The Wyner-Ziv distributed video coding scheme is characterized for its intraframe encoder and interframe decoder which can also approach the efficiency of an interframe encoder-decoder system. In Wyner-Ziv residual co...The Wyner-Ziv distributed video coding scheme is characterized for its intraframe encoder and interframe decoder which can also approach the efficiency of an interframe encoder-decoder system. In Wyner-Ziv residual coding of video, the residual of a frame with respect to a reference frame is Wyner-Ziv encoded, which can reduces the input entropy and leads to a higher coding efficiency than directly encoding the original frame. In this paper, we propose a new approach of residual coding combined with Region Of Interest (ROI) extraction. Experimental results show that, the proposed scheme achieves better rate-distortion performance compared to conventional Wyner-Ziv coding scheme.展开更多
Side information （SI） is one of the key issues in distributed video coding （DVC） and affects the compression performance of DVC largely. This paper proposes an SI refinement algorithm, in which the Wyner-Ziv （WZ...Side information （SI） is one of the key issues in distributed video coding （DVC） and affects the compression performance of DVC largely. This paper proposes an SI refinement algorithm, in which the Wyner-Ziv （WZ） frame is split into two parts based on checkerboard pattern, and the two parts are encoded independently but decoded sequentially. In the decoding process, the part 1 is first decoded with the initial SI and partially decoded part （PDP） 1 is used to improve the motion vectors （MVs） and SI of both parts. At the next stage, the part 2 is decoded with the improved SI and PDP 2 is used to further refine MVs of the part 2. Then, SI of both parts are further refined. Simulation results show that the proposed algorithm can improve the peak signal to noise ratio （PSNR） by up to 1.43 dB when compared with traditional DVC codec.展开更多
This paper proposes a maximum a posteriori （MAP） based blocking artifact reduction algorithm for discrete cosine transform （DCT） domain distributed video coding, in which the SI and the initial reconstructed Wyner...This paper proposes a maximum a posteriori （MAP） based blocking artifact reduction algorithm for discrete cosine transform （DCT） domain distributed video coding, in which the SI and the initial reconstructed Wyner-Ziv （WZ） frame are utilized to further estimate the original WZ frame. Though the MAP estimate improves quality of the artifact region, it also leads to over-smoothness and decreases quality of the non-artifact region. To overcome this problem, a criterion is presented to discriminate the artifact and the non-artifact region in the initial reconstructed WZ frame, and only the artifact region is updated with the MAP estimate. Simulation results show that the proposed algorithm provides obvious improvement in terms of both objective and subjective evaluations.展开更多
Popular video coding standards like H.264 and MPEG working on the principle of motion-compensated pre-dictive coding demand much of the computational resources at the encoder increasing its complexity. Such bulky enco...Popular video coding standards like H.264 and MPEG working on the principle of motion-compensated pre-dictive coding demand much of the computational resources at the encoder increasing its complexity. Such bulky encoders are not suitable for applications like wireless low power surveillance, multimedia sensor networks, wireless PC cameras, mobile camera phones etc. New video coding scheme based on the principle of distributed source coding is looked upon in this paper. This scheme supports a low complexity encoder, at the same time trying to achieve the rate distortion performance of conventional video codecs. Current im-plementation uses LDPC codes for syndrome coding.展开更多
