Efficient cost measures for motion compensation at low bit rates
17
Citation
11
Reference
10
Related Paper
Abstract:
We make a case that, even with severe efficiency constraints, taking the number of bits to code each motion vector into account when estimating motion for video compression results in significantly better performance at low bit rates, using simulation studies on established benchmark image sequences. In particular, we examine an algorithm that differs from a "vanilla" implementation of the H.261 standard by choosing motion vectors to minimize a cost function of prediction error and the number of bits to code a particular motion vector, where the coefficients of the cost function are adapted on-line using the Widrow-Hoff (1960) rule. We show that this algorithm performs comparably to a variety of more idealized, computationally intensive methods we examined in earlier papers and substantially better than the original "vanila" method, which ignores the number of bits to code the motion vector when choosing it.Keywords:
Quarter-pixel motion
Motion vector
Code (set theory)
Benchmark (surveying)
Bit (key)
Motion estimation is important for compression of video sequences. In this paper a new block motion estimation algorithm proposed. In the proposed method, the motion vector of previous frame are used to predict the initial motion vector and the search direction. The extent of search region is determined by predicted motion vector and motion vectors of four casual neighbours in the current frame. Results shows significant speed-up compared to existing ones.
Quarter-pixel motion
Motion vector
Inter frame
Motion field
Cite
Citations (1)
In H.264, 7 modes {1616, 168, 816, 88, 84, 48, 44) are used to enhance the coding efficiency. The motion vector estimation with 7 modes may require huge computing time. In this paper, to speed up the motion vector estimation procedure while the high image quality remains, we propose a motion vector refinement scheme using the temporary motion vector generated with little computation. The proposed estimation process consists of three phases: Mode decision for a 1616 macroblock, Composing a temporary motion vector, Refinement of the temporary motion vector. We demonstrate the effectiveness of the proposed method by computer simulation. In the results, the encoding time consumed by the proposed scheme has been reduced significantly while the encoded video quality remains unchanged.
Motion vector
Quarter-pixel motion
Macroblock
Cite
Citations (1)
Classical block-based motion-compensated video coders need to find and code a motion field with one motion vector per image block. All motion vectors are computed and encoded with the same fixed accuracy, typically 1 or one-half pixel accuracy. Higher motion vector accuracies have been shown to significantly reduce the total bit rate in some video sequences, but motion estimation at such subpixel accuracies is computationally expensive and is usually not performed in practice. In this paper we show that computing and encoding different motion vectors with different accuracies in the same frame can significantly reduce the total bit rate, and that the complexity of the block adaptive motion estimation procedure can be as low as that of the classical motion estimation at 1 pixel accuracy. Our new block adaptive motion estimator uses a simple technique to decide how accurately to compute the motion vector for each block. This technique results from an analysis on the effect of the motion vector accuracy on the total bit rate, and indicates that motion vectors of higher texture blocks must be computed more accurately and that at higher levels of compression lower motion vector accuracies are needed. We implement two video coders based on our technique, present results on real video frames, and describe the rate/complexity benefits of our procedure.
Quarter-pixel motion
Motion vector
Inter frame
Motion field
Subpixel rendering
Frame rate
Cite
Citations (4)
As a result of a combination of template comparison for estimating block similarity, edge selection algorithms and an improved block search method, two versions of a generalized method for finding motion vectors, called TFEMVFAS (Three by Frame Edge Map Motion Vector Field Adaptive Search), were proposed. Both modifications of the method were tested according to the comprehensive testing recommendations of the international commission MPEG for the evaluation of complex video tools, on the example of 13 video sequences, with different bitrates. The effect of increasing the size of the blocks on which the image is divided on the PSNR value and the maximum acceleration was also investigated.
Motion vector
Quarter-pixel motion
Cite
Citations (0)
Motion estimation is important for compression of video sequences. In this paper a new block motion estimation algorithm proposed. In the proposed method, the motion vector of previous frame are used to predict the initial motion vector and the search direction. The extent of search region is determined by predicted motion vector and motion vectors of four casual neighbours in the current frame. Results shows significant speed-up compared to existing ones.
