Nowadays mobile video streaming services become very popular. However, due to the drastic bandwidth fluctuation in a mobile network, the quality of the mobile video streaming degrades significantly. Above all, mobile ...
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ISBN:
(纸本)9781467398145
Nowadays mobile video streaming services become very popular. However, due to the drastic bandwidth fluctuation in a mobile network, the quality of the mobile video streaming degrades significantly. Above all, mobile users are not happy when video image freezes for a few seconds/minutes. Most of current video streaming services are working as an OTT (over the top) service, which means a mobile network is regarded as a dumb pipe. Therefore it is very difficult to handle the fluctuation. We propose a novel video streaming method in which a QoS control function of a mobile network is utilized to prevent the video image from freezing. In the proposed method, an original video content is encoded into a sequence of video frames with multiple layers. There are two kinds of layers, a base layer and an enhancement layer. The base layer is small in size but includes all the necessary information to play the original content. The enhancement layer is large in size and provides better image resolution when decoded with a corresponding base layer. Then the base layer is prioritized by the QoS control function in the mobile network when it is delivered to a mobile terminal. On the other hand, the enhancement layer is delivered in a best effort manner. In this way, the mobile terminal can receive the base layer even when wireless signal is degraded and the video image dose not freeze at all. The proposed method is evaluated experimentally using a prototype system. The result of the evaluation shows that the proposed method works properly as we designed.
Visible light communication (VLC) is considered a solution to the scarcity of radio frequency communication resources due to its abundant spectrum resources and rapid intensity modulation capability. It has a wide ran...
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ISBN:
(纸本)9781728190549
Visible light communication (VLC) is considered a solution to the scarcity of radio frequency communication resources due to its abundant spectrum resources and rapid intensity modulation capability. It has a wide range of applications in indoor positioning and intelligent transport systems. For example, in Connected and Autonomous Vehicle scenarios, VLC uses traffic lights to warn vehicles at different distances in abnormal situations, thus preventing potential traffic accidents. To facilitate fast, long-range VLC communication in such one-to-many communication scenarios, current systems typically use optical cameras or digital micro-mirror devices as receivers. However, there are several challenges associated with these devices. Optical cameras have a limited sampling rate, resulting in reduced effective throughput. Other receivers, such as digital micro-mirror devices, are relatively costly, which hinders their widespread use. In this paper, we propose a novel, low-cost, and high-speed VLC scheme. We use a low-cost material called Polymer-Dispersed Liquid Crystal as the measurement matrix, reducing the cost by 99% compared to digital micro-mirror devices. We implement hierarchical coding based on compressive sensing to reduce data redundancy and thus improve communication throughput. Empirical experiments conducted using four photodiodes at the receiver show a 120% improvement in overall throughput compared to existing one-to-many VLC systems.
Recently, mobile video streaming services become very popular. MPEG-DASH is one of the streaming schemes used for the service. In this method, a mobile terminal tries to download video chunks from a streaming server b...
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ISBN:
(纸本)9781509016983
Recently, mobile video streaming services become very popular. MPEG-DASH is one of the streaming schemes used for the service. In this method, a mobile terminal tries to download video chunks from a streaming server by estimating the available bandwidth of the underlying network. However, it is very difficult to estimate the available bandwidth because this method is working as an OTT (over the top) service, which means the network is regarded as a dumb pipe. Therefore some of the downloaded video chunks are discarded when the estimation is wrong. Since wireless spectrum is a very precious resource, the wasted chunks (downloaded then discarded) should be avoided. We propose a novel video streaming method in which a QoS (Quality of Service) control function of a mobile network is utilized. In the proposed method, an original video content is encoded into multiple layers. There are two kinds of layers, a base layer and an enhancement layer. The base layer is small in size but includes all the necessary information to keep playing the video content. The enhancement layer is large in size and provides better image quality when decoded with a corresponding base layer. Then the base layer is prioritized by the QoS control function in the mobile network when it is delivered to a mobile terminal. On the other hand, the enhancement layer is delivered in a best effort manner. In this way, even if there were no available bandwidth for both of the layers, the mobile terminal can keep playing the video by using the prioritized base layer. Since the enhancement layer is discarded before the wireless transmission when it is congested, the wireless spectrum is efficiently used.
