Yo-Won Jeong

Interactive media server with media synchronized RAID storage system

We propose an efficient placement algorithm and per-disk prefetching method to effectively support interactive operations in the media server. Our placement policy is incorporated with an encoder having a special bitcount control scheme that repeatedly tunes quantization parameters to adjust the bitcounts of video frames. This encoder can generate coded frames sub-stream video blocks whose sizes are synchronized with the RAID stripe size, so that when various fast-forward levels are accessed we can reduce the seek and rotational latency and enhance the disk throughput of each disk in the RAID system. In the experimental results, the proposed placement policy and bitrate control scheme can significantly improve the average service time, which can enlarge the capacity of the interactive media server.

Data placement and prefetching with accurate bit rate control for interactive media server

An interactive Media Server should support unrestricted control to viewers with their service level agreements. It is important to manage video data effectively to facilitate efficient retrieval. In this paper, we propose an efficient placement algorithm as part of an effective retrieval scheme to increase the number of clients who can be provided with interactive service. The proposed management schemes are incorporated with a bit count control method that is based on repeated tuning of quantization parameters to adjust the actual bit count to the target bit count. The encoder using this method can generate coded frames whose sizes are synchronized with the RAID stripe size, so that when various fast-forward levels are accessed we can reduce the seek and rotational latency and enhance the disk throughput of each disk in the RAID system. Experimental results demonstrate that the proposed schemes can significantly improve the average service time and guarantee more users service of quality, and the interactive media server can thereby efficiently service a large number of clients.

A New Joint Source-Channel Modeling Approach for Adaptive FEC Code Rate Decision

We propose a joint source-channel modeling approach for adaptively determining the quality-optimal FEC code rate. Our objective is to obtain the optimal video quality in the receiver, while taking time-varying packet loss into consideration. First, we define the loss threshold set as the set of packet loss probabilities in which the code rate have to be adjusted to maintain the maximum video quality. Proposed model can estimate the loss threshold set efficiently. Then, whenever there is a change of the packet loss status in the channel, video sender can always find the optimal code rate on-the-fly by using the estimated loss threshold set. Simulation results show that the proposed method can determine the near-optimal code rate in joint source-channel coding

Piggyback Packetization of Duplicate Packets for Packet-Loss Resilient Video Transmission

The transmission of duplicate packets provides a loss-resilience without undue time-delay in the video transmission over packet loss networks. However, this method generally deteriorates the problem of traffic congestion because of the increased bit-rate for duplicate packet transmission. In this paper, we propose a set of techniques for an efficient packetization and transmission of duplicate video packets. The proposed method transmits the duplicate packet containing high priority data that is quite small in volume but very important for the reconstruction of the video. This method significantly reduces the required bit-rate for duplicate transmission. An efficient packetization method is also proposed to reduce additional packet overhead which is required for transmitting the duplicate data. It is shown by simulations that the proposed method remarkably improves the packet loss-resilience for video transmission only with small increase of redundant duplicated data for each slice.

A New Packet Loss-Resilient Duplicated Video Transmission

The transmission of duplicated packets provides a loss-resilience without undue time-delay in the video transmission. However, this method increases the bit-rate requirement in the network and hence exacerbates the problem of traffic congestion. In this paper, we propose a duplication of high priority data only for each video macro-block that is small but important in the reconstruction of the video. This reduces the bit-rate requirement in the transmission. Also, an effective packetization method is proposed to reduce the additional packet headers which are required to transmit the duplicated data. The duplicated high priority data of the previous video slice is transmitted as a piggyback to the data packet of the current video slice. Simulations indicate that the proposed method remarkably improves the packet loss-resilience for some video with a small increase of redundant duplicated data for each slice

A new raid-disk placement method for interactive media server with an accurate bit count control

In this paper, we propose a RAID-disk placement algorithm of coded video data and an efficient disk prefetching method to increase the number of clients who can be serviced interactive operations in the media server. Our placement policy is incorporated with a special bit count control method that is based on repeated tuning of quantization parameters to adjust the actual bit count to the target bit count. The encoder using this method can generate coded frames whose sizes are synchronized with the RAID stripesize, so that when various fast-forward levels are accessed we can reduce the seek and rotational latency and enhance the disk throughput.