Current Issue : October - December Volume : 2016 Issue Number : 4 Articles : 5 Articles
Recently, HTTP streaming has become very popular for delivering videos over the Internet. For adaptivity, a provider should\ngenerate multiple versions of a video as well as the related metadata. Various adaptation methods have been proposed to support a\nstreaming client in coping with strong bandwidth variations. However, most of existing methods target at constant bitrate (CBR)\nvideos only. In this paper, we present a new method for quality adaptation in on-demand streaming of variable bitrate (VBR) videos.\nTo cope with strong variations of VBR bitrate, we use a local average bitrate as the representative bitrate of a version. A buffer-based\nalgorithm is then proposed to conservatively adapt video quality.Through experiments in the mobile streaming context, we show\nthat our method can provide quality stability as well as buffer stability even under very strong variations of bandwidth and video\nbitrates....
Today, eavesdropping is becoming a common issue in the rapidly growing digital network and has foreseen the need for secret\ncommunication channels embedded in digital media. In this paper, a novel steganography technique designed for Standard\nDefinition Digital Television (SDTV) H.264/AVC encoded video sequences is presented. The algorithm introduced here makes\nuse of the compression properties of the Context Adaptive Variable Length Coding (CAVLC) entropy encoder to achieve a low\ncomplexity and real-time inserting method. The chosen scheme hides the private message directly in the H.264/AVC bit stream\nby modifying the AC frequency quantized residual luminance coefficients of intrapredicted I-frames. In order to avoid error\npropagation in adjacent blocks, an interlaced embedding strategy is applied. Likewise, the steganography technique proposed allows\nself-detection of the hidden message at the target destination.The code source was implemented by mixing MATLAB 2010 b and\nJava development environments. Finally, experimental results have been assessed through objective and subjective quality measures\nand reveal that less visible artifacts are produced with the technique proposed by reaching PSNR values above 40.0 dB and an\nembedding bit rate average per secret communication channel of 425 bits/sec. This exemplifies that steganography is affordable in\ndigital television....
Cognitive radio (CR) systems are designed to utilize the available radio spectrum in an efficient and intelligent manner. Terrestrial\nDigital Video Broadcasting (DVB-T) frequency bands are one of the future candidates for cognitive radio applications especially\nbecause after digital television transition the TV white spaces (TVWS) became available for radio communication. This paper\ndeals with the survey of the DVB-T spectrum; wideband measurements were performed on mobile platform in order to study\nthe variation of the radio signal power in city area aboard a moving vehicle.The measurement environment was a densely built-in\nregionwhere the properDVB-T receiving was guaranteed by three TVtransmitters, utilizing three central channel frequencies using\n610, 746, and 770MHz. In our paper the methods, the applied antenna, and measurement devices will be presented together with\nsimulated andmeasured fading statistics.Thefinal result is an estimation of the cognitive DVB-T spectrumutilization opportunity;\nfurthermore a scenario is also proposed for secondary channel usage....
With shrinking spectral bandwidths and more intense use of the remaining frequency areas, the importance of good electromagnetic\ncompatibility (EMC) performance of professional wireless microphone systems, as used by broadcasters, is increasing. A wireless\nmicrophone system consists of one or more pocket or handheld transmitters and usually the same amount of receivers. Both have to\nbe immune against disturbances, and on the other hand they should not produce interferences.\nThis paper deals with electromagnetic compatibility (EMC) performance tests of three analogue professional wireless microphone\nsystems. The authors describe the complete measurement procedure using two different setups. These setups employ the pocket\ntransmitter or the receiver as device under test (DUT). Different disturbance signals are used utilizing amplitude modulation (AM),\nfrequency modulation (FM) or digital video broadcast-terrestrial (DVB-T). The audio quality of the transmission system is rated with the\ntotal harmonic distortion plus noise (THD+N). Additionally, the authors investigate intermodulations (third harmonic) caused by the\ntransmitter. The results of all performance tests are extensively discussed....
Wireless video multicast has become one of the key technologies in wireless applications. But the\nmain challenge of conventional wireless video multicast, i.e., the cliff effect, remains unsolved. To overcome\nthe cliff effect, a hybrid digital-analog (HDA) video transmission framework based on SoftCast, which transmits\nthe digital bitstream with the quantization residuals, is proposed. With an effective power allocation algorithm and\nappropriate parameter settings, the residual gains can be maximized; meanwhile, the digital bitstream can\nassure transmission of a basic video to the multicast receiver group. In the multiple-input multiple-output\n(MIMO) system, since nonuniform noise interference on different antennas can be regarded as the cliff effect\nproblem, ParCast, which is a variation of SoftCast, is also applied to video transmission to solve it. The HDA\nscheme with corresponding power allocation algorithms is also applied to improve video performance.\nSimulations show that the proposed HDA scheme can overcome the cliff effect completely with the transmission\nof residuals. What is more, it outperforms the compared WSVC scheme by more than 2 dB when transmitting\nunder the same bandwidth, and it can further improve performance by nearly 8 dB in MIMO when compared with\nthe ParCast scheme. �© The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution\nor reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. [DOI: 10.1117/1.JEI\n.25.1.013006]...
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