Mohsen Shaaban

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.

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.

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.

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 New Efficient Block-Matching Algorithm for Motion Estimation

This paper presents a new full-search block-matching algorithm: Multi-stage Interval-based Motion Estimation algorithm (MIME). The proposed algorithm is a block based motion estimation algorithm that utilizes successive elimination technique. We define two approximate functions, as the upper and lower boundaries of the interval that includes the Conventional distortion metric SAD. Each stage in the proposed algorithm; except for the last stage; incorporates low resolution pixels for the boundary functions calculations. The final stage is a full resolution block matching stage. MIME has a high probability of finding the optimal motion vector at any stage of the algorithm. The proposed algorithm reduces the computational complexity by successively eliminating non-candidate blocks from the search window at each stage. This computational reduction leads to enhanced performance in terms of low power consumption and fast motion vector estimation. A low power VLSI implementation of the algorithm is also presented in this paper. Simulation results on benchmark video sequences shows that MIME algorithm eliminates almost 88% of the candidate blocks after only two interval based stages.

A Low Complexity Inter Mode Decision for MPEG-2 to H.264/AVC Video Transcoding in Mobile Environments

This paper presents a fast variable block size Inter mode decision algorithm suitable for low complexity MPEG-2 to H.264/AVC heterogeneous video transcoding in mobile environments. Macroblock Inter coding mode prediction in H.264/AVC represents almost 70% of its computational complexity. An efficient transcoder would take advantage of the information stored in MPEG-2 bitstream (ex. motion vectors, DCT coefficients, etc.) to simplify macroblock mode decision in H.264/AVC. The proposed Fast Variable Block Size Inter Mode Decision (FVBSMD) algorithm conditionally reuse MPEG-2 motion vectors along with only few DCT coefficients to eliminate unnecessarily complexity from H.264/AVC variable block size motion re-estimation process. Simulations results; using video sequences with different motion complexities, resolutions and frame rates; show about 80% computational complexity elimination with only a 0.2dB and 2.5% degradation in PSNR and bit-rate respectively.

An Efficient Adaptive High Speed Manipulation Architecture for Fast Variable Padding Frequency Domain Motion Estimation

Motion estimation (ME) consumes up to 70% of the entire video encoders computations and is, therefore, the main encoding-time consuming process. Discrete cosine transform (DCT)-based phase correlation along with dynamic padding (DP) are the recently evolved frequency domain ME (FDME) techniques that promise to efficiently reduce the computational complexity of the ME process. DP uses dynamic padding thresholds to select the proper search area size according to a pre-estimated set of motion vectors (MVs). The main drawbacks of using conventional DP in the frequency domain are two-fold. First, the dynamic thresholds need to be estimated in the pixel (IDCT) domain which increases complexity. Second, the mismatched transformed search area is formed from different successive transformed blocks, which would lead to an inaccurate ME if the search area is not manipulated. In this paper, an efficient low complexity algorithm and high speed architecture are proposed to implement an adaptive manipulation unit engine (MUE). The MUE, the main module of the FDME system, adaptively decides the padding size and forges a matched transformed search area from the successive transformed blocks. Additionally, the proposed utilized dynamic thresholds are efficiently estimated in the frequency domain (FD). The MUE architecture is presented with two different design implementations trading off the VLSI design parameters. Implementation and simulation results project that the proposed MUE, when integrated in a whole FDME system, can perform ME for 60 fps of 4CIF video at 172 MHz.

An efficient adaptive manipulation architecture for real time video coding in Frequency Domain

Motion estimation (ME) consumes approximately up to 70% of the entire video encoders computations and is its main exhaustive time consuming process. Frequency-Domain Motion Estimation (FDME) evolved as a technique that would greatly reduce ME computations and the whole encoding time. In Dynamic Padding FDME (DP-FDME), a dynamic padding threshold adaptively selects the proper search area size according to a pre-estimated set of motion vectors. The main drawback of DP is the mismatched transformed search area formed from different consecutive transformed blocks which would lead to inaccurate ME. In this paper, efficient high speed architecture is proposed to implement an adaptive Manipulation Unit Engine (MUE), a main module of DP-FDME system, to forge a matched transformed search area from successive transformed blocks. Implementation results nominate the proposed MUE architecture to those multimedia applications that favors high speed processing as a trade-off to an acceptable increase in area and power. Simulation results project that MUE, when integrated in a whole FDME system, can perform ME for 60 fps of 4CIF video at 172 MHZ.

Motion estimation algorithm for real-time systems

The paper presents an algorithmic enhancement of the full-search block-matching algorithm for motion estimation for real-time systems. The multi-stage interval based motion estimation (MIME) algorithm reduces the computational load by successively eliminating candidate blocks from the search window. The elimination process uses low bit-resolution and it is applied in multiple stages for motion vector computation. On average, MIME eliminates more than 88% of the candidate blocks in the search window after the first and second stage. Based on these results, in a real-time environment, the algorithm can be stopped at any stage without incurring significant loss in motion estimation accuracy. Simulation results show that, in the worst case scenario when the algorithm stops after first stage, there is an average loss of only 3 dB in PSNR as compared to the full-search block-matching algorithm and an average loss of 1.2 dB if the algorithm is stopped after the second step.

Memory accesses reduction for MIME algorithm

Power consumption of digital systems has become a critical design parameter. An important class of digital systems includes applications such as video image processing and speech recognition, which are extremely memory dominant. In such systems, a significant amount of power is consumed during memory accesses. Reducing the number of memory accesses can considerably impact the power dissipation in the rest of the design. Therefore, optimizing an application for reduced memory access can greatly effect the overall power consumption in the entire system. This paper presents an architectural enhancement multi-stage interval-based motion estimation (MIME) algorithm that not only saves power by reducing the number of memory accesses but also significantly increases the speedup.