Complexity management of H.264/AVC video compression.

The H. 264/AVC video coding standard offers significantly improved compression efficiency and flexibility compared to previous standards. However, the high computational complexity of H. 264/AVC is a problem for codecs running on low-power hand held devices and general purpose computers. This thesis presents new techniques to reduce, control and manage the computational complexity of an H. 264/AVC codec. A new complexity reduction algorithm for H. 264/AVC is developed. This algorithm predicts "skipped" macroblocks prior to motion estimation by estimating a Lagrange ratedistortion cost function. Complexity savings are achieved by not processing the macroblocks that are predicted as "skipped". The Lagrange multiplier is adaptively modelled as a function of the quantisation parameter and video sequence statistics. Simulation results show that this algorithm achieves significant complexity savings with a negligible loss in rate-distortion performance. The complexity reduction algorithm is further developed to achieve complexity-scalable control of the encoding process. The Lagrangian cost estimation is extended to incorporate computational complexity. A target level of complexity is maintained by using a feedback algorithm to update the Lagrange multiplier associated with complexity. Results indicate that scalable complexity control of the encoding process can be achieved whilst maintaining near optimal complexity-rate-distortion performance. A complexity management framework is proposed for maximising the perceptual quality of coded video in a real-time processing-power constrained environment. A real-time frame-level control algorithm and a per-frame complexity control algorithm are combined in order to manage the encoding process such that a high frame rate is maintained without significantly losing frame quality. Subjective evaluations show that the managed complexity approach results in higher perceptual quality compared to a reference encoder that drops frames in computationally constrained situations. These novel algorithms are likely to be useful in implementing real-time H. 264/AVC standard encoders in computationally constrained environments such as low-power mobile devices and general purpose computers

Low-complexity motion estimation for the Scalable Video Coding extension of H.264/AVC

The recently standardized Scalable Video Coding(SVC) extension of H.264/AVC allows bitstream scalability with improved rate-distortion efficiency with respect to the classical Simulcasting approach, at the cost of an increased computational complexity of the encoding process. So one critical issue related to practical deployment of SVC is the complexity reduction, fundamental to use it in consumer applications. In this paper, we present a fully scalable fast motion estimation algorithm that enables an excellent complexity performance

Multilayers Fast Mode Decision Algorithms for Scalable Video Coding

Abstract: Scalable video coding (SVC) is the extension of H.264/AVC standard. The features in SVC are also developed from the H.264/AVC standard, so that SVC has more features compared to H.264/AVC standard. This provides higher coding complexity in SVC encoder which causes higher encoding time for SVC. SVC is gaining great interest because of its ability and scalability to adapt in various network conditions. SVC allows partial transmission and decoding of a bitstream. This research deals with multilayers fast mode decision algorithm for decreasing encoding time or fastening the mode decision process of the SVC encoder. The proposed fast mode decision scheme has been implemented and is successfully decrease encoding time with negligible loss of quality and bitrate requirement. The simulation result shows the proposed fast mode decision algorithm provides time saving up to 45 % while maintaining video quality with negligible PSNR loss

Complexity scalable motion estimation control for H.264/AVC

Guaranteeing real-time performance for video encoding on platforms with limited resources is becoming increasingly important for consumer electronics applications. In this paper, an extension of an H.264/AVC encoder with complexity scalable motion estimation (ME) control is presented. An upper bound on the complexity of encoding a single frame is achieved by restricting Sum of Absolute Differences (SAD) computations performed during ME and trading complexity allocation per frame for output quality. Allocation based on residual, i.e. SAD distortion of the final ME match before quantization, of the co-located macroblock in the previous frame outperforms other approaches in the literature in video quality

Multilayers fast mode decision algorithm for scalable video coding: design, implementation, and streaming evaluation on IEEE 802.11g wireless LAN

