KEYWORDS: Video compression, Motion estimation, Video, Computer programming, Quantization, Video processing, Video coding, Signal to noise ratio, Visualization, Switches
A motion estimation/compensation scheme which is very effective for interlaced sequences with fast motion is presented. This field-based processing technique is MPEG-2 compliant and has lower memory and processing requirements than those of the standard bi-directional frame-based approach. For effective compression of different video sources, a novel temporal processing architecture is described which can switch in real-time between different MPEG-2 compliant field/frame processing modes.
KEYWORDS: Video, Multiplexers, Asynchronous transfer mode, Video processing, Autoregressive models, Video coding, Lithium, Visualization, Information visualization, Modulation
We have studied the video packet loss due to excessive queueing delay in a single statistical multiplexer. The underlying video codec is assumed to separate its outputs into high-priority data and low-priority data so that the loss of low priority will cause a modest picture degradation. In conjunction with such hierarchical coding, the video multiplexer employs a control scheme that selectively discards low-priority data to alleviate the possibility of overload. The quality of the received pictures is measured by the expected underload period and the expected number of high-priority arrivals during an overload period. The former quantity measures the mean period that the received picture stays free of serious disturbance by packet loss due to excessive queueing delay, while the
latter is an indicator of the picture area affected. We have analyzed the performances of such a system under the given control scheme. Our analysis shows that the simple congestion control based on selective packet discarding can significantly prolong the underload period and reduce the number of high-priority losses in the overload period. To further reduce the number of high-priority arrivals in overload periods, we propose a control scheme that blocks all arrivals once they exceed the maximum delay. Moreover, the underload period can be dramatically prolonged by reducing the packetization buffer at the network input end. These results show that transporting video by the ATM technique is very promising.
KEYWORDS: Video, Image processing, Multiplexers, Visual communications, Signal attenuation, Video processing, Asynchronous transfer mode, Quality measurement, Visual process modeling, Control systems
In this paper we will study the video packet loss due to excessive queueing delay in a single statistical multiplexer. Because of the real time nature of video service, packets exceeding a time constraint will be declared lost at the destination. Any packet arriving during the period when the queue length exceeds the threshold determined by the time constrain will be dropped at the destination. Thus, packet losses occur in clusters. We measure the quality of the received pictures by the expected underload period and the expected number of high priority arrivals during an overload period. The former quantity measures the frequency of packet dropping due to excessive delay, while the later is an indicator of the picture area affected.
We analyze and compare two system schemes, where the first scheme drops late packets only at the destination and the second one blocks arrivals in front of the multiplexer once the packets exceed the permissible delay. Comparison of the two system schemes based on the two measurements mentioned above indicates that the second scheme is superior to the first one. In order to further improve the video service quality, a simple congestion control based on the dynamics of queue length is proposed. Our analysis shows that the proposed control scheme significantly extends the expected underload period.
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