An efficient rate control algorithm for a wavelet video codec

Rate control plays an essential role in video coding and transmission to provide the best video quality at the receiver's end given the constraint of certain network conditions. In this paper, a rate control algorithm using the Quality Factor (QF) optimization method is proposed for the wavelet-based video codec and implemented on an open source Dirac video encoder. A mathematical model which we call Rate-QF (R - QF) model is derived to generate the optimum QF for the current coding frame according to the target bitrate. The proposed algorithm is a complete one pass process and does not require complex mathematical calculation. The process of calculating the QF is quite simple and further calculation is not required for each coded frame. The experimental results show that the proposed algorithm can control the bitrate precisely (within 1% of target bitrate in average). Moreover, the variation of bitrate over each Group of Pictures (GOPs) is lower than that of H.264. This is an advantage in preventing the buffer overflow and underflow for real-time multimedia data streaming

Comparative analysis of DIRAC PRO-VC-2, H.264 AVC and AVS CHINA-P7

Video codec compresses the input video source to reduce storage and transmission bandwidth requirements while maintaining the quality. It is an essential technology for applications, to name a few such as digital television, DVD-Video, mobile TV, videoconferencing and internet video streaming. There are different video codecs used in the industry today and understanding their operation to target certain video applications is the key to optimization. The latest advanced video codec standards have become of great importance in multimedia industries which provide cost-effective encoding and decoding of video and contribute for high compression and efficiency. Currently, H.264 AVC, AVS, and DIRAC are used in the industry to compress video. H.264 codec standard developed by the ITU-T Video Coding Experts Group (VCEG) together with the ISO/IEC Moving Picture Experts Group (MPEG). Audio-video coding standard (AVS) is a working group of audio and video coding standard in China. VC-2, also known as Dirac Pro developed by BBC, is a royalty free technology that anyone can use and has been standardized through the SMPTE as VC-2. H.264 AVC, Dirac Pro, Dirac and AVS-P2 are dedicated to High Definition Video, while AVS-P7 is to mobile video. Out of many standards, this work performs a comparative analysis for the H.264 AVC, DIRAC PRO/SMPTE-VC-2 and AVS-P7 standards in low bitrate region and high bitrate region. Bitrate control and constant QP are the methods which are employed for analysis. Evaluation parameters like Compression Ratio, PSNR and SSIM are used for quality comparison. Depending on target application and available bitrate, order of performance is mentioned to show the preferred codec

An efficient rate control algorithm for a wavelet video codec

Rate control plays an essential role in video coding and transmission to provide the best video quality at the receiver's end given the constraint of certain network conditions. In this paper, a rate control algorithm using the Quality Factor (QF) optimization method is proposed for the wavelet-based video codec and implemented on an open source Dirac video encoder. A mathematical model which we call Rate-QF (R - QF) model is derived to generate the optimum QF for the current coding frame according to the target bitrate. The proposed algorithm is a complete one pass process and does not require complex mathematical calculation. The process of calculating the QF is quite simple and further calculation is not required for each coded frame. The experimental results show that the proposed algorithm can control the bitrate precisely (within 1% of target bitrate in average). Moreover, the variation of bitrate over each Group of Pictures (GOPs) is lower than that of H.264. This is an advantage in preventing the buffer overflow and underflow for real-time multimedia data streaming

Influence of Chroma Subsampling on Objective Video Quality Assessment for High Resolutions

This paper deals with the influence of chroma subsampling on video quality measured by objective metrics for H.264/AVC and H.265/HEVC compression standards. The evaluation is done for eight types of sequences with full HD and ultra HD resolutions depending on content. The experimental results showed that there is no impact of chroma subsampling on the video. According to the results, it can also be said that H.265/HEVC codec yields better compression efficiency than H.264/AVC and the different is more visible in UHD resolution. The bigger difference in quality is in lower bitrates, with increasing bitrate the quality of H.264/AVC codec approaches the H.265/HEVC codec

