共查询到20条相似文献,搜索用时 31 毫秒
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Jeongnam Youn Ming-Ting Sun 《Journal of Visual Communication and Image Representation》2000,11(4):385-403
Video transcoding is one of the key technologies in implementing dynamic adaptation of the bit-rate of a coded video bit-stream to the available bandwidth over various networks. Many fast transcoder architectures have been proposed to achieve fast processing. However, they suffer from quality degradation caused by the drift error. In this paper, we investigate the drift caused by the fast transcoder architectures for transcoding H.263 bit-streams. We discuss the limitations of the fast transcoder architectures and the flexibility that can be offered by a cascaded pixel-domain transcoder. Since the cascaded pixel-domain transcoder can achieve drift-free performance, we also propose methods to reduce the computational complexity of the drift-free cascaded pixel-domain transcoder. 相似文献
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We propose a fast arbitrary-ratio image resizing method for transcoding of the compressed images. The downsizing process in the discrete cosine transform (DCT) domain can be implemented by truncating high-frequency coefficients, whereas the upsizing process is implemented in the DCT domain by padding zero coefficients to the high-frequency part. The proposed method combines a fast inverse and forward DCT of composite length for arbitrary-ratio upsizing or downsizing. According to the resizing ratio, truncating the high-frequency coefficients and padding zeros are appropriately considered by combining the inverse DCT and forward DCT. The proposed method shows a good peak signal-to-noise ratio and less computational complexity compared with the spatial-domain and previous DCT-domain image resizing methods. 相似文献
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Jing Zhang Anthony T. S. Ho Gang Qiu Pina Marziliano 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2007,54(2):205-209
A robust video watermarking scheme of the state-of-the-art video coding standard H.264/AVC is proposed in this brief. 2-D 8-bit watermarks such as detailed company trademarks or logos can be used as inconvertible watermark for copyright protection. A grayscale watermark pattern is first modified to accommodate the H.264/AVC computational constraints, and then embedded into video data in the compressed domain. With the proposed method, the video watermarking scheme can achieve high robustness and good visual quality without increasing the overall bit-rate. Experimental results show that our algorithm can robustly survive transcoding process and strong common signal processing attacks, such as bit-rate reduction, Gaussian filtering and contrast enhancement 相似文献
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《Signal Processing: Image Communication》2006,21(1):44-58
To achieve portability between different kinds of encoding formats and network environments, heterogeneous video transcoding becomes a key technique for reducing the bitrate of a previously compressed video signal. A frame-skipping transcoder is often used to avoid an unacceptable picture quality when high transcoding ratio is required. Due to high computational complexity and quality degradation introduced by conventional frame-skipping transcoders, a DCT-based video frame-skipping transcoder has been proposed recently. However, the transcoding process of the motion compensated macroblocks in the DCT domain becomes the bottleneck since IDCT and DCT processes are required. In this paper, we propose a new architecture of the frame-skipping transcoder to reduce the computational complexity of motion compensated macroblocks in the frame-skipping process. The new architecture transcodes the dominant region of a motion compensated macroblock in the DCT domain by making use of the DCT coefficients of the incoming bistream and some pre-computed shift operators. By using a shifted version of the dominant vector, the re-encoding error introduced in the dominant region can be avoided. On the other hand, an adaptive transcoding architecture to transcode the boundary regions of MC marcoblocks and a way to perform error compensation are proposed. This architecture can further speed up the transcoding process of the motion compensated macroblocks. Half pixel accuracy related to our proposed frame skipping transcoder is also addressed. Experimental results show that, as compared to the conventional or DCT-based transocders, the new architecture is more robust to noise, gives rise to fewer requantization errors, and requires simple computational complexity. 相似文献
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The way computing was done has changed a lot in recent times. Nowadays mobile devices have been the stealing the show. These devices come in different specifications, that any multimedia content that is to be played requires transcoding for better user experiences. Cloud based video services cater to the needs of the end user based on their requirements, through video transcoding. Hence video transcoding plays a very important role in today’s evolving streaming media environment. The major problem with video transcoding is that it consumes a lot of time and impacts seriously on the quality of the output. Transcoding uses the device information to transform the video into the required format and this process is done in a distributed fashion, to speed up the process. This work proposes an Intelligent Video Splitter which uses the Map Reduce algorithm to provide efficiency based on time factor. The important performance metrics including video distortion (VD), video distortion due to frame dependency (FDD) were considered. The results showed that the proposed framework perceptibly outperforms than the prevailing strategies. It provides higher video quality as a result of it introduces less video distortion. In future this method may be extended to supply associate automatic device aware video standards. 相似文献
