HDTV CODEC for Digital Recording

A new hybrid coding technique is introduced which is based on the Discrete Cosine Transform, interframe DPCM, conditional replenishment, detection of significant subareas in the transform domain, adaptive quantization, adaptive Huffman coding and postbuffer control. This coder concept is the result of a comparison of several coding methods including uniform/nonuniform quantization, constant/variable word length coding and prebuffer/post-buffer control schemes. An important feature of the presented coder is the selection of transform coefficients within each block which are grouped in subareas for adaptive entropy coding. The components of the coder are described and its excellent performance is demonstrated by means of SNR-measurements and a typical videoconference sequence.

In recent years, video data have increased in size, which results in enormous transmission pressure. Rate control plays an important role in stabilizing video stream transmissions by balancing the rate and distortion of video compression. To achieve high-quality videos through low-bandwidth transmission, video multi-scale-based end-to-end rate control is proposed. First, to reduce video data, the original video is processed using multi-scale bicubic downsampling as the input. Then, the end-to-end rate control model is implemented. By fully using the temporal coding correlation, a two-branch residual-based network and a two-branch regression-based network are designed to obtain the optimal bit rate ratio and Lagrange multiplier λ for rate control. For restoring high-resolution videos, a hybrid efficient distillation SISR network (HEDS-Net) is designed to build low-resolution and high-resolution feature dependencies, in which a multi-branch distillation network, a lightweight attention LCA block, and an upsampling network are used to transmit deep extracted frame features, enhance feature expression, and improve image detail restoration abilities, respectively. The experimental results show that the PSNR and SSIM BD rates of the proposed multi-scale-based end-to-end rate control are −1.24% and −0.50%, respectively, with 1.82% rate control accuracy.

It has been shown that the quality of multimedia video and the need of real time video transmission become widely increased in these days and high efficiency video coding (HEVC) becomes the newest standard. Based on the theory of ratedistortion coding, the R-X model can describe the rate-distortion relationship more accurately in comparison with the existing traditional R-Q model. With the development of screen content coding, this paper proposes a new adaptive intra frame complexity measure method based on two complexity measure methods with a relative coefficient for intra bit rate control, respectively are the gradient based complexity measure and edge based complexity measure. Then the paper proposes an improved rate control method for the intra-frame rate control, which merges the adaptive intra frame complexity measure with R-X model based on HEVC. Along with this new adaptive rate control approach, it will show improved accuracy in rate control and enhanced performance in video coding which means better video quality. The proposed scheme can reduce the frame bit mismatch ratio by 2.8175% on average and the better B-D Rate which is 0.94% on average. Experimental results verify the effectiveness of the proposed intra frame complexity method based on X-domain rate control algorithm.

The characteristics of super-high-definition images with resolutions of up to 4096*2880 pixels are examined by autocorrelation measurement, and these values are compared with an image having spatial resolution comparable to existing TV. In order to obtain the basic characteristics of such images and coding performance, a simulation system including a digital camera with 4096*4096 pixels and a frame memory and monitor system with 2048*2048 pixels is set up. Two different DCT (discrete cosine transform) coding schemes, DCT with adaptive bit allocation and DCT with variable-length coding, are applied to evaluate the performance of transform coding on super-high-definition images. >

At recently, the most of the digital images are stored and transferred in their compressed format using discrete cosine transform (DCT)-based compression technique. DCT is one of the most important data compression technique due to the efforts from Joint Photographic Experts Group(JPEG). Blind steganalysis means how to detect the presence of the messages that are hidden using different types of steganography algorithms and has the ability to detect new unknown steganography algorithms. This paper presents blind steganalysis technique that can reliably detect the existence of messages hidden in JPEG files. In order to save the computation and memory cost, it is desirable to have image processing operations implemented directly in the DCT domain. The proposed method is based on extracting features directly from DCT domain through the analysis of differences between DCT coefficients before and after cropping. The extracted features are prepared as input to Support Vector Machine (SVM) to classify the image as stego (image that contain secret message) or clean (image that does not contain secret message). The experiments performed show that the proposed method yields better classification accuracy compared with other related works.