In the frame of compressed sensing distributed video coding, the design of the quantization matrix directly affects the reconstruction quality of the receiving terminal of the video. In this article, we present a new ...In the frame of compressed sensing distributed video coding, the design of the quantization matrix directly affects the reconstruction quality of the receiving terminal of the video. In this article, we present a new design method of the Gaussian quantization matrix adapting to the compressed sensing coding, for that the distribution of the parameters of the image is featured of the characteristic of approximately normal distribution after measured by compressive sensing. By this way, the parameters of a certain quantity of the image frames depending on the video sequences generated by the Gaussian quantization matrix possess certain adaptive capacity. By comparison with the plan of the traditional quantization, the quantization matrix presented in this article would improve the reconstruction quality of the video.展开更多
Compressed sensing(CS)is a novel technology to acquire and reconstruct sparse signals below the Nyquist rate.It has great potential in image and video acquisition and processing.To effectively improve the sparsity of ...Compressed sensing(CS)is a novel technology to acquire and reconstruct sparse signals below the Nyquist rate.It has great potential in image and video acquisition and processing.To effectively improve the sparsity of signal being measured and reconstructing efficiency,an encoding and decoding model of residual distributed compressive video sensing based on double side information(RDCVS-DSI)is proposed in this paper.Exploiting the characteristics of image itself in the frequency domain and the correlation between successive frames,the model regards the video frame in low quality as the first side information in the process of coding,and generates the second side information for the non-key frames using motion estimation and compensation technology at its decoding end.Performance analysis and simulation experiments show that the RDCVS-DSI model can rebuild the video sequence with high fidelity in the consumption of quite low complexity.About 1~5 dB gain in the average peak signal-to-noise ratio of the reconstructed frames is observed,and the speed is close to the least complex DCVS,when compared with prior works on compressive video sensing.展开更多
In Wyner-Ziv (WZ) Distributed Video Coding (DVC), correlation noise model is often used to describe the error distribution between WZ frame and the side information. The accuracy of the model can influence the perform...In Wyner-Ziv (WZ) Distributed Video Coding (DVC), correlation noise model is often used to describe the error distribution between WZ frame and the side information. The accuracy of the model can influence the performance of the video coder directly. A mixture correlation noise model in Discrete Cosine Transform (DCT) domain for WZ video coding is established in this paper. Different correlation noise estimation method is used for direct current and alternating current coefficients. Parameter estimation method based on expectation maximization algorithm is used to estimate the Laplace distribution center of direct current frequency band and Mixture Laplace-Uniform Distribution Model (MLUDM) is established for alternating current coefficients. Experimental results suggest that the proposed mixture correlation noise model can describe the heavy tail and sudden change of the noise accurately at high rate and make significant improvement on the coding efficiency compared with the noise model presented by DIStributed COding for Video sERvices (DISCOVER).展开更多
