In this paper, QOS Control of realtime multimedia communication system under heterogeneous environment by the wired and the wireless networks is proposed. In our suggested system, as channel coding, FEC (forward Error...
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ISBN:
(纸本)0769515886
In this paper, QOS Control of realtime multimedia communication system under heterogeneous environment by the wired and the wireless networks is proposed. In our suggested system, as channel coding, FEC (forward Error Correction) method with Reed-Solomon coding is introduced to reduce the packet error rate on the wireless network. On the other hand, as source coding, transcoding methods including transformation of various video codings such as M-JPEG, MPEG and Quicktime, controls of Q-factor within a frame, frame rate and color depth is introduced to maintain the required QOS, particularly the end-to-end throughput. The increases of the required bandwidth by redundant packet addition with FEC can be suppressed by the transcoding functions while the packet error rate is reduced to the accepted value. In order to verify the functionality and the efficiency in our suggested system, numerical simulation was held. As the result, out suggested system by combination of transcoding and FEC could correct the packet error rate with an order of 10(9) while maintaining the frame rate and the amount of data transform at a constant.
Video transmission on the Internet often requires a transcoding in order for the bitrate to meet the available bandwidth. Since the bitrate of videos is determined by an amount of bits per frame(BPF) and framerate(FPS...
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ISBN:
(纸本)0819444111
Video transmission on the Internet often requires a transcoding in order for the bitrate to meet the available bandwidth. Since the bitrate of videos is determined by an amount of bits per frame(BPF) and framerate(FPS), one of or either of these should be reduced in transcoding. In addition, because there is a tradeoff between the BPF and FPS under a bitrate constraint, the BPF and FPS should be optimally determined to get the best subjective video quality. This paper proposes a framerate optimization method, which estimates an optimal framerate directly from a target video and a specified bitrate. Actually, an optimal framerate is derived by using a characteristic surface of Mean Opinion Score(MOS), which is estimated by suitable features of a target video. Comparison of the optimal framerate obtained by the actual measurement with one by the proposed technique has proved that the accuracy of estimation by the proposed technique is satisfactory for several open data sequences.
In this paper, transcoding of pre-encoded MPEG-1,2 video into lower bit rates is realized through altering the coding algorithm into H.261/H.263 standards with lower spatial resolutions. We extract and compose a set o...
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In this paper, transcoding of pre-encoded MPEG-1,2 video into lower bit rates is realized through altering the coding algorithm into H.261/H.263 standards with lower spatial resolutions. We extract and compose a set of candidate motion vectors, from the incoming bit stream, to comply with the encoding format of the output bit stream. For the spatial resolution reduction, we generate one motion vector out of a set of input motion vectors operating on the higher spatial resolution image. We discuss the impact of motion estimation refinement on the new motion vectors and show that for all cases a simple half-pixel refinement is sufficient for near-optimum results.
In most of the current image/video compression standard, such as JPEG, MPEG, H.263, etc, the DCT is used. The DCT coefficients for every AC frequency component usually have Laplacian distribution. Such a distribution ...
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In most of the current image/video compression standard, such as JPEG, MPEG, H.263, etc, the DCT is used. The DCT coefficients for every AC frequency component usually have Laplacian distribution. Such a distribution is critical in the image or video transcoding system. Therefore, the parameter in the distribution should be well estimated. Different from the normal parameter estimation, in the transcoding system, the original DCT value is unavailable, and only the dequantized value is available. In this paper, we propose 3 estimation methods based on the dequantized value for the transcoding system. The simulation demonstrates that they can yield very good results. In addition, under a fixed bit rate, they can work even better than estimation with the original DCT value in the sense of image/frame's PSNR.
This paper describes a low complexity MPEG-2 bitrate transcoding algorithm that achieves an extra compression factor of about two without introducing annoying coding artefacts. Due to the low complexity of this algori...
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This paper describes a low complexity MPEG-2 bitrate transcoding algorithm that achieves an extra compression factor of about two without introducing annoying coding artefacts. Due to the low complexity of this algorithm it is especially applicable in DSP/CPU software solutions or in consumer applications that require high throughput.
In various networked multimedia applications, it is often necessary to change the bit-rate and format of a pre-encoded bit-stream. This can be achieved using a cascaded pixel-domain transcoder, which fully decodes an ...
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ISBN:
(纸本)0780354826
In various networked multimedia applications, it is often necessary to change the bit-rate and format of a pre-encoded bit-stream. This can be achieved using a cascaded pixel-domain transcoder, which fully decodes an incoming bit-stream and then re-encodes the decoded pictures with the desired bit-rate or format. However, the cascaded pixel-domain transcoder is computationally expensive. To reduce the computations, several fast architectures have been proposed in the literature. However, these fast transcoder architectures introduce new limitations and are not drift-free. In this paper, we propose new techniques to implement a fast cascaded pixel-domain transcoder. We further discuss the limitation and speed of the different transcoder architectures. We also discuss the methods for adding watermark or company logo, using the different transcoder architectures.
This paper addresses the bit-rate reduction of MPEG-2 compressed video and presents a method to reduce requantization errors in transcoding. The proposed method assumes Laplacian distributions for the original AC coef...
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ISBN:
(纸本)0780362977
This paper addresses the bit-rate reduction of MPEG-2 compressed video and presents a method to reduce requantization errors in transcoding. The proposed method assumes Laplacian distributions for the original AC coefficients of the DCT. A Laplacian parameter for each coefficient is estimated at the transcoder from the quantized input DCT coefficients. These parameters are then used in requantization to improve the quality of the transcoded video. The algorithm provided in this paper to estimate the Laplacian parameters of the original DCT coefficients is simple to implement and may be adapted to other DCT-based coding schemes.
In this paper, we focus on the methods for delivering object-based video data. More specifically, me exploit the fact that a finer level of scalability can be achieved when the video frame has been decomposed into obj...
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In this paper, we focus on the methods for delivering object-based video data. More specifically, me exploit the fact that a finer level of scalability can be achieved when the video frame has been decomposed into objects and coded using MPEG-4. A new framework is proposed.
In network delivery of digital video, if the bandwidth required for a video is not available, the video has to be recoded at a reduced bit rate. It is highly desirable that the transcoding is carried out in real time ...
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ISBN:
(纸本)0780362977
In network delivery of digital video, if the bandwidth required for a video is not available, the video has to be recoded at a reduced bit rate. It is highly desirable that the transcoding is carried out in real time while maintaining reasonable image quality. In this paper, we propose a fast approach to derive from an MPEG stream a new MPEG stream with half the spatial resolution. For the downsized video, we first generate from the original compressed video an improved estimate of the motion vectors. We then propose a compressed domain approach with data hiding to produce DCT residues by an open-loop method. The computational complexity is significantly lower than a number of previous approaches. Simulation suggests that our approach produces reasonable image quality.
A macroblock-based optimization method is described for selecting quantization parameters so as to reduce the re-quantization errors in MPEG transcoding. Analysis has shown that re-quantization using a parameter large...
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ISBN:
(纸本)0780362977
A macroblock-based optimization method is described for selecting quantization parameters so as to reduce the re-quantization errors in MPEG transcoding. Analysis has shown that re-quantization using a parameter larger than the original input quantization parameter but smaller than twice the original causes significant information loss in transcoding. This problem can be avoided by using a parameter larger than twice the original. The optimization method was thus extended based on a rate-distortion model to enable the re-quantization parameter to be selected from ones larger than twice the original input quantization range. This improved method outperformed a typical non-optimized transcoding scheme, improving the PSNR by about 1 dB.
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