Joint source-channel decoding of variable length codes (VLC) for image and video streaming transmission over unreliable links, such as wireless networks, is a subject of increasing interest. Much more residual source redundancy can be exploited when both types of correlation: (i) the correlation between bits inside a VLC codeword as well as; (ii) the correlation between VLC codewords of a VLC sequence unit (e.g. corresponding to one image block), are taken into account. The paper (Hang Nguyen et al, IEEE Int. Conf. on Acoustics, Speech, and Sigpro., 2004) proposes an optimum maximum likelihood (ML) decoder of VLC sequences which can exploit these two kinds of correlation and outperforms the existing VLC decoders. This paper proposes a reduced complexity version of this optimal VLC decoder. Simulation results show that the complexity is reduced by 5 in terms of number of possible candidates, while the performance is only slightly sub-optimal compared with the optimal version of the Hang Nguyen paper.

Rate control plays an important role in video coding and streaming applications with bandwidth constraints. While most researches are proposed to improve the coding efficiency’ the fluctuation of video quality is seldom considered. Many rate control schemes suffer from unreliable initialization of coding parameters, which leads to seriously inconsistent quality at the beginning of a video. Besides, the hierarchical structure for frame references introduces more quality fluctuations, although it improves the coding efficiency significantly. This paper presents a two pass rate control method that aims for a consistent visual quality. The video is downsampled by four times, and then encoded for the first pass. A fixed Lagrange multiplier $(\lambda)$ is derived from the information recorded in the first pass, and then applied for all frames in the second coding pass. A QP adjustment policy is adopted to maintain a consistent quality and a constant bitrate. Experimental results show that the proposed rate control method can reduce the fluctuation of video quality to be averagely 94.63% less than that encoded by the HEVC Test Model (HM16.9).

Rate control has been regarded as an indispensable video coding tool for virtually any application involving video transmission. With the advent of many flexible tools introduced in the current state-of-the-art High Efficiency Video Coding (HEVC) standard, previous Rate-Distortion (RD) models used for rate control become insufficiently accurate. To overcome this issue, a new RD model has been recently proposed based on a robust correspondence between the rate and Lagrange multiplier λ. However, existing methods based on this model tend to perform sub-optimally after the scene change. In this paper, a two-pass rate control method is proposed, targeting Ultra High Definition Television (UHDTV) applications. In the first pass, a fast encoder with a reduced set of coding tools is used to obtain the data used for rate allocation and model parameter initialisation utilised during the second pass. Multiple encoding steps required to derive this information are avoided with the proposed variable quantization parameter framework. Experimental evaluation showed that the proposed two-pass rate control method achieves on average 4.4% BD-rate loss, compared with variable bit-rate encoding. That significantly outperforms the state-of-the-art HEVC rate control method with an average BD-rate loss of 8.8%.

Rate control plays an important role in video coding and transmission. In this paper, instead of using rate- distortion (R-D) model to perform rate control as many existing methods do, a rate-quality (R-Q) model of H.264/AVC has first been proposed to represent the coding characteristics of H.264, where PSNR (peak signal-to-noise ratio) is used to represent the reconstructed video quality. Then a H.264 rate control method at frame layer has been presented based on the proposed R-Q model. In this method, the quantization parameter (i.e. quantization step) of the current frame is determined by the proposed R-Q model according to the coding statistics of the previous coded frames. The experimental results show that, compared with the rate control algorithm of JM86 reference software, the output bit rate achieved by our proposed one is more close to the target bit rate while the reconstructed quality is comparable.