A novel Compressed-Sensing-based(CS-based)Distributed Video Coding(DVC)system,called Distributed Adaptive Compressed Video Sensing(DISACOS),is proposed in this paper.In this system,the input frames are divided into ke...A novel Compressed-Sensing-based(CS-based)Distributed Video Coding(DVC)system,called Distributed Adaptive Compressed Video Sensing(DISACOS),is proposed in this paper.In this system,the input frames are divided into key frames and non-key frames,which are encoded by block CS sampling.The key frames are encoded as CS measurements at substantially higher rates than the non-key frames and decoded by the Smoothed Projected Landweber(SPL)algorithm using multi-hypothesis predictions.For the non-key frames,a small number of CS measurements are first transmitted to detect blocks having low-quality Side Information(SI)generated by the conventional interpolation or extrapolation at the decoder;then,another group of CS measurements are sampled again upon the decoder’s request.To fully utilise the CS measurements,we adaptively allocate these measurements to each block in terms of different edge features.Finally,the residual frame is reconstructed using the SPL algorithm and the decoded non-key frame is simply determined as the sum of the residual frame and the SI.Experimental results have revealed that our CS-based DVC system yields better rate-distortion performance when compared with other schemes.展开更多
Distributed video coding （DVC） is a new video coding approach based on Wyner-Ziv theorem. The novel uplink-friendly DVC, which offers low-complexity, low-power consuming, and low-cost video encoding, has aroused mor...Distributed video coding （DVC） is a new video coding approach based on Wyner-Ziv theorem. The novel uplink-friendly DVC, which offers low-complexity, low-power consuming, and low-cost video encoding, has aroused more and more research interests. In this paper a new method based on multiple view geometry is presented for spatial side information generation of uncalibrated video sensor network. Trifocal tensor encapsulates all the geometric relations among three views that are independent of scene structure; it can be computed from image correspondences alone without requiring knowledge of the motion or calibration. Simulation results show that trifocal tensor-based spatial side information improves the rate-distortion performance over motion compensation based interpolation side information by a maximum gap of around 2dB. Then fusion merges the different side information （temporal and spatial） in order to improve the quality of the final one. Simulation results show that the rate-distortion gains about 0.4 dB.展开更多
为提高分布式视频编码系统解码WZ(Wyner-Ziv)帧的图像质量,提出了基于广义高斯分布的WZ帧重构算法.该算法充分考虑了边信息与原始WZ帧具有较强相关性的特点,将广义高斯分布作为相关模型;在边信息已知情况下,对给定量化区间、计算WZ帧的...为提高分布式视频编码系统解码WZ(Wyner-Ziv)帧的图像质量,提出了基于广义高斯分布的WZ帧重构算法.该算法充分考虑了边信息与原始WZ帧具有较强相关性的特点,将广义高斯分布作为相关模型;在边信息已知情况下,对给定量化区间、计算WZ帧的条件期望并将其作为WZ重构值;将广义高斯分布的形状参数设为0.5,推导出基于广义高斯分布重构WZ帧的闭式表示.实验结果表明,文中提出的基于广义高斯分布的WZ帧重构算法比最小均方误差(MMSE)重构算法的峰值信噪比提高约0.6 d B,并能有效改善重构WZ帧的图像质量.展开更多
边信息质量是影响基于深度图的多视点分布式视频编码(DMDVC)系统压缩效率的关键因素之一。为了充分利用时域边信息、空域边信息及深度图来提升DMDVC系统的边信息质量,提出一种基于可靠性评估的融合算法。首先采用运动补偿时域内插(MCTI...边信息质量是影响基于深度图的多视点分布式视频编码(DMDVC)系统压缩效率的关键因素之一。为了充分利用时域边信息、空域边信息及深度图来提升DMDVC系统的边信息质量,提出一种基于可靠性评估的融合算法。首先采用运动补偿时域内插(MCTI)算法生成时域边信息,然后采用基于深度图的视点绘制(DIBR)技术生成空域边信息。针对场景中物体快速运动会影响时域边信息质量以及利用DIBR技术生成空域边信息时会产生空洞等问题,有选择地对时域边信息的运动剧烈区域或空域边信息的空洞及边缘区域进行修正。实验结果表明,该算法可以有效地融合时域边信息和空域边信息,较参考文献[4]的融合算法最高可提升5.6 d B。展开更多
针对现有内插结构无反馈分布式视频压缩(DVC)在大图像组条件下存在严重解码延时问题,研究了外推结构的无反馈DVC系统。在编码端,提出一种不等保护码率控制算法,该算法在编码端利用快速运动估计外推产生较高质量的边信息估计,根据比特平...针对现有内插结构无反馈分布式视频压缩(DVC)在大图像组条件下存在严重解码延时问题,研究了外推结构的无反馈DVC系统。在编码端,提出一种不等保护码率控制算法,该算法在编码端利用快速运动估计外推产生较高质量的边信息估计,根据比特平面误码率和比特平面重要性,实现比特平面级的码率控制;在解码端提出基于外推内插边信息更新的迭代解码优化,利用更新的边信息对每一分布式帧进行二次解码,在不增加传输码率的条件下进一步提升解码视频质量。实验结果表明,与现有无反馈码率分配算法相比,该算法能够更精确地分配码率,率失真性能提升0.6~1.8 d B,且解码视频图像的主观质量得到明显改善。展开更多
现有的分块视频压缩感知在获取边信息时,通常对所有图像块均采用固定权值边信息合成方法,该方法忽略了不同图像块之间相关度不同的问题。针对这一问题,根据贝叶斯压缩感知和运动估计理论,提出了一种基于块的分类加权边信息生成方案的分...现有的分块视频压缩感知在获取边信息时,通常对所有图像块均采用固定权值边信息合成方法,该方法忽略了不同图像块之间相关度不同的问题。针对这一问题,根据贝叶斯压缩感知和运动估计理论,提出了一种基于块的分类加权边信息生成方案的分布式视频解码方法。在解码端利用相邻关键帧中不同块的相关度差异,对相邻关键帧进行基于块的分类加权运动估计,生成边信息,进而完成非关键帧的重构。考虑到加权系数的大小取决于相邻关键帧对应块的相关度,所采用的重建算法是基于TSW-CS模型的贝叶斯压缩感知重构算法。分别采用固定权值边信息生成方法和分类加权边信息生成方法对不同视频序列进行了实验对比,实验结果表明,采用分类加权边信息方法生成的视频重建PSNR值比固定权值边信息生成方法平均提高了0.2~0.5 d B,所采用的解码方法可有效地提高视频压缩感知重构质量。展开更多