Video coding standards

Review by Ashraf A. Kassim, Professor, Department of Electrical & Computer Engineering, and Associate Dean, School of Engineering, National University of Singapore.     The book consists of eight chapters of which the first two provide an overview of various video & image coding standards, and video formats. The next four chapters present in detail the Audio & video standard (AVS) of China, the H.264/MPEG-4 Advanced video coding (AVC) standard, High efficiency video coding (HEVC) standard and the VP6 video coding standard (now VP10) respectively. The performance of the wavelet based Dirac video codec is compared with H.264/MPEG-4 AVC in chapter 7. Finally in chapter 8, the VC-1 video coding standard is presented together with VC-2 which is based on the intra frame coding of Dirac and an outline of a H.264/AVC to VC-1 transcoder.   The authors also present and discuss relevant research literature such as those which document improved methods & techniques, and also point to other related resources including standards documents, open source software, review papers, and keynote speeches. The numerous projects presented in the later chapters are particularly thought provoking and challenging. These would be useful for readers, especially graduate students, helping them develop a deeper understanding of the standards and also direct them to further research. True to its name, “Video Coding Standards” would serve as a unique resource for researchers, developers and graduate students in the video coding field, enabling them to achieve a good understanding of these current standards including the differences in performance and limitations, as well as keep abreast of latest developments

Influence of Bit Depth on Objective Video Quality Assessment for High Resolutions

This paper deals with the influence of bit depth on the objective quality assessment. All tests were conducted on eight video sequences, while each one has different spatial and temporal information; 8-bit and 10-bit bit depths were used; analysed videos were in full and ultra HD resolutions, and coding efficiency of H.264 and H.265 was compared. The metrics PSNR and SSIM for evaluation of objective video quality were used

Research and developments of Dirac video codec

This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University.In digital video compression, apart from storage, successful transmission of the compressed video data over the bandwidth limited erroneous channels is another important issue. To enable a video codec for broadcasting application, it is required to implement the corresponding coding tools (e.g. error-resilient coding, rate control etc.). They are normally non-normative parts of a video codec and hence their specifications are not defined in the standard. In Dirac as well, the original codec is optimized for storage purpose only and so, several non-normative part of the encoding tools are still required in order to be able to use in other types of application. Being the "Research and Developments of the Dirac Video Codec" as the research title, phase I of the project is mainly focused on the error-resilient transmission over a noisy channel. The error-resilient coding method used here is a simple and low complex coding scheme which provides the error-resilient transmission of the compressed video bitstream of Dirac video encoder over the packet erasure wired network. The scheme combines source and channel coding approach where error-resilient source coding is achieved by data partitioning in the wavelet transformed domain and channel coding is achieved through the application of either Rate-Compatible Punctured Convolutional (RCPC) Code or Turbo Code (TC) using un-equal error protection between header plus MV and data. The scheme is designed mainly for the packet-erasure channel, i.e. targeted for the Internet broadcasting application. But, for a bandwidth limited channel, it is still required to limit the amount of bits generated from the encoder depending on the available bandwidth in addition to the error-resilient coding. So, in the 2nd phase of the project, a rate control algorithm is presented. The algorithm is based upon the Quality Factor (QF) optimization method where QF of the encoded video is adaptively changing in order to achieve average bitrate which is constant over each Group of Picture (GOP). A relation between the bitrate, R and the QF, which is called Rate-QF (R-QF) model is derived in order to estimate the optimum QF of the current encoding frame for a given target bitrate, R. In some applications like video conferencing, real-time encoding and decoding with minimum delay is crucial, but, the ability to do real-time encoding/decoding is largely determined by the complexity of the encoder/decoder. As we all know that motion estimation process inside the encoder is the most time consuming stage. So, reducing the complexity of the motion estimation stage will certainly give one step closer to the real-time application. So, as a partial contribution toward realtime application, in the final phase of the research, a fast Motion Estimation (ME) strategy is designed and implemented. It is the combination of modified adaptive search plus semi-hierarchical way of motion estimation. The same strategy was implemented in both Dirac and H.264 in order to investigate its performance on different codecs. Together with this fast ME strategy, a method which is called partial cost function calculation in order to further reduce down the computational load of the cost function calculation was presented. The calculation is based upon the pre-defined set of patterns which were chosen in such a way that they have as much maximum coverage as possible over the whole block. In summary, this research work has contributed to the error-resilient transmission of compressed bitstreams of Dirac video encoder over a bandwidth limited error prone channel. In addition to this, the final phase of the research has partially contributed toward the real-time application of the Dirac video codec by implementing a fast motion estimation strategy together with partial cost function calculation idea.BBC R&D and Brunel University

EXPERIMENTS ON VIDEO STREAMING OVER COMPUTER NETWORKS

Video traffic (including streaming video service) is dominating the Internet traffic today. Video can be streamed using a dedicated server, a content delivery network (CDN), or peer-to-peer (P2P) overlays across a network. Video can be transmitted in multiple formats and at different resolutions. Video is also being distributed to a variety of devices (fixed and mobile)