Hassan Mehrpour

Scene change detection algorithm for MPEG video sequence

A new scene change detection algorithm is developed for MPEG encoded video sequences. The proposed method is very simple that it only requires the bit-rate information at macroblock level as well as the number of various motion-predicted blocks for detection. Those information can be extracted easily from the encoded bit-stream without decompression. Simulation results on different sequences show that the proposed algorithm is effective for detecting abrupt scene changes in MPEG video.

Adaptive block matching motion estimation algorithm using bit-plane matching

Motion estimation/compensation techniques are extensively used in video compression because of their abilities to exploit the high temporal correlation between successive frames of an image sequence. We first propose a new matching criterion called bit-plane matching (BPM) for distance measurement in the block matching algorithm. This criterion not only considers the magnitude but also the directive information of the pixel elements in the block. A simple adaptive block matching algorithm is also developed to adjust the search origin and search range at a block-by-block basis. Simulation results show that the proposed algorithm achieves similar MSE performance for motion-predicted images but requires about 8 times less the number of computations than the full-search method.

Error concealment for MPEG video transmissions

Packet loss is a critical problem for video transmission on packet-switched networks. An error compensation method called the modified boundary matching algorithm is developed for recovering lost video due to packet loss at the video decoder. Simulation results demonstrate that the proposed method preserves good image quality even when the cell loss rate is very high.

Survey: Flow control in ATM networks: a survey

In this paper, we present results of a study of flow control in ATM networks. Two classes of flow control are described: preventive and reactive. A preventive control, which uses a static resources allocation, seems inadequate to handle rough traffic in high speed networks. On the other hand, the reactive control schemes, which employ a closed-loop feedback mechanism, seem more attractive than the preventive control schemes, especially in ATM networks. Four ATM service categories are provided to serve a variety of users. To enable each service class to function effectively two closed-loop flow control mechanisms: rate-based and credit-based, have been introduced for ATM networks. Rate-based flow control schemes use the rate of traffic flowing from the source to control the transmission rate. In this paper, a number of variants of rate-based schemes are described and analysed. Credit-based schemes use window flow control where a traffic source is allowed to transmit data only when there is available buffer space in the downstream node. In this paper, a number of credit-based schemes are also described and analysed.

Cell loss concealment method for MPEG video in ATM networks

Cell loss is inevitable in ATM networks due to network congestion and appears to be a critical factor affecting the quality of the video signal. For transmitting MPEG video over ATM networks, cell loss causes error propagation in both the spatial and temporal domain, which in turn leads to severe degradation in the image quality. We first introduce a structural method for packing MPEG video bit-stream into ATM cells. With this method, the impact of cell loss can be limited to the lost cells only. A cell loss compensation method called modified boundary matching algorithm is then proposed for transmitting the MPEG video bit-stream in ATM networks. Simulation results demonstrate that the proposed method yields satisfactory results even when the cell loss rate is very high.

Loss recovery techniques for transmission of MPEG video over ATM networks

Cell loss is a critical problem for transmission of video over ATM networks. We first introduce a structural method for packing MPEG video bit-stream into ATM cells. With this method, the impact of cell loss can be limited to the lost cells only. A compensation method called the modified boundary matching algorithm is then proposed for recovery of the lost video information. Simulation results demonstrate that the proposed method yields satisfactory results even when the cell loss rate is very high.

Delay performance of a leaky bucket regulated multiplexer based on burstiness characterization

In high-speed networks, a congestion control strategy has to manage bandwidth allocation according to the characteristics of the input sources. The definition of traffic characterization is significant in all aspects concerning network performance. Using the burstiness characterization based on a virtual queue principle, we analyze the delay performance of a leaky bucket regulated multiplexer, and investigate the effectiveness of a leaky bucket in protecting a delay bound of a multiplexer system. Numerical results show that a leaky bucket can provide a well-behaved traffic stream with guaranteed delay bound in the presence of a misbehaving traffic stream.

Motion adaptive classified vector quantization for ATM video coding

In this paper, a two-layer motion adaptive classified vector quantizer (MACVQ) is proposed for ATM video coding. The proposed method classifies image blocks into three different motion classes: slow-motion, medium-motion and fast-motion. Specified vector quantizers are then designed to encode different motion blocks. A simple edge-based classified vector quantizer is developed to encode the motion-compensated prediction (MCP) error. Compared with the MPEG-type DCT interframe coder, the proposed MACVQ coder has better MSE performance and less accumulation error between consecutive frames. >

Simulation analysis on statistical multiplexing of MPEG video sources

In this paper, we first investigate the impacts of different interleaving and synchronization schemes on the performance of an ATM multiplexer using real MPEG data. A source scheduling method is then developed to improve the performance of the multiplexer. Experiment results show that the level of burstiness for the aggregated MPEG traffic is reduced and the network performance in terms of cell loss probability and statistical multiplexing gain is greatly enhanced.

Packet reservation multiple access for multimedia traffic

Packet reservation multiple access (PRMA) was designed to support only voice and data traffic. To investigate the performance of PRMA for video transmission, a modified version of PRMA needs to be considered. A modification to the PRMA protocol proposed to support video traffic was investigated using computer simulation. A real video trace file from H.261 codec was used as video traffic for simplification and accuracy in the simulation study. The results show that the modified scheme for supporting H.261 video traffic could provide acceptable quality-of-service at a given number of video terminals in the system. Furthermore, the modified PRMA could support simultaneously 28 voice terminals operating at 32 kbps, 28 data terminals generating data packets at a rate of 1200 bps, and one H.261 video terminal at the mean bit rate of 64 kbps, at the channel rate of 720 kbps in the system.