3G, Internet, telecom bodies endorse video protocol
By Martyn Williams
THE MAIN GROUP coordinating the technical standards for current and 3G (third generation) wireless services, the Third Generation Partnership Project (3GPP), is backing a Japanese proposal for transmission of digital video over networks in a move to bring compatibility to wireless and wireline networks.
With the backing of 3GPP, the new transfer format for MPEG-4 digital video now has the support of three major technical bodies. The Internet Engineering Task Force (IETF) and International Telecommunications Union (ITU) announced support for the standard in October and November respectively last year, said the five companies that jointly proposed the system: Toshiba, NEC, Oki Electric Industry, Matsushita Electric. and Nippon Telegraph and Telephone.
"This brings the standardization of MPEG-4 and RTP (Real-time Transfer Protocol) over the Internet and wireless networks," said a spokeswoman for Toshiba. "People have been sending video over networks before but it has all been different formats. By using a standardized format, everyone can see everything with no problem."
The standardization is especially important if video telephone calls are to be successfully placed between telephones, cellular handsets and personal computers because the calls will transverse different networks.
The new transfer system is based on RTP, a system standardized by the IETF for IP (Internet protocol) networks in 1996 and intended for use on large scale networks. It is designed to run on UDP (Uniform Datagram Protocol), unlike today's TCP/IP (Transfer Control Protocol/IP)-based systems.
Current systems are designed with an emphasis on reliable data transmission. This means mechanisms are put in place to ensure as much of the original data stream as possible is recovered at the destination. One such mechanism allows the destination computer to request retransmission of lost data but this necessitates buffers -- something that delays time sensitive streams like real-time video.
In contrast, RTP has an emphasis on speed and includes no mechanisms for recovering lost data. On high performance networks this should mean video and audio are delivered in a more timely fashion. Another advantage lies in a time-stamp that is added to the RTP header inside each packet and which enables synchronization of audio and video.
Toshiba began working on the system at the beginning of 1999, just after the MPEG-4 standard was approved in late 1998, and has been leading the group. In October, 1999 it approached the other four companies and asked for their backing and support of development of the system, and went on to jointly propose it to the standardization bodies last year.
Technical details of RTP can be found online at www.ietf.org/rfc/rfc1889.txt and www.cs.columbia.edu/~hgs/rtp/faq.html
