Antonio Navarro

Fast Motion Estimation Algorithm for HEVC

Motion Estimation is an essential process in many video coding standards like MPEG-2, H.264/AVC and HEVC. Despite Motion Estimation has been used at the encoder, it is expected to be used in future consumer devices in the distributed video coding architectures. But the Motion Estimation itself consumes more than 50% coding complexity or time to encode. To reduce the computation time, many fast Motion Estimation Algorithms were proposed and implemented. The present paper proposes a new fast ME algorithm which outperforms the fast ME algorithm implemented in HEVC reference software HM.

A new packet loss model of the IEEE 802.11g wireless network for multimedia communications

A wireless indoor network model coping with packet loss and packet arrival is proposed. This novel model is compared to the well known Gilberi-Elliott (GE) model. The proposed model is shown to be more accurate than GE in a particular but very representative IEEE 802.11g scenario. The proposed model has two parameters: one is a function of the source packet rate; and the other is almost constant. The extensive usage of the GE model in data communications is due to its simplicity. Likewise, it is expected a similar adoption of our model for wireless multimedia packet communications, since it was conceived based on traffic with multimedia features.

A novel SAD architecture for variable block size motion estimation in HEVC video coding

Motion estimation (ME) is one of the critical and most time consuming tasks in video coding. The increase of block size to 64x64 and introduction of asymmetric motion partitioning (AMP) in HEVC makes variable block size motion estimation more complex and therefore requires specific hardware architecture for real time implementation. The ME process includes the calculation of SAD (Sum of Absolute Difference) of two blocks, the current and the reference blocks. The present paper proposes low complexity SAD (Sum of Absolute Difference) architecture for ME of HEVC video encoder, which is able to exploit and optimize parallelism at various levels. The proposed architecture was implemented in FPGA, and compared with other non-parallel SAD architectures. Synthesis results show that the proposed architecture takes fewer resources in FPGA when compared with results from non-parallel architectures and other contributions.

High speed SAD architectures for variable block size motion estimation in HEVC video coding

HEVC is the latest video coding standard aimed to compress double to that of its predecessor standard H.264/AVC at the cost of increased coding complexity. Motion Estimation (ME) is one of its critical tools in the encoder whose complexity drastically increases due to the increase in coding block size to 64×64 and due to the introduction of Asymmetric Motion Partitioning (AMP). Hence it requires specific hardware architectures for real time implementation. The bottleneck of ME tool is the SAD (Sum of Absolute Difference) circuit architecture which calculates SAD between current block and reference block pixels. The present paper proposes and implements three SAD architectures in FPGA. Synthesis results show that one of the proposed architectures outperforms when compared to results of other contributions, despite supporting all block modes of HEVC.

HF channel modeling for real time packet transmission

The recent rapid growth of multimedia communications has efficiently allowed delivering different services, formats and contents over an enormous variety of digital networks with IP acting as an integration protocol. The main objective of this research work is to evaluate the performance of an high frequency (HF) wireless network for transporting multimedia services according to UDP/IP protocol stack. Besides, allowing civil/amateur communications, HF bands are also used for long distance wireless military communications. Therefore, our work is based on NATO Link and Physical layer standards, STANAG 5066 and STANAG 4539, respectively. A typical transmission bandwidth is about 3 kHz resulting in a varying bit rate in the range between 75 and 12800 bps. This very low bit rate by itself imposes serious challenges for reliable real time multimedia communications. This paper discusses optimal combinations of channel coders, modulators and packet sizes in order to achieve the greatest throughput in function of the signal-to-noise ratio and HF channel conditions.