In this paper, we propose a high frame rate screen video compression scheme aiming at improving the interactive user experience on screen sharing applications. The proposed screen video compression is performed as two...
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ISBN:
(纸本)9781479934331
In this paper, we propose a high frame rate screen video compression scheme aiming at improving the interactive user experience on screen sharing applications. The proposed screen video compression is performed as two-layer coding: a base layer coding using the conventional video codec and an enhancement layer coding using the proposed open-loop coding scheme. For efficient frame level layer selection and compression, the content update of each frame is evaluated through global motion detection. The screen frame with significant content update is fed to the conventional video encoder in base layer. In contrast, the frame with little update is compressed in enhancement layer in which the duplicate content is indicated by global motion vector and skip flag while the updated content is encoded by distinct intra modes in terms of inherent local features. The experimental results demonstrate that for the screen video containing interaction, the proposed coding scheme can achieve 3.09ms/frame encoding rate and 2.33ms/frame decoding rate with efficient rate distortion performance.
In this paper, resource allocation problem for multicast service in OFDM-based wireless cellular networks is investigated and a coding-based opportunistic scheduling scheme is proposed. In the proposed scheme, accordi...
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ISBN:
(纸本)9781467309899
In this paper, resource allocation problem for multicast service in OFDM-based wireless cellular networks is investigated and a coding-based opportunistic scheduling scheme is proposed. In the proposed scheme, according to frequency resource and time resource, layered coding and erasure-correction coding are adopted, respectively. Layered coding divides the data into base layer and enhancement layer, which transmits the data in different rates to maximize the system capacity;erasurecorrection coding compensates for the possible packet loss due to instantaneous channel information. To complete subcarrier allocation and bit loading for the coding-based scheme, a practical algorithm is designed. As only the users;mean channel gains are required, the proposed scheme reduces the overheads required for instantaneous channel information and is suitable for a fast time-varying fading environment. Numerical results show that the coding-based scheme can get significant performance improvement compared with the scheme without coding.
The Scalable Video coding (SVC) amendment ofH.264/AVC provides benefits for a variety of video applications. One particular interesting application area is the backward-compatible format enhancement in video broadcast...
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ISBN:
(纸本)9781617388767
The Scalable Video coding (SVC) amendment ofH.264/AVC provides benefits for a variety of video applications. One particular interesting application area is the backward-compatible format enhancement in video broadcast. The coding efficiency in broadcast applications is usually limited due to a frequent insertion of random access points. In this paper, we show that the coding efficiency for SVC broadcast can be improved by increasing the interval between enhancement layer random access points. With the introduction of adequate constraints for random access points and a minor adjustment of the decoding process at a channel change, this improvement can be achieved without any impact on the channel change delay. In our experiments, the coding efficiency for spatial scalable coding became virtually identical to that of single-layer coding while providing the same channel change delay characteristics.
In mobile cloud gaming, one of the main challenges is to deliver high-quality game images over wireless networks under stringent delay requirement. To reduce the bit-rate of game images, we propose Layered coding, whi...
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ISBN:
(纸本)9781479957521
In mobile cloud gaming, one of the main challenges is to deliver high-quality game images over wireless networks under stringent delay requirement. To reduce the bit-rate of game images, we propose Layered coding, which leverages the graphic rendering capability of modern mobile devices to reduce transmission bit-rate. Specifically, we render a low-quality local game image, or the base layer, on the power-constrained mobile client. Instead of sending the high quality game image, the cloud server sends enhancement layer information, which the client utilizes to improve the quality of the base layer. Central to the proposed layered coding is the design of base layer (BL) rendering. We discuss BL design and propose a computationally-scalable Phong lighting that can be used in BL rendering. We performed experiments to compare our layered coding with state-of-the-art, which uses H.264/AVC inter-frame coding to compress game images. With game sequences of different model complexity and motion, our results suggest that layered coding requires substantially lower data-rate. We made available game video test sequences to stimulate future research.
