One-pass Bitrate Control for MPEG-4 Scalable Video Coding using rho-domain

International audienceThis paper presents an attractive rate control scheme for the new MPEG-4 Scalable Video Coding standard. Our scheme enables us to control the bitrate at the output of the encoder on each video layer with great accuracy. Each frame is encoded only once, so that the computational complexity of the whole scheme is very low. The three spatial, temporal and quality scalabilities are handled correctly, as well as inter layer prediction and hierarchical B frames. A linear bitrate model is used to predict the output bitrate for a frame, based on a simple and effective framework called rho-domain. A coding-complexity measure is also introduced to dispatch the available bits among the frames, in order to reach a constant quality throughout the encoded video stream. To attest the performances of our rate control scheme, we present comprehensive results on some representative scalable video set-ups

Rho-domain based Rate Control Scheme for Spatial, Temporal and Quality Scalable Video Coding

International audienceRate control is a capital issue in video coding. It allows a regulation of the bitrate out from the encoder, to cope with some network transmission or quality constraints. Scalable Video Coding emerged several years ago as an answer to the growing need of application-adaptable video streams. Although the interest of scalable video coding has been confirmed by recent studies, it can not be used in practical contexts without proper rate control techniques. In this paper we present a new rate control scheme for scalable video, based on a simple yet attractive bitrate modelling framework called -domain. Our scheme performs accurate rate control on spatial, temporal and quality scalabilities, while maintaining a constant PSNR. Inter layer prediction is also handled effectively

Slight-Delay Shaped Variable Bit Rate (SD-SVBR) Technique for Video Transmission

The aim of this thesis is to present a new shaped Variable Bit Rate (VBR) for video transmission, which plays a crucial role in delivering video traffic over the Internet. This is due to the surge of video media applications over the Internet and the video typically has the characteristic of a highly bursty traffic, which leads to the Internet bandwidth fluctuation. This new shaped algorithm, referred to as Slight Delay - Shaped Variable Bit Rate (SD-SVBR), is aimed at controlling the video rate for video application transmission. It is designed based on the Shaped VBR (SVBR) algorithm and was implemented in the Network Simulator 2 (ns-2). SVBR algorithm is devised for real-time video applications and it has several limitations and weaknesses due to its embedded estimation or prediction processes. SVBR faces several problems, such as the occurrence of unwanted sharp decrease in data rate, buffer overflow, the existence of a low data rate, and the generation of a cyclical negative fluctuation. The new algorithm is capable of producing a high data rate and at the same time a better quantization parameter (QP) stability video sequence. In addition, the data rate is shaped efficiently to prevent unwanted sharp increment or decrement, and to avoid buffer overflow. To achieve the aim, SD-SVBR has three strategies, which are processing the next Group of Picture (GoP) video sequence and obtaining the QP-to-data rate list, dimensioning the data rate to a higher utilization of the leaky-bucket, and implementing a QP smoothing method by carefully measuring the effects of following the previous QP value. However, this algorithm has to be combined with a network feedback algorithm to produce a better overall video rate control. A combination of several video clips, which consisted of a varied video rate, has been used for the purpose of evaluating SD-SVBR performance. The results showed that SD-SVBR gains an impressive overall Peak Signal-to-Noise Ratio (PSNR) value. In addition, in almost all cases, it gains a high video rate but without buffer overflow, utilizes the buffer well, and interestingly, it is still able to obtain smoother QP fluctuation

Rate distortion control in digital video coding

Lossy compression is widely applied for coding visual information in applications such as entertainment in order to achieve a high compression ratio. In this case, the video quality worsens as the compression ratio increases. Rate control tries to use the bit budget properly so the visual distortion is minimized. Rate control for H.264, the state-of-the-art hybrid video coder, is investigated. Based on the Rate-Distortion (R-D) slope analysis, an operational rate distortion optimization scheme for H.264 using Lagrangian multiplier method is proposed. The scheme tries to find the best path of quantization parameter (OP) options at each macroblock. The proposed scheme provides a smoother rate control that is able to cover a wider range of bit rates and for many sequences it outperforms the H.264 (JM92 version) rate control scheme in the sense of PSNR. The Bath University Matching Pursuit (BUMP) project develops a new matching pursuit (MP) technique as an alternative to transform video coders. By combining MP with precision limited quantization (PLO) and multi-pass embedded residual group encoder (MERGE), a very efficient coder is built that is able to produce an embedded bit stream, which is highly desirable for rate control. The problem of optimal bit allocation with a BUMP based video coder is investigated. An ad hoc scheme of simply limiting the maximum atom number shows an obvious performance improvement, which indicates a potential of efficiency improvement. An in depth study on the bit Rate-Atom character has been carried out and a rate estimation model has been proposed. The model gives a theoretical description of how the oit number changes. An adaptive rate estimation algorithm has been proposed. Experiments show that the algorithm provides extremely high estimation accuracy. The proposed R-D source model is then applied to bit allocation in the BUMP based video coder. An R-D slope unifying scheme was applied to optimize the performance of the coder'. It adopts the R-D model and fits well within the BUMP coder. The optimization can be performed in a straightforward way. Experiments show that the proposed method greatly improved performance of BUMP video coder, and outperforms H.264 in low and medium bit rates by up to 2 dB.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Rate-adaptive H.264 for TCP/IP networks

While there has always been a tremendous demand for streaming video over TCP/IP networks, the nature of the application still presents some challenging issues. These applications that transmit multimedia data over best-effort networks like the Internet must cope with the changing network behavior; specifically, the source encoder rate should be controlled based on feedback from a channel estimator that probes the network periodically. First, one such Multimedia Streaming TCP-Friendly Protocol (MSTFP) is considered, which iteratively integrates forward estimation of network status with feedback control to closely track the varying network characteristics. Second, a network-adaptive embedded bit stream is generated using a r-domain rate controller. The conceptual elegance of this r-domain framework stems from the fact that the coding bit rate ) (R is approximately linear in the percentage of zeros among the quantized spatial transform coefficients ) ( r , as opposed to the more traditional, complex and highly nonlinear ) ( Q R characterization. Though the r-model has been successfully implemented on a few other video codecs, its application to the emerging video coding standard H.264 is considered. The extensive experimental results show thatrobust rate control, similar or improved Peak Signal to Noise Ratio (PSNR), and a faster implementation