Multiresolution-multicast video distribution over the Internet

Multimedia distribution over the Internet is becoming increasingly popular. Since the Internet was designed for computer data communication, satisfying the different characteristics and requirements of multimedia streams poses significant challenges. For effective and efficient Internet video streaming, many issues (e.g., multiresolution representation, multicast transmission, error control, synchronization, etc.) must be addressed. In the paper, a novel framework for Internet video streaming is proposed. For video compression, our previously developed three-dimensional significance-linked connected component analysis (3D-SLCCA) codec is applied. 3D-SLCCA provides high coding efficiency, multiresolution video representation, transmission error resilience, and low computational complexity. For audio coding, the GSM standard is used. For error control, retransmission and error concealment are jointly applied. Multiresolution-multicast transmission is implemented by assigning different multicast group addresses to different video layers. Thus each receiver subscribes to the maximum number of layers that both its hardware resource and network capability can handle. By using hierarchically structured multicast tree, each node is responsible for caching packets, collecting NACK packets, and sending repair packets. This not only significantly reduces the latency, but also efficiently solves the "ACK implosion" problem. As opposed to data transmission, reliable multicast is not required by the network infrastructure. Based on timing constraint and the importance of lost packets, each receiver decides whether to request retransmission or apply error concealment. Finally, synchronization is accomplished by using the timestamp mechanism of RTP. When the network does not support multicasting, proxy servers implemented on workstations can be used to perform similar functionalities.