为了解决科考船对科考仪器主机进行远程控制,同时对视频数据进行远程显示的问题,"雪龙2"号科考破冰船进行了有效的探索。船载实验室采用KVM OVER IP(KVM为Keyboard、Video、Mouse的缩写,数字式多计算机切换器,简称IP KVM)和DV...为了解决科考船对科考仪器主机进行远程控制,同时对视频数据进行远程显示的问题,"雪龙2"号科考破冰船进行了有效的探索。船载实验室采用KVM OVER IP(KVM为Keyboard、Video、Mouse的缩写,数字式多计算机切换器,简称IP KVM)和DVCS(Distributed Video Control System,分布式控制系统,简称DVCS)技术,将科考仪器主机和视频显示系统通过网络连接在一起,实现了在科考船其他位置操作科考仪器主机,同时将需要远程显示的视频数据传输到需要的屏幕上。经过在极地现场的实际应用,两套系统操作方便、系统稳定、视频清晰、维护简单,为现场作业的科考队员提供了便利条件,也得到了科考队员的认可。展开更多
基金Supported by the National Natural Science Foundation of China (No.61003236, 61171053, 61170065)the Doctoral Fund of Ministry of Education of China (No.20113223110002)the Natural Science Major Program for Colleges and Universities in Jiangsu Province(No.11KJA520001)
文摘The Wyner-Ziv distributed video coding scheme is characterized for its intraframe encoder and interframe decoder which can also approach the efficiency of an interframe encoder-decoder system. In Wyner-Ziv residual coding of video, the residual of a frame with respect to a reference frame is Wyner-Ziv encoded, which can reduces the input entropy and leads to a higher coding efficiency than directly encoding the original frame. In this paper, we propose a new approach of residual coding combined with Region Of Interest (ROI) extraction. Experimental results show that, the proposed scheme achieves better rate-distortion performance compared to conventional Wyner-Ziv coding scheme.
基金Supported by the National Natural Science Foundation of China （ No. 60736043, 60672088） and the National Basic Research Program of China （No. 2009CB32005）.
文摘Side information （SI） is one of the key issues in distributed video coding （DVC） and affects the compression performance of DVC largely. This paper proposes an SI refinement algorithm, in which the Wyner-Ziv （WZ） frame is split into two parts based on checkerboard pattern, and the two parts are encoded independently but decoded sequentially. In the decoding process, the part 1 is first decoded with the initial SI and partially decoded part （PDP） 1 is used to improve the motion vectors （MVs） and SI of both parts. At the next stage, the part 2 is decoded with the improved SI and PDP 2 is used to further refine MVs of the part 2. Then, SI of both parts are further refined. Simulation results show that the proposed algorithm can improve the peak signal to noise ratio （PSNR） by up to 1.43 dB when compared with traditional DVC codec.
基金Supported by the National Natural Science Foundation of China （No.60672088, No.60736043） the National Basic Research Development Program of China （2009CB320905）
文摘This paper proposes a maximum a posteriori （MAP） based blocking artifact reduction algorithm for discrete cosine transform （DCT） domain distributed video coding, in which the SI and the initial reconstructed Wyner-Ziv （WZ） frame are utilized to further estimate the original WZ frame. Though the MAP estimate improves quality of the artifact region, it also leads to over-smoothness and decreases quality of the non-artifact region. To overcome this problem, a criterion is presented to discriminate the artifact and the non-artifact region in the initial reconstructed WZ frame, and only the artifact region is updated with the MAP estimate. Simulation results show that the proposed algorithm provides obvious improvement in terms of both objective and subjective evaluations.
文摘Popular video coding standards like H.264 and MPEG working on the principle of motion-compensated pre-dictive coding demand much of the computational resources at the encoder increasing its complexity. Such bulky encoders are not suitable for applications like wireless low power surveillance, multimedia sensor networks, wireless PC cameras, mobile camera phones etc. New video coding scheme based on the principle of distributed source coding is looked upon in this paper. This scheme supports a low complexity encoder, at the same time trying to achieve the rate distortion performance of conventional video codecs. Current im-plementation uses LDPC codes for syndrome coding.