Quarter-pixel motion
Motion vector
Inter frame
Motion field
Cite
Citations (1)
In H.264 standard, a lot of computational complexity is consumed in the encoder for motion estimation. It allows seven block sizes to perform the motion/compensation, and refers to previous five frames for searching the best motion vector to achieve lower bitrate and higher quality. Since the H.264 reference software uses the full search scheme to obtain the best performance, it spends a lot of searching time. In this paper we propose efficient searching algorithms by reuse of the motion vector information from the last reference frame. The proposed algorithms use the stored motion vectors to compose the current motion vector without performing the full search in each reference frame. Therefore, our proposed algorithms can obtain the speed up ratio 4 in average for encoding, which benefits from the prediction of the motion vector for reference frames in advance and maintain a good performance. Any fast search algorithm can be utilized to further largely reduce the computational load for the motion estimation from previous one frame.
Quarter-pixel motion
Motion vector
Inter frame
Cite
Citations (50)
Motion estimation is one of the key technologies in inner-frame estimation encoding of video compression. In all kinds of compression standard, motion estimation based on block is used widely. The H.264 was a kind of new generation video compression standard. In order to reduce the computational complexity of the motion estimation and improve the accuracy of motion compensation, a new search algorithm based on campaign features is pointed out. An adaptive model for starting point prediction is presented. And an alterable search pattern is introduced to improve the searching efficiency by adjusting its shape according to the motion characteristics. Experimental results show the new algorithm has better image quality and speed of the search advantage.
Quarter-pixel motion
Inter frame
Rate–distortion optimization
Cite
Citations (1)
The efficient motion estimation algorithms are the important research hotspot in the real-time video coding-decoding technology.The prediction error can be decreased by incorporating high accuracy estimation and compensation,and the performance of compressed video can be improved.The high computational demands of the H.264 video encoder are reduced by an deformable block-matching algorithm using the node-based model.This algorithm well exploits the motion vector statistic characteristic and correlation and uses motion estimation criterion based on the pixel difference classify.Experiments show that the efficient motion estimation algorithm proposed can further reduce block matching distortion computations relative to conventional fast motion estimation algorithms with neglectable coding efficiency loss.
Quarter-pixel motion
Motion vector
Rate–distortion optimization
Algorithmic efficiency
Cite
Citations (0)
The popular techniques to eliminate temporal redundancy in video sequences are Motion Estimation and Motion Compensation. These techniques have also been used in popular H.264, MPEG-2 and MPEG-4 video coding standards. Conventional fast Block Matching Algorithms (BMA) perform exhaustive search between the current and the reference frame. Although BMA technique gives the exact result but it is computationally very expensive. Another drawback of this method is that it easily gets trapped into the local minima which eventually lead to degradation of the video quality. The proposed Motion Estimation Technique exploits the fact that the human eyes are incapable of detecting different frames when they are run at particular frame rate. The experimental results on various video sequences demonstrate that the proposed technique has outperformed all the existing conventional motion estimation techniques.
Quarter-pixel motion
Inter frame
Rate–distortion optimization
Cite
Citations (2)
Most image coding algorithms, like the P X 64 and MPEG-1 standards, use locally derived estimates of object motion to form a prediction of the current frame. But camera motion, such as zooms and pans, which systemically affect the entire frame, is seldom handled efficiently. In this paper, we study the modeling, estimation and compensation of global motion caused by camera zooms and pans, we model the global motion in each frame with just two parameters: a scalar zoom factor and a 2D pan vector. Parameter estimation minimizes the squared prediction error of either the difference frame or the optical flow field. The estimated parameters are then used to construct a zoom/pan compensated prediction of the current frame, upon which some local motion compensation algorithm can then be applied to model object motion. Simulations suggest that these two global motion estimation algorithms are robust and accurate, and that global motion compensation provides a better prediction of the current frame with a potentially large reduction of motion side information.
Quarter-pixel motion
Optical Flow
Motion vector
Motion field
Inter frame
Cite
Citations (11)