Efficient downscaling in a transcoder is important when the output video should be converted to a lower resolution video. In this paper, we present a fast MPEG-4 Simple Profile (SP) to H.264 transcoder with reducing s...
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ISBN:
(纸本)9780769529837
Efficient downscaling in a transcoder is important when the output video should be converted to a lower resolution video. In this paper, we present a fast MPEG-4 Simple Profile (SP) to H.264 transcoder with reducing spatial resolution from CIF to QCIF video format. Based on frame image characteristics and motion information in MPEG-4 decoder, we limit motion modes, generate prediction motion vectors and build an adaptive search range for motion estimation in H.264 encoder. Simulation results show that our transcoder reduces transcoding time considerably while video quality is kept almost optimal.
This paper describes a new transcoding algorithm, able to transcode any coded (***-2) bit-stream into an H.264 sequence with arbitrary spatial resolution change. The visual quality at a given input and output bit-rate...
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ISBN:
(纸本)9781424412358
This paper describes a new transcoding algorithm, able to transcode any coded (***-2) bit-stream into an H.264 sequence with arbitrary spatial resolution change. The visual quality at a given input and output bit-rate is close or equal to full decoding followed by a full encoding (0.5 dB-to-2 dB less in PSNR than that of reencoding the stream at the target resolution) while, from the complexity point of view, the proposed transcoding approach is at least ten times faster than re-encoding. The experimental results show that this H.264 transcoder always gives about 20 to 60 % better compression than that of the size of the original MPEG2 sequence scaled by the target resolution ratio at equal subjective quality. Using constant quantization parameters both in the transcoding and re-encoding, transcoding gives 20 to 40 % lesser compression than re-encoding.
In this paper, we propose a speech coding translation scheme by transferring coding parameters between GSM half rate and G.729 coders. Compared to the conventional decode-then-encode (DTE) scheme, the proposed paramet...
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In this paper, we propose a speech coding translation scheme by transferring coding parameters between GSM half rate and G.729 coders. Compared to the conventional decode-then-encode (DTE) scheme, the proposed parameter conversions provide speech interoperability between mobile and IP networks with reducing computational complexity and coding delay. Simulation results show that the proposed methods can reduce about 30% computational load and coding delay acquired in the target encoders and achieve almost imperceptible degradation in performance.
The use of applications related to real-time video communications is spreading. But it is becoming difficult to secure the bandwidth, because of the increase in the number of the users as well as the bandwidth require...
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The use of applications related to real-time video communications is spreading. But it is becoming difficult to secure the bandwidth, because of the increase in the number of the users as well as the bandwidth requirements of each user. In this context, a transcoder that can recode the video data to a usable bit rate for transmission is needed. In order to maintain as high a quality of service as possible, as seen by the user, there must be a criterion for assessment of image quality, by which the amounts of video information in the space and time directions can be reduced with good balance. In the conventional transcoder, control is based mostly on the square error, but it is not always true that the square error can directly represent the video quality seen or subjectively perceived by the user (subjective assessment quality). Consequently, this paper proposes a method of estimating the frame rate (optimal frame rate) that maximizes the subjective assessment quality in the recoding of video data (original data) stored in a video server to a specified bit rate. In the proposed method, the mean opinion score (MOS) obtained by a large number of subjective assessment tests is approximated by a function containing a small number of parameters, and the parameters of the function are estimated on the basis of the features of the original image. By specifying the bit rate for the function, the optimal frame rate is determined by determining the maximum. Interval estimation of the optimal frame rate was performed by applying the proposed method to open data, and it was verified that the frame rate could be estimated with a mean error of approximately 4 frames/s. (C) 2003 Wiley Periodicals, Inc.
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