The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform

M Ghanbari - One of the best experts on this subject based on the ideXlab platform.

  • a frequency domain video transcoder for dynamic Bit Rate Reduction of mpeg 2 Bit streams
    IEEE Transactions on Circuits and Systems for Video Technology, 1998
    Co-Authors: Pedro Assuncao, M Ghanbari
    Abstract:

    Many of the forthcoming video services and multimedia applications are expected to use preencoded video for storage and transmission. Video transcoding is intended to provide transmission flexibility to preencoded Bit streams by dynamically adjusting the Bit Rate of these Bit streams according to new bandwidth constraints that were unknown at the time of encoding. In this paper, we propose a drift-free MPEG-2 video transcoder, working entirely in the frequency domain. The various modes of motion compensation (MC) defined in MPEG-2 are implemented in the discrete cosine transform (DCT) domain at reduced computational complexity. By using approximate matrices to compute the MC-DCT blocks, we show that computational complexity can be reduced by 81% compared with the pixel domain approach. Moreover, by using a Lagrangian Rate-distortion optimization for Bit reallocation, we show that optimal transcoding of high-quality Bit streams can produce better picture quality than that obtained by directly encoding the uncompressed video at the same Bit Rates using a nonoptimized Test Model 5 (TM5) encoder.

  • Rate Reduction techniques for mpeg 2 video Bit streams
    Digital Compression Technologies and Systems for Video Communications, 1996
    Co-Authors: Pedro Assuncao, M Ghanbari
    Abstract:

    Rate control is usually an intrinsic function of the video coding algorithm, responsible for matching the available bandwidth of the communication channel to the output Bit stream. However, many of the forthcoming video services will use pre-encoded video, in compressed format, for storage and transmission purposes. In this case, the Rate control function should work on the compressed Bit stream by reducing its Bit Rate according to the network demand, which can be either static or dynamic. Bit Rate Reduction of compressed video is needed not only when pre-encoded video is transmitted, but also in video multicasting where several users receive the same Bit stream through different channels. A similar problem results from the interactivity with the user in video on demand services, where each user is offered the possibility of choosing the amount of bandwidth assigned to its channel. In this paper we analyze Rate Reduction techniques for compressed video in terms of complexity and final picture quality. We propose a new scheme, working entirely in the frequency domain, for Bit Rate Reduction of compressed video. It is a low delay and drift free video transcoder that outperforms a re-encoding system and performs very close to a normal encoder using uncompressed video.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Y Takishima - One of the best experts on this subject based on the ideXlab platform.

  • high speed aac Bit Rate Reduction on the compressed domain
    International Conference on Multimedia and Expo, 2007
    Co-Authors: K Takag, S Miyaji, Y Takishima
    Abstract:

    This paper proposes a high speed Bit Rate Reduction technique on the compressed domain for AAC audio. There are many kinds of AAC audio devices such as PCs and mobile terminals. In order to adapt to various requirements on audio quality and storage capacity, a fast audio transcoding method from a higher to a lower Bit Rate would be beneficial for the efficient use of master AAC contents. Although the scalability function of AAC or baseband transcoding, which converts a Bitstream by decoding and re-encoding, can be employed for this purpose, lower coding efficiency or higher computation load is induced. To resolve these problems, this paper derives the relationship among MDCT, quantization and scaling, and achieves a fast and high quality Bit Rate Reduction by introducing (1) an adaptive scalefactor control, (2) MDCT gain control and 3) the reuse of side information. Experimental results show that the proposed method is about 1.4 times faster than baseband transcoding while achieving almost the equivalent quality.

Pedro Assuncao - One of the best experts on this subject based on the ideXlab platform.

  • a frequency domain video transcoder for dynamic Bit Rate Reduction of mpeg 2 Bit streams
    IEEE Transactions on Circuits and Systems for Video Technology, 1998
    Co-Authors: Pedro Assuncao, M Ghanbari
    Abstract:

    Many of the forthcoming video services and multimedia applications are expected to use preencoded video for storage and transmission. Video transcoding is intended to provide transmission flexibility to preencoded Bit streams by dynamically adjusting the Bit Rate of these Bit streams according to new bandwidth constraints that were unknown at the time of encoding. In this paper, we propose a drift-free MPEG-2 video transcoder, working entirely in the frequency domain. The various modes of motion compensation (MC) defined in MPEG-2 are implemented in the discrete cosine transform (DCT) domain at reduced computational complexity. By using approximate matrices to compute the MC-DCT blocks, we show that computational complexity can be reduced by 81% compared with the pixel domain approach. Moreover, by using a Lagrangian Rate-distortion optimization for Bit reallocation, we show that optimal transcoding of high-quality Bit streams can produce better picture quality than that obtained by directly encoding the uncompressed video at the same Bit Rates using a nonoptimized Test Model 5 (TM5) encoder.

