Shivakumar Ramu.

Video CommunicationBy Dr. Hari Kalva.

Video Streaming over IP Networks.

Introduction

Streaming Video is becoming increasingly prominent on the Internet.

Although some progress has been made in media delivery, today’s solutions (e.g., RealPlayer and Windows Media Player) are proprietary, inflexible, and do not provide the user with a pleasant viewing experience.

The lack of an open framework obstruct innovative research, particularly in the area of video delivery that adapts to changing network conditions.

While today’s streaming applications are closed and proprietary.

Goal of this presentation. Packet loss in Streaming Video. Packet loss recovery for Streaming

video by Selective reliability. Receiver Post processing.

Overview of the presentation.

Goal

Goal -Want a high quality streaming video over IP.

Problems - Variable Bandwidth. - Variable Delay. - Packet Loss. Approach. - Protocol that enables receiver Driven

packet loss recovery using the Selective retransmission and Receiver post processing.

Impact of Packet loss

Packet losses in compressed video are caused by propagation of errors.

Propagation of errors.

An MPEG Picture Structure.

Inter frame dependencies in MPEG Bit stream.

I – Picture. P – Predictive Picture. B – Bi- Directional predictive

Picture.

Selective Reliability.

MPEG-4 structure allow to recover only some important data in bit stream.

By recovering the I-frame data or the P-frame data via Selective reliability, improves the quality of the receiving video.

Recovering B-Frame data is of no use.

Recovering reference frame data using Selective reliability.

Selective reliability increase the quality of the video by up to 3 times.

System Architecture.

Server Packetize the video and labels the packet with ADU sequence number and offset, and sends the RTP packets over UDP.

Client sends the ACK to the receiver, acknowledge the successful receipt of the ADU.

Alternatively, client can send the retransmission request, requesting specific portion of the bit stream.

Receiver Driven Post processing.

Recovering a lost Motion packet – by preceding P Frame.

Recovering a lost Texture packet – by preceding I Frame.

Conclusion

Streaming compressed video over IP, must account for Packet loss.

By recovering most important data in the bit stream will significantly improve the performance gains.

Extension of RTP to enable Selective transmission of important data in conjunction with the receiver post processing will be more efficient way of video streaming over the IP.