文摘In the frame of compressed sensing distributed video coding, the design of the quantization matrix directly affects the reconstruction quality of the receiving terminal of the video. In this article, we present a new design method of the Gaussian quantization matrix adapting to the compressed sensing coding, for that the distribution of the parameters of the image is featured of the characteristic of approximately normal distribution after measured by compressive sensing. By this way, the parameters of a certain quantity of the image frames depending on the video sequences generated by the Gaussian quantization matrix possess certain adaptive capacity. By comparison with the plan of the traditional quantization, the quantization matrix presented in this article would improve the reconstruction quality of the video.
基金Supported by National Natural Science Foundation of China(61170147)Major Cooperation Project of Production and College in Fujian Province(2012H61010016)Natural Science Foundation of Fujian Province(2013J01234)
文摘Compressed sensing(CS)is a novel technology to acquire and reconstruct sparse signals below the Nyquist rate.It has great potential in image and video acquisition and processing.To effectively improve the sparsity of signal being measured and reconstructing efficiency,an encoding and decoding model of residual distributed compressive video sensing based on double side information(RDCVS-DSI)is proposed in this paper.Exploiting the characteristics of image itself in the frequency domain and the correlation between successive frames,the model regards the video frame in low quality as the first side information in the process of coding,and generates the second side information for the non-key frames using motion estimation and compensation technology at its decoding end.Performance analysis and simulation experiments show that the RDCVS-DSI model can rebuild the video sequence with high fidelity in the consumption of quite low complexity.About 1~5 dB gain in the average peak signal-to-noise ratio of the reconstructed frames is observed,and the speed is close to the least complex DCVS,when compared with prior works on compressive video sensing.
基金Supported by the National Natural Science Foundation of China (No. 61071091)Jiangsu Province Graduate Innovative Research Plan (CX07B_107Z)
文摘In Wyner-Ziv (WZ) Distributed Video Coding (DVC), correlation noise model is often used to describe the error distribution between WZ frame and the side information. The accuracy of the model can influence the performance of the video coder directly. A mixture correlation noise model in Discrete Cosine Transform (DCT) domain for WZ video coding is established in this paper. Different correlation noise estimation method is used for direct current and alternating current coefficients. Parameter estimation method based on expectation maximization algorithm is used to estimate the Laplace distribution center of direct current frequency band and Mixture Laplace-Uniform Distribution Model (MLUDM) is established for alternating current coefficients. Experimental results suggest that the proposed mixture correlation noise model can describe the heavy tail and sudden change of the noise accurately at high rate and make significant improvement on the coding efficiency compared with the noise model presented by DIStributed COding for Video sERvices (DISCOVER).
基金supported by the Graduate Student Research Innovation Project of Jiangsu Province China under Grants No. CXZZ12_0466, No. CXZZ11_0390the National Natural Science Foundation of China under Grants No. 61071091, No. 61271240+2 种基金the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province China under Grant No. 12KJB510019the Nanjing University of Posts and Telecommunications Natural Science Foundation under Grant No. NY212015the Technology Research Program of Hubei Provincial Department of Education under Grant No. D20121408
文摘A novel Compressed-Sensing-based(CS-based)Distributed Video Coding(DVC)system,called Distributed Adaptive Compressed Video Sensing(DISACOS),is proposed in this paper.In this system,the input frames are divided into key frames and non-key frames,which are encoded by block CS sampling.The key frames are encoded as CS measurements at substantially higher rates than the non-key frames and decoded by the Smoothed Projected Landweber(SPL)algorithm using multi-hypothesis predictions.For the non-key frames,a small number of CS measurements are first transmitted to detect blocks having low-quality Side Information(SI)generated by the conventional interpolation or extrapolation at the decoder;then,another group of CS measurements are sampled again upon the decoder’s request.To fully utilise the CS measurements,we adaptively allocate these measurements to each block in terms of different edge features.Finally,the residual frame is reconstructed using the SPL algorithm and the decoded non-key frame is simply determined as the sum of the residual frame and the SI.Experimental results have revealed that our CS-based DVC system yields better rate-distortion performance when compared with other schemes.
文摘Distributed video coding （DVC） is a new video coding approach based on Wyner-Ziv theorem. The novel uplink-friendly DVC, which offers low-complexity, low-power consuming, and low-cost video encoding, has aroused more and more research interests. In this paper a new method based on multiple view geometry is presented for spatial side information generation of uncalibrated video sensor network. Trifocal tensor encapsulates all the geometric relations among three views that are independent of scene structure; it can be computed from image correspondences alone without requiring knowledge of the motion or calibration. Simulation results show that trifocal tensor-based spatial side information improves the rate-distortion performance over motion compensation based interpolation side information by a maximum gap of around 2dB. Then fusion merges the different side information （temporal and spatial） in order to improve the quality of the final one. Simulation results show that the rate-distortion gains about 0.4 dB.