A new scheme of layered coding of stereoscopic video based on the correlation of motion vector fields (MV fields) is proposed in this paper, in which the bit streams robustness is improved to error channel and the cod...
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ISBN:
(纸本)9781424458653
A new scheme of layered coding of stereoscopic video based on the correlation of motion vector fields (MV fields) is proposed in this paper, in which the bit streams robustness is improved to error channel and the coding efficiency is not reduced evidently. In our proposed scheme, the stereoscopic video is classified into one base layer and two enhancement layers. First, left-view video is encoded as Base Layer to ensure the basic quality of two-dimensional video. Then, the disparity vectors(DVs) of right-view video are encoded as Enhancement Layer 1. To lower bit rates further and reduce the network load, the strong correlation of the motion vectors(MVs) for two views video sequence are tested. Based on the correlation of MVs between views, the MVs of rightview are transmitted as Enhancement Layer 2 only if the correlation between left and right view is less than some threshold. Experimental results are demonstrated to testify the efficiency of our proposed scheme.
A new approach to hybrid digital-analog (HDA) video transmission over orthogonal frequency division multiplexing (OFDM) channels is presented. The goal is to achieve the best video quality by optimal power allocation,...
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ISBN:
(纸本)9781538646595
A new approach to hybrid digital-analog (HDA) video transmission over orthogonal frequency division multiplexing (OFDM) channels is presented. The goal is to achieve the best video quality by optimal power allocation, when the OFDM sub-channels have unequal and time-varying signal-to-noise ratios (SNR). In this method, the quantization error of a video encoder is superimposed on digital quadrature amplitude modulation (QAM) symbols. A solution to the power allocation problem is presented. Experimental comparisons with layered video coding and adaptive modulation shows that the proposed HDA approach is able to achieve a better video quality most of the time, particularly whenever there is a high motion content.
Bakalářská práce se zabývá hierarchickým kódováním – škálováním – pohyblivých obrazů u v současné době velmi využívaných kompresní...
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Bakalářská práce se zabývá hierarchickým kódováním – škálováním – pohyblivých obrazů u v současné době velmi využívaných kompresních algoritmů MPEG-2 a MPEG-4. Škálování je proces, při němž je kódovaný datový tok rozdělen do odstupňovaných vrstev, přizpůsobených především možnostem přenosových médií a schopnostem koncových zařízení. Obsahem základní vrstvy je signál v omezené kvalitě. Obsahem jedné či více rozšiřujících vrstev je pak doplňující obrazová informace, rozšiřující signál na plnohodnotný tvar. Dekodér v závislosti na svých schopnostech a vnějších okolnostech může dekódovat pouze relevantní vrstvy z přijatého bitového toku. Práce se v teoretické části zaměřuje na podrobný popis kódování a dekódování videosignálu dle standardů MPEG při použití tří typů škálování. Konkrétně se jedná o prostorové, kvalitativní SNR a Fine granular škálování. V praktické části práce byla vytvořena výuková aplikace v prostředí Matlab, s vlastním grafickým uživatelským rozhraním, jenž v sobě implementuje funkce provádějící prostorové, kvalitativní SNR a Fine granular škálování. Na základě uživatelsky zadaných vstupních parametrů provádí škálování obrazu a následně zobrazí výstupy jednotlivých vrstev po provedení škálování a po rekonstrukci obrazu. Vstupem programu, na němž je hierarchické kódování prováděno, je obrázek v podobě bitové mapy libovolných rozměrů, ve formátu RGB.
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