Yasser Ismail

Fast Motion Estimation System Using Dynamic Models for H.264/AVC Video Coding

H.264/AVC offers many coding tools for achieving high compression gains of up to 50% more than other standards. These tools dramatically increase the computational complexity of the block based motion estimation (BB-ME) which consumes up to 80% of the entire encoders computations. In this paper, computationally efficient accurate skipping models are proposed to speed up any BB-ME algorithm. First, an accurate initial search center (ISC) is decided using a smart prediction technique. Thereafter, a dynamic early stop search termination (DESST) is used to decide if the block at the ISC position can be considered as a best match candidate block or not. If the DESST algorithm fails, a less complex style of the motion estimation algorithm which incorporates dynamic padding window size technique will be used. Further reductions in computations are achieved by combining the following two techniques. First, a dynamic partial internal stop search technique which utilizes an accurate adaptive threshold model is exploited to skip the internal sum of absolute difference operations between the current and the candidate blocks. Second, a dynamic external stop search technique greatly reduces the unnecessary operations by skipping all the irrelevant blocks in the search area. The proposed techniques can be incorporated in any block matching motion estimation algorithm. Computational complexity reduction is reflected in the amount of savings in the motion estimation encoding time. The novelty of the proposed techniques comes from their superior saving in computations with an acceptable degradation in both peak signal-to-noise ratio (PSNR) and bit-rate compared to the state of the art and the recent motion estimation techniques. Simulation results using H.264/AVC reference software (JM 12.4) show up to 98% saving in motion estimation time using the proposed techniques compared to the conventional full search algorithm with a negligible degradation in the PSNR by approximately 0.05 dB and a small increase in the required bits per frame by only 2%. Experimental results also prove the effectiveness of the proposed techniques if they are incorporated with any fast BB-ME technique such as fast extended diamond enhanced predictive zonal search and predictive motion vector field adaptive search technique.

Adaptive search window size algorithm for fast motion estimation in H.264/AVC standard

H.264/AVC is a new recommendation for moving picture coding, in which a lot of new techniques are used for improving encoding efficiency and reducing the bit-rate. However, it involves an exhaustive motion search across multiple block sizes and multiple reference frames leading to a linear increase in processing time. Although, the encoding quality is improved, the complexity of the encoder and computational cost are increased at the same time. We reduce the computational cost by reducing the search space without significant loss in quality. Results show that there is at least 90% reduction in computation with a maximum loss of 1.4dB.

An Efficient Data Reuse Motion Estimation Engine

We present a novel motion estimation engine (MEE) architecture that efficiently reuses search area data while fully utilizing the hardware resources. A 2-D processing element (PE) core is central to the architecture. Search area data flows both horizontally as well as vertically while the current block data is stationary. A clever PE design ensures simple but highly regular dataflow through the core avoiding long interconnect delays. For a search range of [-16,+15] and block size of 16, our architecture can perform motion estimation for 60 fps of 4CIF video at 100 MHz

Fast Variable Padding Motion Estimation Using Smart Zero Motion Prejudgment Technique for Pixel and Frequency Domains

Motion estimation (ME) plays an important role in modern video coders since it consumes approximately 60-80% of the entire encoders computations. In this paper, three novel techniques are proposed to effectively speed up the ME process. First, a smart prediction technique for effectively deciding an initial search center is proposed. Second, a zero motion prejudgment technique is proposed to accurately decide whether the pre-estimated ISC can be considered as a best match motion vector (MV) and consequently save the required computations for the MV refinement process. Finally, a variable padding pixels ME technique is proposed to adaptively determine the number of padding pixels required for the search window for more computational cost savings. The three techniques are combined and applied to the block-based ME for a superior computational complexity savings in the ME process. The performance of the proposed techniques is tested in both the pixel domain ME and the frequency domain ME in terms of their quantitative visual quality (peak signal-to-noise ratio, PSNR), their computational complexity, and their bit rate. Experimental results demonstrate that the proposed fast ME technique is able to achieve approximately a 99.4% reduction in ME time compared to the conventional full search block-based ME (FSSBB-ME) with negligible degradation in both the PSNR and the bit rate. Additionally, the experimental results prove the effectiveness of the proposed techniques if they are combined with any block-based ME technique such as the fast extended diamond enhanced predictive zonal search. Experimental results also demonstrate that there is at least an additional savings of 72% in ME time using the conventional discrete cosine transform phase correlation ME (DCT-PC-ME) in the frequency domain compared to the conventional FSBB-ME technique in pixel domain. Compared to the conventional DCT-PC-ME, applying the proposed novel techniques to the DCT-PC-ME saves up to 89% in ME time.

Enhanced efficient Diamond Search algorithm for fast block motion estimation

In this paper, a Modified Diamond Search (MDS) algorithm is proposed for fast motion estimation based on the well known Diamond Search (DS) algorithm. A set of computationally efficient algorithms that can be applied to any block matching algorithm and is applied to the DS as a study case achieves higher complexity reduction than DS algorithm without further relative PSNR (peak signal to noise ratio) degradation compared to Full Search (FS). First, Dynamic Internal Stop Search (DISS) algorithm is used to reduce the internal redundant SAD (Sum of Absolute Difference) operations between the current and the candidate blocks using an accurate dynamic threshold. Second, a Dynamic External Stop Search (DESS) greatly reduces the unnecessary operations by skipping all the irrelevant blocks in the search area. In addition, early search termination and adaptive pattern selections techniques are applied to the proposed MDS as initialization steps to achieve even higher complexity reduction. The accuracy of the proposed model threshold equations guarantee not to fall into a local minima. Experiments show that the proposed MDS algorithm reduces the computations greatly up to 99% and 20% compared with the conventional FS algorithm and DS respectively with no significant degradation in both the PSNR and the bit-rate.

