Video telephony, where users can communicate both through audio and video, has been available for many years. However, since the equipment has been expensive and the networks installed in most users’ homes have not been capable of handling the bandwidth needed for video telephony, it has not got any widespread use. As more people get broadband connected these days it is believed that video telephony will become more popular in the future.
This thesis evaluates and shows an implementation of a video telephony solution for network connected set-top boxes based on the SIP protocol for managing sessions. Unlike other video telephony implementations the set-top box does not handle both audio and video, but only video…
Contents
1 Introduction
1.1 Background
1.2 Purpose
1.3 Limitations
1.4 Methods
1.5 Sources
1.6 Structure
1.7 Glossary
2 IP based set-top boxes
2.1 Hardware
2.2 Software environment
3 Video telephony
4 SIP
4.1 SIP operations
4.1.1 Setting up a session
4.1.2 Modifying a session
4.1.3 Terminating a session
4.1.4 Location registration
4.1.5 Capability discovery
4.2 SIP building blocks
4.2.1 User agent
4.2.2 Proxy
4.2.3 Registrar
4.2.4 Back-to-back user agent
4.3 Locating SIP users
4.4 SIP message structure
4.5 SDP
4.5.1 Media negotiation
5 Media transport
5.1 RTP
5.2 RTCP
6 Image processing
6.1 Colour spaces
6.1.1 RGB
6.1.2 YUV
6.2 Video Compression
6.3 Intra encoding
6.3.1 Discrete Cosine Transform (DCT)
6.3.2 Quantization
6.3.3 Run-length encoding
6.3.4 Huffman coding
6.4 Inter encoding
6.4.1 Conditional replenishment
6.4.2 Motion compensation
7 Project requirements
8 System design
8.1 SIP communication
8.2 SIP implementations
8.3 Video input
8.4 Video compression
8.4.1 Codec implementations
8.4.2 Codec benchmarks
8.4.3 Benchmark results
8.4.4 Benchmark conclusions
9 Implementation
9.1 Video user agent
9.1.1 SIP
9.1.2 Video handling
9.1.3 Image capturing
9.1.4 Colour space conversion
9.1.5 Video compression
9.1.6 RTP packaging
9.1.7 Video rendering
9.2 B2BUA
9.2.1 Audio UA → Audio UA
9.2.2 Audio UA + Video UA → Audio UA + Video UA
9.2.3 Audio UA + Video UA → Audio&Video UA
9.2.4 Standard SIP videophone → Standard SIP videophone
10 Conclusions
10.1 Future enhancements
11 Bibliography
Appendix 1: Video benchmarks
Author: Högberg, Robert
Source: Linköping University
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