCP traffic. We investigate the effects of packet size and distribution of I-frames. We derive guidelines for the cost-effective divisions of bandwidth between base and enhancement layers, so as to maintain perceived quality in the presence of known amounts of packet loss.     

Absolute value coding for robust and scalable video coding

Absolute value coding is introduced as a method for significantly reducing temporal drift within a motion compensated predictive video codec in the presence of loss. Drift reduction both improves error resilience and enables scalability by omission of parts of the bit-stream. In conjunction with matching pursuits, the system can be used to provide a displaced frame difference codec using fixed length codewords, which further improves error resilience and facilitates simple bit-stream editing.     

The impact of the ATM concept on video coding

The induction of the asynchronous transfer mode (ATM) concept may significantly influence the coding of video services for broadband networks. The authors show how the absence of a physical channel structure and the ability to switch bursty traffic can be used to enhance video coding. Packetization defects and their impact on picture quality, coding algorithms, and synchronization schemes are studied. The authors describe variable-bit-rate coding and report on the results obtained with a hardware implementation of a variable-bit-rate video codec. Statistical multiplexing gain figures are given. The influence of cell loss on image quality is discussed and simulation results are given. A layered coding model offering good cell loss concealment properties and high flexibility is described     

Reconfigurable video coding on multicore

The current monolithic and lengthy scheme behind the standardization and the design of new video coding standards is becoming inappropriate to satisfy the dynamism and changing needs of the video coding community. Such scheme and specification formalism does not allow the clear commonalities between the different codecs to be shown, at the level of the specification nor at the level of the implementation. Such a problem is one of the main reasons for the typically long interval elapsing between the time a new idea is validated until it is implemented in consumer products as part of a worldwide standard. The analysis of this problem originated a new standard initiative within the International Organization for Standardization (ISO)/International Electrotechnical Commission (IEC) Moving Pictures Experts Group (MPEG) committee, namely Reconfigurable Video Coding (RVC). The main idea is to develop a video coding standard that overcomes many shortcomings of the current standardization and specification process by updating and progressively incrementing a modular library of components. As the name implies, flexibility and reconfigurability are new attractive features of the RVC standard. Besides allowing for the definition of new codec algorithms, such features, as well as the dataflow-based specification formalism, open the way to define video coding standards that expressly target implementations on platforms with multiple cores. This article provides an overview of the main objectives of the new RVC standard, with an emphasis on the features that enable efficient implementation on platforms with multiple cores. A brief introduction to the methodologies that efficiently map RVC codec specifications to multicore platforms is accompanied with an example of the possible breakthroughs that are expected to occur in the design and deployment of multimedia services on multicore platforms.     

基于TD-SCDMA的ARM9无线视频监控系统设计

本文设计了一个基于TQ2440开发板的无线视频监控系统,前端视频采集编码系统以嵌入式Linux操作系统为平台,运用MPEG-4编解码;传输系统采用中国移动的TD-SCDMA无线网络,无线传输模块采用重邮信科公司的基于TD-SCDMA的TD230A;后端监控系统采用客户机/服务器模式,监控软件采用Socket编程。本文阐述了整个系统的软硬件功能与组成,真正实现了视频监控的无线化,满足无线视频监控系统的要求。     

Efficient video coding with fractional resolution sprite prediction technique

An efficient algorithm for dynamic sprite-based video coding with fractional resolution motion compensations is presented. Different from the traditional sprite coding, the global motion and local motion are jointly compensated at two stages. The new techniques, developed in a JVT codec, are also utilised. Experimental results demonstrate that the proposed algorithm can averagely save 8% bit rate compared to JVT codec for the typical test sequences.