  • Rate Reduction techniques for mpeg 2 video Bit streams
    Digital Compression Technologies and Systems for Video Communications, 1996
    Co-Authors: Pedro Assuncao, M Ghanbari
    Abstract:

    Rate control is usually an intrinsic function of the video coding algorithm, responsible for matching the available bandwidth of the communication channel to the output Bit stream. However, many of the forthcoming video services will use pre-encoded video, in compressed format, for storage and transmission purposes. In this case, the Rate control function should work on the compressed Bit stream by reducing its Bit Rate according to the network demand, which can be either static or dynamic. Bit Rate Reduction of compressed video is needed not only when pre-encoded video is transmitted, but also in video multicasting where several users receive the same Bit stream through different channels. A similar problem results from the interactivity with the user in video on demand services, where each user is offered the possibility of choosing the amount of bandwidth assigned to its channel. In this paper we analyze Rate Reduction techniques for compressed video in terms of complexity and final picture quality. We propose a new scheme, working entirely in the frequency domain, for Bit Rate Reduction of compressed video. It is a low delay and drift free video transcoder that outperforms a re-encoding system and performs very close to a normal encoder using uncompressed video.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Harinath Garudadri - One of the best experts on this subject based on the ideXlab platform.

  • temporal masking for Bit Rate Reduction in audio codec based on frequency domain linear prediction
    International Conference on Acoustics Speech and Signal Processing, 2008
    Co-Authors: Sriram Ganapathy, Petr Motlicek, Hynek Hermansky, Harinath Garudadri
    Abstract:

    Audio coding based on frequency domain linear prediction (FDLP) uses auto-regressive model to approximate Hilbert envelopes in frequency sub-bands for relatively long temporal segments. Although the basic technique achieves good quality of the reconstructed signal, there is a need for improving the coding efficiency. In this paper, we present a novel method for the application of temporal masking to reduce the Bit-Rate in a FDLP based codec. Temporal masking refers to the hearing phenomenon, where the exposure to a sound reduces response to following sounds for a certain period of time (up to 200 ms). In the proposed version of the codec, a first order forward masking model of the human ear is implemented and informal listening experiments using additive white noise are performed to obtain the exact noise masking thresholds. Subsequently, this masking model is employed in encoding the sub- band FDLP carrier signal. Application of the temporal masking in the FDLP codec results in a Bit-Rate Reduction of about 10% without degrading the quality. Performance evaluation is done with perceptual evaluation of audio quality (PEAQ) scores and with subjective listening tests.

M Stroppiana - One of the best experts on this subject based on the ideXlab platform.

  • implementation and performance of an hdtv codec based on the dct
    International Symposium on Circuits and Systems, 1991
    Co-Authors: Marzio Barbero, S Cucchi, M Stroppiana
    Abstract:

    The information provided by M. Barbero et al. (Proc. ISCAS '90, pp 1887-90') on the codecs developed in the framework of the European Project Eureka EU 256 is updated. The system for video compression is based on the hybrid DCT (discrete cosine transform) and the entropy encoding of coefficients. Most characteristics of the coding system coincide with those of the codecs for transmission of 4:2:2 signals, with contribution quality being standardized by ETSI and CMTT. Both conventional-definition TV and high-definition TV (HDTV) codecs have been developed and demonstRated; field trials using HDTV signals were performed. New versions of the codec adopting motion evaluation and compensation, are available. An evaluation of the present system is given, and future perspectives on Bit-Rate Reduction systems are analyzed. >

  • a Bit Rate Reduction system for hdtv transmission
    IEEE Transactions on Circuits and Systems for Video Technology, 1991
    Co-Authors: M Barbero, S Cucchi, M Stroppiana
    Abstract:

    The transmission of HDTV (high-definition television) signals on available digital networks and satellites requires the adoption of sophisticated compression techniques to limit the Bit-Rate requirements and to provide a high-quality and reliable service. A hybrid predictive/transform system has been devised and implemented. The main parameters of this system are in accordance with those being recommended by CMTT for the transmission of conventional component TV. The basic algorithms, the codec architecture, the developed VLSI, and the equipment are described. The codec is designed to opeRate with the currently envisaged TV and HDTV formats and with a wide range of transmission Rates. The optimization of the system and the evaluation of its performance have been carried out on the basis of a large number of subjective tests in accordance with the user requirements specified by the standardization bodies. The codecs have been extensively tested on-field during experimental point-to-multipoint satellite transmission of HDTV signals. >