1 an extensible videoconference tool for a collaborative computing network junjun he
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An Extensible Videoconference Tool for a Collaborative Computing
Network
Junjun He
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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
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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
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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
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H.263 Encoding
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H.263 Decoding
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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
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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)
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Videophone Structure
Videophone
Functions GUIH263 Messages DATAQ
TMN 2.0 TMNDec 2.0
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Components of Videophone
Video Capturer
File Reader
Compressor
Video Recorder
VideoTransmitter
Sender
Packet
Receiver
File
Reader
Decompressor
VideoRecorder
Video
Restorer
Receiver
Common
FileReader
VideoRecorder
Initialization
InitializationFunctions
Listener
Utility
CardSender
FileSender
VideoReceiver
Inviter
Stopper
VideoPlayer
MessageRecorder
VideoMaker
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Initialization Module
Initialization Functions Initialize Window Initialize Video Card Initialize CCTL Session Initialize Data Queues
ListenerReceive invitation messages and join a CCTL session
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Sender Module
Video CapturerGet images from a video card
Inter-frame CompressorSpatial compression
Intra-frame Compressor Temporal compression
Video TransmitterTransmit video among a session
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Receiver Module
Packet ReceiverReceive video from other session members
DecompressorDecompress the received video
Video RestorerDisplay decompressed video in a window
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Common Module
File ReaderRead compressed video file into a data queue
Video RecorderWrite compressed video from a data queue to a file
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Utility Module- Card Sender Launcher
Video Card
Video capturer
CompressorVideo Transmitter
Data queue
Data queue
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Utility Module- File Sender Launcher
Video Data File reader
Data queue
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Utility Module- Video Receiver Launcher
Data queue Data queue
Packet Receiver Decompressor Video Restorer Window
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Utility Module- Message Recorder Launcher
Data queue
Video DataVideo Recorder
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Utility Module- Video Receiver Launcher
Data queue Data queue
Packet Receiver Decompressor Video Restorer Window
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Utility Module- Video Maker Launcher
Video Recorder
Data queue
Video Card
Video Capturer
Compressor Target File
Data queue
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Utility Module- Video Player Launcher
Decompressor Video Restorer WindowSource File
Data queue Data queue
File Reader
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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
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One Typical Session Member
Listener Packet Receiver
Member 3Member 2Member 1
Video Receiver 1 Video Receiver 2 Video Receiver 3
Card Sender
In one CCTL channel
TCP/IP
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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
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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
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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
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User Interface- File Operation
Select a file for a video player launcher
Save the video into a file for a video recorder launcher
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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
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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
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User Interface- Decompression Parameters
Output Format specifies what kind of output data the decompressor generates