A fast macroblock mode decision scheme is proposed in this work for arbitrary downsizing video transcoder based on H.264/AVC. For macroblock to be re-encoded in downsized frame, the corresponding area in the pre-encod...
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ISBN:
(纸本)9781479979813
A fast macroblock mode decision scheme is proposed in this work for arbitrary downsizing video transcoder based on H.264/AVC. For macroblock to be re-encoded in downsized frame, the corresponding area in the pre-encoded frame is not aligned with the boundary of blocks when downsizing factor is arbitrary. The concepts of 'mapped block' and 'overlapped block' are proposed in this paper to represent the corresponding area. To reduce the computational complexity, method based on blocks or based on pixels is adopted according to the value of downsizing factor. We compared the compression performance and computational complexity of the proposed method with the full mode search method. The proposal can significantly reduce the computational complexity while the compression performance loss is slight.
In video transcoding, accuracy and efficiency of macroblock mode decision are critical issues at the re-encoder side due to the changes in frame size, frame rate, and bit rate. In this paper, a fast macroblock mode de...
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In video transcoding, accuracy and efficiency of macroblock mode decision are critical issues at the re-encoder side due to the changes in frame size, frame rate, and bit rate. In this paper, a fast macroblock mode decision scheme based on support vector machines is proposed for H.264/AVC baseline profile video transcoder. Features including motion vectors, residual data, pre-encoded macroblock modes, and quantization parameters are extracted from incoming bitstream in both of training stage and classification stage. Feature extraction methods are investigated for spatial resolution transcoder, temporal resolution transcoder, and bit-rate transcoder. After off-line training and simplification of support vectors, the obtained support vector machine classifier can determine macroblock mode in the re-encoder accurately. Extensive experiments are carried out on different types of transcoders and results show that the proposed method can save about 80% in computational complexity compared to full mode search algorithm implemented in the latest H.264/AVC reference software (JM17.1), while maximum peak signal-to-noise ratio is degraded by 0.2-1.1 dB depending on different sequences and bit rate.
In this paper, a new bit rate estimation scheme is proposed to determine the bit rate for each subclass in an MPEG-2 TS to H. 264/AVC transcoder after dividing an input MPEG-2 TS sequence into several subclasses. Vide...
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In this paper, a new bit rate estimation scheme is proposed to determine the bit rate for each subclass in an MPEG-2 TS to H. 264/AVC transcoder after dividing an input MPEG-2 TS sequence into several subclasses. video format transcoding in conventional IPTV and Smart TV services is a time-consuming process since the input sequence should be fully transcoded several times with different bit-rates to decide the bit-rate suitable for a service. The proposed scheme can automatically decide the bit-rate for the transcoded video sequence in those services which can be stored on a video streaming server as small as possible without losing any subject quality loss. In the proposed scheme, an input sequence to the transcoder is sub-classified by hierarchical clustering using a parameter value extracted from each frame. The candidate frames of each subclass are used to estimate the bit rate using a statistical analysis and a mathematical model. Experimental results show that the proposed scheme reduces the bit rate by, on an average approximately 52% in low-complexity video and 6% in high-complexity video with negligible degradation in subjective quality.
An intra mode selection scheme is proposed in this work, which supports both downsizing transcoding and re-quantization transcoding simultaneously. In the proposal, a total number of nonzero coefficients in precoded f...
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An intra mode selection scheme is proposed in this work, which supports both downsizing transcoding and re-quantization transcoding simultaneously. In the proposal, a total number of nonzero coefficients in precoded frame is used as criterion and a thresholding method is applied to select intra macroblock mode in re-encoder. To calculate this threshold, which is related to re-quantization parameter (denoted as Q(r)), we propose a Th_I-Q(r) model which includes direct method and percentage I16MB method. In the former, an exponent model is proposed to describe relationship between the threshold and the Q(r);while in the latter, the threshold Th_I is converted into percentage of macroblocks with I16MB mode in the downsized frame (denoted as per 16), and relationship between the per_16 and the Q(r) is also modeled as an exponent function. Then the two exponent models are all converted into linear regression model, and least square estimation is used to estimate the parameters of the models. Furthermore, if I4MB mode is selected for one macroblock, the intra prediction modes in precoded frame are utilized to select prediction mode for every 4 x 4 block of the macroblock in downsized frame to reduce computational complexity. We compared rate distortion performance and computational complexity of the proposed method with rate-distortion optimization method. Simulation results demonstrate that on the precondition of compression performance of the proposal being close to the results of the rate-distortion optimization method, the proposed method can save up to 30 and 80% in total encoding time and mode decision time, respectively. (C) 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 340-349, 2009;Published online in Wiley InterScience (***. com). DOI 10.1002/ima.20211
The main design criterion of efficient transcoding system is to utilize the information embedded in coded bitstream to reduce the computational complexity of the transcoding. H.264 encoder spends significant time and ...
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ISBN:
(纸本)9781424448586
The main design criterion of efficient transcoding system is to utilize the information embedded in coded bitstream to reduce the computational complexity of the transcoding. H.264 encoder spends significant time and computations to determine the best encoding mode for a Macroblock (MB) encoding mode. We propose to use MB encoding mode and residue statistics of MPEG-2 coded bitstream to decide on the best MB partition mode for H.264 encoding. Performance evaluations have shown that for similar objective and subjective quality, our proposed scheme can reduce the computational complexity to half as compared to the full decode-encode system, while transcoding at half the bitrate as compared to the MPEG-2 bitrate.
This paper proposes a video transcoder that realizes efficiently the function of multirate conversion to multiple bitrates. The multirate conversion function is realized as follows. The decoder and the inverse quantiz...
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This paper proposes a video transcoder that realizes efficiently the function of multirate conversion to multiple bitrates. The multirate conversion function is realized as follows. The decoder and the inverse quantizer are shared as a single processor. The requantizer and the reencoder with the same requantization step are shared among outputs. With these provisions, an architecture is proposed whereby the processing complexity in multirate conversion can be reduced. The number of requantization processing operations per macro-block is examined theoretically, and it is shown that the conversion processing complexity can be formulated as a function of the output bitrate. Lastly, the theoretical evaluation and the evaluation experiment based on these investigations show that the sharing of the requantizer/reencoder is the scheme that reduces the increase of the processing complexity as a function of the number of outputs, and can cope with any number of outputs with two to four times the processing complexity of the single-rate output scheme. (C) 2004 Wiley Periodicals, Inc.
In transmission of bursty traffic such as video and data, a network with a fu;ed capacity may have some unused bandwidth. The available bit rate (ABR) scheme in ATM networks can make use of this spare channel capacity...
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In transmission of bursty traffic such as video and data, a network with a fu;ed capacity may have some unused bandwidth. The available bit rate (ABR) scheme in ATM networks can make use of this spare channel capacity as a lower priority service. ABR has been developed initially for delay-tolerant services such as data. The authors demonstrate how, with the help of a video transcoder, delay-sensitive services such as video may be transmitted over ABR. The transcoder further compresses the video bit stream according to the rates dictated by the network with minimum degradation to the picture quality. The video quality has been optimised by combining the classical minimum cell rate (MCR) with the subjectively acceptable minimum quality (SAMQ). The performance of two different coding formats for ABR sources, namely the constant bit rate (CBR) and variable bit rate (VBR) video input to the transcoder are compared. The authors also present techniques for further reduction of congestion at the multiplexing switches and report on the impact of the forward and backward link delays on the ABR performance with a video transcoder.
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