1. 1 An Extensible Videoconference Tool for a Collaborative Computing Network Junjun He

2. 2 Introduction The videoconference tool is a real- time desktop videoconferencing tool that can be used in a collaborative environment It uses a software codec to reduce the system requirement for the application It has a very user friendly interface

3. 3 Video Compression Video compression is a good way to reduce both storage and bandwidth requirement Videoconference tool can adopt multiple compression methods The current implementation of videoconference tool uses H.263 as its default compression method

4. 4 H.263 H.263 is the recommendation of the ITU for video coding for low bit rate communication H.263 supports 5 different resolutions: CIF, QCIF, sub_CIF, 4CIF, 16CIF

5. 5 H.263 Encoding

6. 6 H.263 Decoding

7. 7 Video Transmission The videoconference tool requires that the video be received in real- time Real-time video can tolerate data loss, but not data delay CCTL is the transfer protocol used by the videoconference tool

8. 8 CCTL Collaborative Computing Transport Layer is the communication protocol used by CCF CCTL is a multicast protocol which can be configured to satisfy different requirement (QoS)

9. 9 Videophone Structure

10. 10 Components of Videophone Video Capturer File Reader Compressor Video Recorder Video Transmitt er Sender Packet Receiver File Reader Decompressor Video Recorder Video Restorer Receiver Common File Reader Video Recorder Initialization Functions Listener Utility Card Sender File Sender Video Receiver Inviter Stopper Video Player Message Recorder Video Maker

11. 11 Initialization Module Initialization Functions  Initialize Window  Initialize Video Card  Initialize CCTL Session  Initialize Data Queues Listener Receive invitation messages and join a CCTL session

12. 12 Sender Module Video Capturer Get images from a video card Inter-frame Compressor Spatial compression Intra-frame Compressor Temporal compression Video Transmitter Transmit video among a session

13. 13 Receiver Module Packet Receiver Receive video from other session members Decompressor Decompress the received video Video Restorer Display decompressed video in a window

14. 14 Common Module File Reader Read compressed video file into a data queue Video Recorder Write compressed video from a data queue to a file

15. 15 Utility Module - Card Sender Launcher Video Card Video capturer Compressor Video Transmitter Data queue

16. 16 Utility Module - File Sender Launcher Video Data File reader Data queue

17. 17 Utility Module - Video Receiver Launcher Data queue Packet ReceiverDecompressorVideo RestorerWindow

18. 18 Utility Module - Message Recorder Launcher Data queue Video Data Video Recorder

19. 19 Utility Module - Video Receiver Launcher Data queue Packet ReceiverDecompressorVideo RestorerWindow

20. 20 Utility Module - Video Maker Launcher Video Recorder Data queue Video Card Video Capturer Compressor Target File Data queue

21. 21 Utility Module - Video Player Launcher DecompressorVideo RestorerWindow Source File Data queue File Reader

22. 22 Utility Module - Inviter and Stopper An inviter sends an invitation message to all session members and creates a sender utility to send out its own video in the session A stopper stops the reception of the video from a session member

23. 23 One Typical Session Member ListenerPacket Receiver Member 3Member 2Member 1 Video Receiver 1Video Receiver 2Video Receiver 3 Card Sender In one CCTL channel TCP/IP

24. 24 User Interface - System Icon The left videophone button generates 5 menu options:  Invitation  File  Stop  Compression Parameters  Decompression Parameters The right Message button turns on the message recorder feature

25. 25 User Interface - Invitation Guest Names displays all the selected participant’s name Phone Book displays the names listed in the phone.book file User can click name in phone.book to add it into guest names or type in the input field directly to add name to both guest names and phone book Before invite, the user can choose to send out which kind of video

26. 26 User Interface - Invitation Response Receiver can decide to join the session or not Receiver can choose to send what kind of video among the session or not to send video at all

27. 27 User Interface - File Operation Select a file for a video player launcher Save the video into a file for a video recorder launcher

28. 28 User Interface - Stop Operation The Current Participants displays all existing session member’s name in local videophone User can select any member’s name and delete it from local videophone

29. 29 User Interface - Compression Parameters Code Format specifies the size of the compression Compression Method decides how to compress:  Discrete:intra-frame compression  Continuous:inter-frame compression

30. 30 User Interface - Decompression Parameters Output Format specifies what kind of output data the decompressor generates