Adaptive Techniques for a Fast Frequency Domain Motion Estimation

Dynamic Block Size Motion Estimation (DBS-ME) and smart Dynamic Early Search Termination (DEST) techniques are proposed and implemented in this paper. Both of the proposed techniques are combined and applied to the conventional phase correlation technique. The performance, visual quality and complexity of the proposed techniques are compared to that of the original phase correlation motion estimation (PC-ME) and Full Search Block Matching (FSBM) techniques. The proposed techniques provide an increase in the encoding quality besides a decrease in the computational complexity of ME process. Results show that there is approximately 100% of the stationary blocks decided by the FSBM algorithm are discovered correctly which consequently reduce the computations compared with the original FS and PC techniques. Also it is noted that, DBS-ME technique greatly decreases the computations required for ME process by decreasing the required padding to one or two pixels for both the current and the reference blocks. In addition, the motion field of the proposed algorithm gives much lower entropy than PC-ME which means more reduction in the transmitted bit rate.

An Adaptive Block Size Phase Correlation Motion Estimation Using Adaptive Early Search Termination Technique

An adaptive block size phase correlation motion estimation (ABSPC-ME) with a smart adaptive early termination technique is proposed and implemented in this paper. With its performance, efficiency and complexity ABSPC-ME is compared to that of the original phase correlation (PC) and full search block matching (FSBM) techniques. Since the phase correlation method measures the motion directly from the phase correlation map, it gives a more accurate and robust estimate of the motion vector. Besides increasing the encoding quality, the complexity of the encoder and computational cost are also decreased. Results show that there is approximately 78% reduction in computations compared with the original PC technique and 96% compared with FSBM without a significant loss in the visual quality.

High-speed Motion Estimation Architecture for Real-time Video Transmission

Motion estimation (ME) process consumes up to 70% of the total encoding time of video transmission. Because it has a high coding efficiency and it is very scalable, the full search (FS) algorithm is considered to be the most popular ME algorithm. However, the main drawback of the FS algorithm is that it is computationally intensive. For this reason, FS is rarely used for real-time video coding. This paper proposes a simple and fast adaptive search window size (ASWS) algorithm that eliminates a significant amount of computations from the conventional FS algorithm. This is achieved by dynamically reducing the required search area for each reference block. Simulation results show that more than 94% of the candidate blocks are eliminated by our algorithm without significant loss in visual quality. This paper also presents an efficient and high-speed ME engine (MEE) architecture for the proposed ASWS algorithm. The MEE efficiently reuses the search area data to minimize the memory I/O while fully utilizing the available hardware resources. A smart processing element design along with an innovative data scheduling scheme allows the search area data to flow both horizontally and vertically, whereas the current block data remain stationary. This allows the proposed architecture a simple and highly regular dataflow through the core. Simulation results show that for a search range of [-16,+15] and a block size of 16×16, the proposed architecture performs the ME for 60 fps of 4CIF video at 100 MHz and easily outperforms many FS architectures.

A generalized fast motion estimation algorithm using external and internal stop search techniques for H.264 video coding standard

In this paper, a set of computationally efficient accurate skipping techniques are proposed for motion estimation. First, a partial internal stop search (ISS) technique which utilizes an accurate adaptive threshold model is exploited to skip the internal SAD (sum of absolute difference) operations between the current and reference blocks. Second, an external stop search (ESS) technique greatly reduces the unnecessary operations by skipping all the irrelevant blocks in the search area. The proposed techniques can be incorporated in any block matching motion estimation algorithm. Computational complexity reduction is reflected on the amount of saving in motion estimation encoding time. Simulation results using H.264 reference software (JM 12.4) show up to 71.26% saving in motion estimation time using the proposed techniques compared to the fast full search algorithm adopted in JM 12.4 with a negligible degradation in the PSNR by approximately 0.03 dB and a small increase in the required bits per frame by only 2%.

A fast block-based motion estimation using early stop search techniques for H.264/AVC standard

H.264/AVC is a new video coding standard of the ITU-T video coding expert group which has a significant improvement in the rate distortion efficiency compared with the previous standards. However, there is an exhaustive motion search across multiple block sizes and multiple reference frames leading to a linear increase in processing time. Although, the encoding quality is improved, the complexity of the encoder and computational cost are also increased at the same time. In this paper, we reduce the computational cost by reducing the number of candidate pixels required for the sum of absolute difference for each block (SAD) using two early stop search techniques. These techniques are applied on two scan search patterns (raster and spiral search patterns) and compared with the conventional full search (FS), three step search (TSS), and diamond search (DS) algorithms. Results show that there is at least 98% reduction in computations with a maximum loss of 0.1 dB compared with the conventional FS algorithm.