Nowadays the advancement of technologies has reached the massive growth and commercial success in multimedia and mobile communication. The advancement and development in video coding technology, together with the increase of storage capacity network infrastructures and computing power are enabling an increasing number of video applications. Scalable video coding (SVC) is the extension of H.264/AVC standard. The features in SVC are also developed from the H.264/AVC standard, so that SVC has more features compared to H.264/AVC standard. This provides higher coding complexity in SVC encoder which causes higher encoding time for SVC. SVC is gaining great interest because of its ability and scalability to adapt in various network conditions. SVC allows partial transmission and decoding of a bitstream. This research deals with fast mode decision algorithm for decreasing encoding time or fastening the mode decision process of the SVC encoder. Moreover, the performance of SVC over wireless network will be evaluated. The simulation tools can be of great help for a better understanding of the streaming analysis over the network. Hence, this research utilizes Scalable Video Evaluation Framework (SVEF). The fast mode decision scheme has been implemented and successfully decreased encoding time with negligible loss of quality and bitrate requirement. The streaming simulation has also been performed using the SVEF simulator. The simulation result shows the proposed fast mode decision algorithm provides time saving up to 45 % while maintaining video quality with negligible PSNR loss. For the streaming video, the received packets on the receiver can be reconstructed on maintained video quality with also negligible PSNR loss

Temporal video transcoding from H.264/AVC-to-SVC for digital TV broadcasting

Mobile digital TV environments demand flexible video compression like scalable video coding (SVC) because of varying bandwidths and devices. Since existing infrastructures highly rely on H.264/AVC video compression, network providers could adapt the current H.264/AVC encoded video to SVC. This adaptation needs to be done efficiently to reduce processing power and operational cost. This paper proposes two techniques to convert an H.264/AVC bitstream in Baseline (P-pictures based) and Main Profile (B-pictures based) without scalability to a scalable bitstream with temporal scalability as part of a framework for low-complexity video adaptation for digital TV broadcasting. Our approaches are based on accelerating the interprediction, focusing on reducing the coding complexity of mode decision and motion estimation tasks of the encoder stage by using information available after the H. 264/AVC decoding stage. The results show that when our techniques are applied, the complexity is reduced by 98 % while maintaining coding efficiency

Video adaptation for mobile digital television

Mobile digital television is one of the new services introduced recently by telecommunications operators in the market. Due to the possibilities of personalization and interaction provided, together with the increasing demand of this type of portable services, it would be expected to be a successful technology in near future. Video contents stored and transmitted over the networks deployed to provide mobile digital television need to be compressed to reduce the resources required. The compression scheme chosen by the great majority of these networks is H.264/AVC. Compressed video bitstreams have to be adapted to heterogeneous networks and a wide range of terminals. To deal with this problem scalable video coding schemes were proposed and standardized providing temporal, spatial and quality scalability using layers within the encoded bitstream. Because existing H.264/AVC contents cannot benefit from scalability tools, efficient techniques for migration of single-layer to scalable contents are desirable for supporting these mobile digital television systems. This paper proposes a technique to convert from single-layer H.264/AVC bitstream to a scalable bitstream with temporal scalability. Applying this approach, a reduction of 60% of coding complexity is achieved while maintaining the coding efficiency

Scalable video transcoding for mobile communications

Mobile multimedia contents have been introduced in the market and their demand is growing every day due to the increasing number of mobile devices and the possibility to watch them at any moment in any place. These multimedia contents are delivered over different networks that are visualized in mobile terminals with heterogeneous characteristics. To ensure a continuous high quality it is desirable that this multimedia content can be adapted on-the-fly to the transmission constraints and the characteristics of the mobile devices. In general, video contents are compressed to save storage capacity and to reduce the bandwidth required for its transmission. Therefore, if these compressed video streams were compressed using scalable video coding schemes, they would be able to adapt to those heterogeneous networks and a wide range of terminals. Since the majority of the multimedia contents are compressed using H.264/AVC, they cannot benefit from that scalability. This paper proposes a technique to convert an H.264/AVC bitstream without scalability to a scalable bitstream with temporal scalability as part of a scalable video transcoder for mobile communications. The results show that when our technique is applied, the complexity is reduced by 98 % while maintaining coding efficiency