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A fast method to reduce the computational complexity of a frequency domain transcoder for bit-rate reduction of compressed video bit streams is proposed. The proposed method reduces the computational complexity of a pixel domain transcoder by 81.25% while the introduced distortion in the transcoded pictures is 0.2 dB 相似文献
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Video transcoding architectures and techniques: an overview 总被引:2,自引:0,他引:2
Throughout this article, we concentrate on the transcoding of block-based video coding schemes that use hybrid discrete cosine transform (DCT) and motion compensation (MC). In such schemes, the frames of the video sequence are divided into macroblocks (MBs), where each MB typically consists of a luminance block (e.g., of size 16 /spl times/ 16, or alternatively, four 8 /spl times/ 8 blocks) along with corresponding chrominance blocks (e.g., 8 /spl times/ 8 Cb and 8 /spl times/ 8 Cr). This article emphasizes the processing that is done on the luminance components of the video. In general, the chrominance components can be handled similarly and will not be discussed in this article. We first provide an overview of the techniques used for bit-rate reduction and the corresponding architectures that have been proposed. Then, we describe the advances regarding spatial and temporal resolution reduction techniques and architectures. Additionally, an overview of error resilient transcoding is also provided, as well as a discussion of scalable coding techniques and how they relate to video transcoding. Finally, the article ends with concluding remarks, including pointers to other works on video transcoding that have not been covered in this article, as well as some future directions. 相似文献
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《Broadcasting, IEEE Transactions on》2009,55(4):767-775
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The latest international video-coding standard H.264/AVC significantly achieves better coding performance compared to prior
video coding standards such as MPEG-2 and H.263, which have been widely used in today’s digital video applications. To provide
the interoperability between different coding standards, this paper proposes an efficient architecture for MPEG-2/H.263/H.264/AVC
to H.264/AVC intra frame transcoding, using the original information such as discrete cosine transform (DCT) coefficients
and coded mode type. Low-frequency components of DCT coefficients and a novel rate distortion cost function are used to select
a set of candidate modes for rate distortion optimization (RDO) decision. For H.263 and H.264/AVC, a mode refinement scheme
is utilized to eliminate unlikely modes before RDO mode decision, based on coded mode information. The experimental results,
conducted on JM12.2 with fast C8MB mode decision, reveal that average 58%, 59% and 60% of computation (re-encoding) time can
be saved for MPEG-2, H.263, H.264/AVC to H.264/AVC intra frame transcodings respectively, while preserving good coding performance
when compared with complex cascaded pixel domain transcoding (CCPDT); or average 88% (a speed up factor of 8) when compared
with CCPDT without considering fast C8MB. The proposed algorithm for H.264/AVC homogeneous transcoding is also compared to
the simple cascaded pixel domain transcoding (with original mode reuse). The results of this comparison indicate that the
proposed algorithm significantly outperforms the mode reuse algorithm in coding performance, with only slightly higher computation. 相似文献
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A video coding system for applications requiring very low bit-rate is presented. This coding scheme uses an intraframe coder for the initial frame in the video sequence and subsequent frames are coded using an interframe coding method. A wavelet-based technique is used for intraframe coding. For interframe coding, displaced frame differences (DFD) are computed and coded using a segmentation-based method wherein the displaced frame difference is segmented into active and inactive regions using morphological operators. To meet the very low bit-rate requirements, the motion vectors are processed so as to reduce their contribution to the overall bit-rate. To reduce coding artifacts, a post-processing technique is developed for use at the decoder. Coding performance of the proposed coding scheme is evaluated at 16 kbit/s and 32 kbit/s using luminance component of several typical test sequences at QCIF resolution with a frame rate 8.3 frame/s. 相似文献