文摘为提高分布式视频编码系统解码WZ(Wyner-Ziv)帧的图像质量,提出了基于广义高斯分布的WZ帧重构算法.该算法充分考虑了边信息与原始WZ帧具有较强相关性的特点,将广义高斯分布作为相关模型;在边信息已知情况下,对给定量化区间、计算WZ帧的条件期望并将其作为WZ重构值;将广义高斯分布的形状参数设为0.5,推导出基于广义高斯分布重构WZ帧的闭式表示.实验结果表明,文中提出的基于广义高斯分布的WZ帧重构算法比最小均方误差(MMSE)重构算法的峰值信噪比提高约0.6 d B,并能有效改善重构WZ帧的图像质量.
文摘边信息质量是影响基于深度图的多视点分布式视频编码(DMDVC)系统压缩效率的关键因素之一。为了充分利用时域边信息、空域边信息及深度图来提升DMDVC系统的边信息质量,提出一种基于可靠性评估的融合算法。首先采用运动补偿时域内插(MCTI)算法生成时域边信息,然后采用基于深度图的视点绘制(DIBR)技术生成空域边信息。针对场景中物体快速运动会影响时域边信息质量以及利用DIBR技术生成空域边信息时会产生空洞等问题,有选择地对时域边信息的运动剧烈区域或空域边信息的空洞及边缘区域进行修正。实验结果表明,该算法可以有效地融合时域边信息和空域边信息,较参考文献[4]的融合算法最高可提升5.6 d B。
文摘针对现有内插结构无反馈分布式视频压缩(DVC)在大图像组条件下存在严重解码延时问题,研究了外推结构的无反馈DVC系统。在编码端,提出一种不等保护码率控制算法,该算法在编码端利用快速运动估计外推产生较高质量的边信息估计,根据比特平面误码率和比特平面重要性,实现比特平面级的码率控制;在解码端提出基于外推内插边信息更新的迭代解码优化,利用更新的边信息对每一分布式帧进行二次解码,在不增加传输码率的条件下进一步提升解码视频质量。实验结果表明,与现有无反馈码率分配算法相比,该算法能够更精确地分配码率,率失真性能提升0.6~1.8 d B,且解码视频图像的主观质量得到明显改善。
文摘现有的分块视频压缩感知在获取边信息时,通常对所有图像块均采用固定权值边信息合成方法,该方法忽略了不同图像块之间相关度不同的问题。针对这一问题,根据贝叶斯压缩感知和运动估计理论,提出了一种基于块的分类加权边信息生成方案的分布式视频解码方法。在解码端利用相邻关键帧中不同块的相关度差异,对相邻关键帧进行基于块的分类加权运动估计,生成边信息,进而完成非关键帧的重构。考虑到加权系数的大小取决于相邻关键帧对应块的相关度,所采用的重建算法是基于TSW-CS模型的贝叶斯压缩感知重构算法。分别采用固定权值边信息生成方法和分类加权边信息生成方法对不同视频序列进行了实验对比,实验结果表明,采用分类加权边信息方法生成的视频重建PSNR值比固定权值边信息生成方法平均提高了0.2~0.5 d B,所采用的解码方法可有效地提高视频压缩感知重构质量。
文摘为了解决科考船对科考仪器主机进行远程控制,同时对视频数据进行远程显示的问题,"雪龙2"号科考破冰船进行了有效的探索。船载实验室采用KVM OVER IP(KVM为Keyboard、Video、Mouse的缩写,数字式多计算机切换器,简称IP KVM)和DVCS(Distributed Video Control System,分布式控制系统,简称DVCS)技术,将科考仪器主机和视频显示系统通过网络连接在一起,实现了在科考船其他位置操作科考仪器主机,同时将需要远程显示的视频数据传输到需要的屏幕上。经过在极地现场的实际应用,两套系统操作方便、系统稳定、视频清晰、维护简单,为现场作业的科考队员提供了便利条件,也得到了科考队员的认可。