Complexity reduction methods for fast motion estimation in HEVC

Motion estimation is one of the most demanding and complex tools in block based video encoders. Variable block size motion estimation (ME) and multiple reference frames in H.264/AVC make motion estimation even more complex and time consuming. In HEVC, the complexity is even higher since there are more block sizes. This paper presents an analysis of various tools involved in some fast ME algorithms and proposes some improvements to them in order to achieve a novel fast hybrid algorithm. The proposed algorithm has been tested with HEVC reference software. Simulation results show that the algorithm achieves up to 44.7% decrease in ME complexity when compared to the fast ME algorithm (Test Zone Search or TZSearch) and up to 99% reduction in ME complexity compared to full search algorithm with negligible loss in PSNR and bitrate. Motion estimation is one of the most complex tools in block based video encoders.In HEVC, the motion estimation complexity is even higher since there are more block sizes.TZSearch algorithm is the fast motion estimation algorithm in HEVC reference software.This paper reduces the complexity of TZSearch ME algorithm upto 44.7%.The overall RD performance loss is negligible despite decrease in the complexity.

Video transcoding from H.264/AVC to MPEG-2 with reduced computational complexity

This paper addresses video transcoding from H.264/AVC into MPEG-2 with reduced complexity and high rate-distortion efficiency. While the overall concept is based on a cascaded decoder-encoder, the novel adaptation methods developed in this work have the advantage of providing very good performance in H.264/AVC to MPEG-2 transcoding. The proposed approach exploits the similarities between the coding tools used in both standards, with the objective of obtaining a computationally efficient transcoder without penalising the signal quality. Fast and efficient methods are devised for conversion of macroblock coding modes and translation of motion information in order to compute the MPEG-2 coding format with a reduced number of operations, by reusing the corresponding data embedded in the incoming H.264/AVC coded stream. In comparison with a cascaded decoder-encoder, the fast transcoder achieves computational complexity savings up to 60% with slightly better peak signal-to-noise ratio (PSNR) at the same bitrate.

SUIT-Scalable, Ultra-fast and Interoperable Interactive Television

The deployment of different types of networks makes available the contents anywhere and anytime. However, in the context of multimedia communications over heterogeneous networks, some interoperability related problems are unsolved so far. This paper discusses the advantages and disadvantages of SUIT (European IST project n. 028042), a convergent architecture between two broadband wireless networks, IEEE 802.16e (WiMAX) and DVB-T/H. The main idea is to combine in a fruitful manner DVB-T/H with the broadband wireless access network IEEE802.16e providing a low round- trip delay and robust communications at high mobile speed, above 150 km/h. In this context of network convergence, broadband networks like DVB-T/H and WiMAX will certainly play an important role, delivering multimedia data namely compressed video to fixed and mobile subscribers. SUIT makes use of layered multiple description video coding and therefore promotes video scalability over broadcasting networks.

A memory-assisted lossless compression algorithm for medical images

Rapid growth of emerging medical applications such as e-health and tele-medicine requires fast, low cost, and often lossless access to massive amount of medical images and data over bandlimited channels. In this paper, we first show that significant amount of correlation and redundancy exist across different medical images. Such a correlation can be utilized to achieve better compression, and consequently less storage and less communication overhead on the network. We propose a novel memory-assisted compression technique, as a learning-based universal coding, which can be used to complement any existing algorithm to further eliminate redundancies across images. The approach is motivated by the fact that, often in medical applications, massive amount of correlated images from the same family are available as training data for learning the dependencies and deriving appropriate reference models. Such models can then be used for compression of any new image from the same family. In particular, Principal Component Analysis (PCA) is applied on a set of images from training data to form the required reference models. The proposed memory-assisted compression allows each image to be processed independently of other images, and hence allows individual image access and transmission. Experimental results on X-ray images show that the proposed algorithm achieves 20% improvement over and above traditional lossless image compression methods reported in the literature.

802.11G WLAN modeling for real time packet communication

This work proposes a statistical model of packet arrival and loss for wireless indoor environments in infrastructure mode. Usually, a Markov model with two states (Gilbert-Elliott, 1965) is used to model random processes of erroneous bits or packets. If we consider an equivalent model without memory, i.e. a random variable representing the burst length, then the Gilbert-Elliott model has a geometric distribution. We propose a statistical model for burst lengths of received and lost real time packets based on the logarithmic series distribution. We make use of a goodness-of-fit chi-square test to prove that our model surpasses the Gilbert-Elliott for 802.11g channels. Despite our model has been tested in a particular wireless scenario, it could also model other communications systems.