Variable length codes (VLC) have found widespread use for efficient encoding of symbols with unequal probabilities in many practical situations. However, bit errors can cause a loss of decoder synchronism that often leads to error propagation. Recent advances in the development of VLC that limit the effect of error propagation, such as reversible VLC and self-synchronising VLC, contribute further to their popularity. However, it is still important to model the performance of various VLC code sets so that comparisons can be made between different coding schemes and for different applications. Communicating sequential processes (CSP) is a well-established formal description technique that allows one to analyse the behaviour of concurrently evolving processes. It has been successfully applied to industrial-scale problems. The paper describes how CSP can be applied to the modelling of the resync process of VLC. This approach offers three main advantages. First, a complete model comprises processes and events as basic building blocks, making this approach highly scalable. Second, different semantic models provide different level of abstraction. Third, tools are available for automatic generation of sync sequences, which also provide a measure of sync performance. This facilitates comparisons of different VLC schemes in addition to code sets obtained using a given coding scheme.

Joint source and channel decoding of compressed still images

Existing power and rate control methods for wireless communication networks aim to maximize the system capacity and the network throughput, and attempt to increase the quality-of-service (QoS), but cannot guarantee the QoS. This paper presents a new power and rate control method for wireless communication networks, which is based on the priority of QoS, so the QoS can be guaranteed. A dual closed-loop power and rate controller is designed. The transmission rate is controlled by the outer loop, the target transmission rate is obtained (thus the optimal target signal-to-inference ratio (SIR) can relatively be determined) based on the priority of QoS. According to the target SIR, the transmit power is controlled by the inner loop to make the actual SIR track the target one. Simulation results show that the proposed power and rate control method has good control performance.

A novel power and rate control system model for wireless communication networks is presented, which includes uncertainties, input constraints, and time-varying delays in both state and control input. A robust delay-dependent model predictive power and rate control method is proposed, and the state feedback control law is obtained by solving an optimization problem that is derived by using linear matrix inequality (LMI) techniques. Simulation results are given to illustrate the effectiveness of the proposed method.

A real-time frame-layer rate control algorithm is proposed for low bit rate video coding over IEEE 802.11 wireless local area network (WLAN). The proposed rate control method performs bit allocation at the frame level to minimize the average distortion over an entire sequence as well as variations in distortion between frames. A new frame-layer rate-distortion model is derived, and a non-iterative optimization method is used for low computational complexity. The proposed algorithm produces low encoding time delay, and is suitable for real-time low-complexity video encoder. Experimental results indicate that the proposed control method provides better visual and PSNR performance than the existing TMN8 rate control method.

An efficient MPEG-2 to MPEG-4 video transcoder is presented in this paper. We consider the transcoding from high quality and bit rate MPEG-2 video with larger image size (e.g. 4CIF/4SIF, CIF) to lower quality and bit rate MPEG-4 video with smaller image size (e.g. CIF, QCIF). First, the transcoder needs to down-sample the input MPEG-2 video. Since the motion vectors carried by the MPEG-2 stream will be reused in the transcoding process, they are sub-sampled besides the frame pixels, and the coding mode for each down-sampled macroblock is examined. A new rate control method is proposed to convert the high bit rate MPEG-2 video to the low bit rate MPEG-4 counterpart. The proposed rate control scheme adjusts the frame rate and the frame quantization step size simultaneously according to the channel bandwidth to achieve a good temporal-spatial quality tradeoff. Due to the reuse of motion vectors, key frames (i.e. I and P frames) cannot be skipped to maintain the prediction sequential order, while some B frames containing less temporal information may be skipped in transcoding to save the bit rate. Skipped B frames can be reconstructed at the decoder to ensure the full frame rate playback. The TM7 quadratic Rate-Qtz model is adopted in the proposed rate control scheme to calculate the re-quantization step size from the given target bit. Simulations show that the proposed MPEG-2 to MPEG-4 video transcoder with rate control can out-perform the basic MPEG transcoder that adjusts the re-quantization step size at a constant frame rate. The complexity of the proposed transcoder is low so that it can be used in real-time applications.