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Streaming of video, which is both source- and channel-coded, over wireless networks faces the challenge of time-varying packet loss rate and fluctuating bandwidth. Rate shaping (RS) has been proposed to reduce the bit-rate of a precoded video bitstream to adapt to the real-time bandwidth variation. In our earlier work, rate shaping was extended to consider not only the bandwidth but also the packet loss rate variations. Rate-distortion optimized rate adaptation is performed on the precoded video that is a scalable coded bitstream protected by forward error correction codes. In this paper, we propose an RS scheme that further takes into account the error concealment (EC) method used at the receiver. We refer to this scheme as EC aware RS (ECARS). When performing ECARS, first ECARS needs to know the benefit/gain of sending each part of the precoded video, as opposed to not sending it but reconstructing it by EC. Then given a certain packet loss probability, the expected gain can be derived and be included in the rate-distortion optimization problem formulation. Finally, ECARS performs rate-distortion optimization to adapt the rate of the precoded video. A two-stage rate-distortion optimization approach is proposed to solve the ECARS rate-distortion optimization problem. In addition to ECARS, the precoding process can be EC aware to prioritize the precoded video based on the gain. We present an example EC aware precoding process by means of macroblock prioritization. Experiment results of ECARS together with EC aware precoding are shown to have excellent performance. 相似文献
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Shizhong Liu Alan C. Bovik 《Journal of Visual Communication and Image Representation》2005,16(6):643-667
Video transcoding is a key technology to support video communications over heterogeneous networks. Although quite a bit of research effort has been made in video transcoding due to its wide applications, most video transcoding techniques proposed in the literature are optimized based on the simple mean squared error (MSE) metric which does not correlate well with the human visual perception. In this paper, foveation, a property of the HVS, is exploited in video transcoding. The proposed foveation embedded DCT domain video transcoding can reduce the bit rate without compromising visual quality or achieve better subjective quality for a given bit rate by shaping the compression distortion according to the foveated contrast sensitivity function of the HVS. In addition, fast algorithms for video foveation filtering and DCT domain inverse motion compensation are developed, which significantly improve the efficiency of video transcoding. 相似文献
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Bandwidth-constrained real-time conversational video communications (such as mobile teleconferencing) require video codecs with good rate-distortion characteristics at low bit-rates and modest computational complexity. While target-specific object-based and model-based coding methods have been proposed for low bit-rate conversational video coding, difficulties in generalization and high computational complexity hinder their practical utilization. In this paper, we propose a low bit-rate coding method for typical conversational video by combining two-dimensional model-based coding of face regions and object-based coding of non-face head-shoulder regions, achieving high-quality face reconstruction and low overall bit-rate with real-time encoding capability. Experiments on typical conversational test sequences confirm that, compared to other conversational video codecs, our model-and-object-based coding method offers superior rate-distortion performance at low bit-rates. 相似文献
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For a conventional downscaling video transcoder, a video server has firstly to decompress the video, perform downscaling operations in the pixel domain, and then recompress it. This is computationally intensive. However, it is difficult to perform video downscaling in the discrete cosine transform (DCT)- domain since the prediction errors of each frame are computed from its immediate past higher resolution frames. Recently, a fast algorithm for DCT domain image downsampling has been proposed to obtain the downsampled version of DCT coefficients with low computational complexity. However, there is a mismatch between the downsampled version of DCT coefficients and the resampled motion vectors. In other words, significant quality degradation is introduced when the derivation of the original motion vectors and the resampled motion vector is large. In this paper, we propose a new architecture to obtain resampled DCT coefficients in the DCT domain by using the split and merge technique. Using our proposed video transcoder architecture, a macroblock is splitted into two regions: dominant region and the boundary region. The dominant region of the macroblock can be transcoded in the DCT domain with low computational complexity and re-encoding error can be avoided. By transcoding the boundary region adaptively, low computational complexity can also be achieved. More importantly, the re-encoding error introduced in the boundary region can be controlled more dynamically. Experimental results show that our proposed video downscaling transcoder can lead to significant computational savings as well as videos with high quality as compared with the conventional approach. The proposed video transcoder is useful for video servers that provide quality service in real-time for heterogeneous clients. 相似文献
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提出了一个基于MPEG4的快速高效存储的DCT视频编码器,用他把一个H.261视频数据流转换为一个低比特率、低空间分辨率的MPEG4流,并进行无线视频处理。和现有编码器相比,他不仅能够大大地节省实际需要存储空间,计算复杂度也降低了许多,实验结果表明设计的编码器得到的视频质量与象素领域方法得到的视频质量相当。 相似文献