In the context of a Call for Proposal for integer IDCTs issued by MPEG in July 2005, a full 2D integer IDCT based on a
previous Feig and Winograd's work has been proposed. It achieves a high precision by meeting all IEEE1180 conditions
and is suitable of implementation on hardware since it can be performed only with shifts and additions. Furthermore, it
can be useful in high video resolution scenarios like in 720p/1080i/p due to its feedforward operation mode without any
loop as usual in row-column implementations. The proposed transformation can be implemented without changing other
functional blocks either at the encoder or at the decoder or alternatively as a scaled version incorporating the scaling
factors into the dequantization stage. Our algorithm uses only 1328 operations for 8x8 blocks, including scaling factors.
This paper evaluates the performance of a high frequency (HF) wireless network for transporting packet multimedia services. Beyond of allowing civil/amateur communications, HF bands are also used for long distance wireless military communications. Therefore, our work is based on NATO Link and Physical layer standards, STANAG 5066 and STANAG 4539 respectively. At each HF channel, a typical transmission bandwidth is about 3 kHz with the resulting throughput bit rate up to 12800 bps. This very low bit rate by itself imposes serious challenges for reliable and low delay real time multimedia communications. Thus, this paper discusses the performance of a real time communication system designed to allow an end-to-end communication through “best effort” networks. With HF channel diversity, the packet loss percentage, on average considering three channel conditions, is decreased by 16% in the channel SNR range from 0 to 45 dB.
KEYWORDS: Forward error correction, Quadrature amplitude modulation, Signal to noise ratio, Multimedia, Telecommunications, Modulators, Error control coding, Modulation, High dynamic range imaging, Data communications
The recent rapid growth of multimedia communications has efficiently allowed delivering different services, formats and contents over an enormous variety of digital networks with IP acting as an integration protocol. The main objective of this research work is to evaluate the performance of an high frequency (HF) wireless network for transporting multimedia services according to UDP/IP protocol stack. Besides, allowing civil/amateur communications, HF bands are also used for long distance wireless military communications. Therefore, our work is based on NATO Link and Physical layer standards, STANAG 5066 and STANAG 4539, respectively. A typical transmission bandwidth is about 3 kHz resulting in a varying bit rate in the range between 75 and 12800 bps. This very low bit rate by itself imposes
serious challenges for reliable real time multimedia communications. This paper discusses optimal combinations of channel coders, modulators and packet sizes in order to achieve the greatest throughput in function of the signal-to-noise ratio and HF channel conditions.
Wireless access to encoded video requires sophisticated error resilient mechanisms. Although some video coding standards describe error resilience algorithms, they are inefficient at deep fading wireless and mobile channels. In this paper, we present a novel scheme of error protection for narrowband wireless channels which is independent of any video coding standard. Being, however, this scheme common to all standards, it provides some acceptable video quality degradation. We have evaluated the quality degradation of the Common solution in comparison to the optimal scheme of protection corresponding to the existence of a finite number of channel codes. Besides, we also present the quality degradation for both video coding standards, H.263 and MPEG-4, obtained from a finite number of codes in comparison with the ideal scheme corresponding to the existence of an infinite number of channel codes. Additionally, we proposed a protection solution tailored to H.263/MPEG-4 source coding with an average PSNR improvement of about 0.2 dB relatively to the above mentioned Common solution. Thus, in the framework of joint source-channel coding, we present an adaptive scheme of protection according to the channel bit error rate (BER) and with an overall transmission rate of 64 kbps. In our investigation, we used four QCIF video test sequences and rate compatible punctured convolutional (RCPC) codes. For instance, a PSNR gain of about 16.7 dB is obtained at BER=10-2 for 'Foreman' video sequence, encoded either by H.263 or by MPEG-4 and protected using the Common scheme in comparison to the unprotected case.
KEYWORDS: Video, Signal to noise ratio, Standards development, Video coding, Error analysis, Binary data, Image quality standards, Visualization, Video compression, Scalable video coding
This paper considers the transmission of QCIF resolution MPEG-4 video signals over hostile channels like wireless and mobile at transmission rate of 64 kbps. Although MPEG-4 incorporates some error resilience tools, this standard is still fragile for video transmission over time-variant deep fading channels. We investigated the significance of MPEG-4 video syntactical elements considering MPEG-4 encoded streams, QPSK modulated and delivered through Binary, AWGN and Rayleigh (50 Km/h) channels with SNR range between 0 and 40 dB. We have used four QCIF video test sequences, Foreman, News, Container and Coastguard, and enabled slice resynchronization and data partitioning modes in MPEG-4 video coding. The simulation results show that despite significance of particular elements varies with the channel SNR and with the particular test sequence, we could graphically identify two classes of significance at low channel SNRs. The most significant class includes elements such as VOP header, Video Packet header, DC Marker and DC Coefficients of INTRA-VOP & MB header. At high Rayleigh channel SNR, above 15 dB, AC coefficients of INTRA-VOPs and Motion Vectors were found to be the most significant elements. Any unequal error protection, data partitioning and grouping strategies covering a wide range of SNRs can then be designed based on the significance results presented in this paper.
The purpose of our work is to report a solution for the problem of the Joint Source-Channel Coding (JSCC) of the H.263 bit stream to be transmitted through error prone channels. Our investigations led us to classify the H.263 syntactical elements into several classes of different significance. By identifying the most sensitive elements we developed a data partitioning (DP) technique which exhibits improved error resilience. A good reconstructed video quality is obtained for a constant 64 kbit/s transmission rate using Rate Compatible Punctured Convolutional (RCPC) codes of different rates for forward error protection. By exploiting the different syntactical element sensitivities we presented an Unequal Error Protection (UEP) scheme that surpasses the optimal Equal Error Protection (EEP). The forward error correction adopted has resulted in PSNR improvements over 20 dB for bit error rates higher than of 4 X 10-3.
Generally speaking, a recognition system should be insensitive to translation, rotation, scaling and distortion found in the data set. Non-linear distortion is difficult to eliminate. This paper discusses a method based on dynamic programming which copes with features normalization subjected to small non-linear distortions. Combining with k- means clustering results in a statistical classification algorithm suitable for pattern recognition problems. In order to assess the classifier, it has been integrated into a hand-written character recognition system. Dynamic features have been extracted from a database of 1248 isolated Roman character. The recognition rates are, on average, 91.67 percent and 94.55 percent. The classifier might also be tailored to any pattern recognition application.
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