Research on Video Conference Far Camera Control
Department of Communication Technology, Harbin University of Technology (150001) Yu Bo Liu Jinhui Zhang Zhongzhao
Summary: Analyze how to achieve control over the remote camera in the video conference, which plays a very important role in remote teaching and real-time monitoring. Keywords: Video Conference Winsocket Rules Analyzer With the continuous development of my country's reform and opening up, the conference, meeting, consultations, meetings, meetings, in the upper part of the society, especially in the economic sector, information, time, efficiency and other modernization The concept began to be deep into the hearts, and in the case of the administrative meeting of various industries, the impetition and convenience of the conference television service communication as one of the modern communication methods of advanced countries showed outstanding superiority. The preparation and commissioning of this software is based on the MeetingPoint E25 video conferencing system produced by VCON, and E25 does not have camera control functions, and C150 has camera control functions. That is to say, the mutual control of the camera can be directly performed between the two C150, and the rotation of the remote camera is not feasible using the E25 system. Therefore, writing a software compatible under different systems is very necessary and has practical meaning. 1 Design ideology The overall structure of this software adopts client-server mode. The specific work process is as follows: Through the procedure analyzer, we can measure the specific control signals for the camera. First, the client issues a signal (e.g., LEFT), transmitted to the server via the network, the server writes different control signals to the COM in accordance with different signals, and the camera connected to the COM will make various actions. During the programming process, the connection between the RS-232C and the camera interface is first given, and then the method for determining the control signal with a procedure analyzer is given, and the control signal of the SONY camera is measured. Since the remote camera control is to be implemented, the transmission of the signal is based on the network. Next is the principle of network communication Windows CSocket, which is the key to the rear implementation signal, and the key to this software. 2 Connection to the connection and control signals of the control signal 2.1 Connection to the control line Since the control line is to be controlled, there is a control line between the host COM port and the camera interface, RS-232C and the Sony camera correspondence The connection is shown in Table 1.
2.2 Determination of the control signal Application procedure analyzer can analyze various protocols, and we measure the various control signals whose camera rotation is measured. Some of the control signals are as follows, given in hexadecimal form. 0x883001FF0x88010001FF 0x81090447FF · · initialization signal a right turn DETAILED 0x810106010B090103FF 0x810106010B090303FF · upward turn signal 0x810106010B090301FF0x810106010B090303FF · focus signal 0x8101040724FF 0x8101040700FF0x81090447FF 3 program signal to achieve the program uses a client / server mode, the main function is controlled from a computer connected to another LAN The camera on a computer can be collected at any time in any location in the conference room. Since the control of the camera can be implemented by writing data to serial port, how is the core problem of the program quickly and effectively realizes the network Data exchange. In order to achieve real-time effect, this article uses Windows Socket to realize real-time communication of the network.
3.1 Socket Programming Principles We know that the core part of TCP / IP is the Transport Layer Protocol (TCP, UDP), Network Protocol (IP), and physical interface layers, which are usually implemented in the operating system kernel. The kernel of the operating system cannot be able to feel the general user. General users feel that only applications (including system applications), that is, various applications constitute user views of the operating system. The application is derived by the programming interface (ie, the programmer interface). The application in the TCP / IP network environment is implemented through the network system programming interface socket socket (WINSOCK under Windows operating system). The mode of action between internet applications is the client / server mode. The relationship between the TCP / IP protocol core and the application is shown in Figure 1.
Communication in internet applications is the mutual communication problem between different host processes. To this end, you need to use a three-tuple in the Internet network to uniquely log into a process (protocol, local address, local port number), such a three-tuple called one semi-correlation. And a complete network network process communication instance consists of two processes, so a complete network network process communication (including two end processes) requires a five-way group to log registration (protocol, local address, local port number, far The ground address, the far port number), such a five-tuple called a correlation. The port is the access point of TCP and UDP and applications, which is part of TCP / UDP protocol software. The TCP / IP protocol specifies the use of some standard reserved port numbers (for server processes); user processes can apply for use with non-reserved ports, the flag (port number) of this port is unique. Therefore, the port number is the descriptor of the network process itself. In the TCP / IP network network, the main mode of the two processes between communication is the client / server mode, that is, the client issues a service request to the server, and the server receives the corresponding service. The establishment of the client / server mode is based on the following two points: First, the cause of the network is the uniqueness of the software, calculation capabilities, and information, which requires sharing, resulting in a host providing services with many resources, less resources. Service is a non-equal role. Second, there is neither a parent-child relationship between the processes of each other, and there is no shared buffer, so there is a mechanism to establish a connection between the process that wants to communicate, and provides synchronization for both data, which is based on customer / server Mode TCP / IP. Regardless of the internal mechanism of the Socket, it provides the final interface to the application is a set of system calls: including the creation of the SLNECT and Accept, listening to Listen, and SEND and RECV for data transfer, and close the socket CLOSESOCKET, etc. Figure 2 is a sequence diagram for Socket-facing client / server-based system-based system call.
Two classes are available in VC 5.0 to support network programming with Winsock API. Class CasyNsocket encapsulates the Winsock API function, its network function is very powerful; CSocket is simplified to train data in a CARCHIVE class. Our class is derived from the CSocket class. 3.2 Functional Functions Introduction In this software, client programs and server programs are written in Visual C 5.0. In the MFC class library, there is a special CSocket class that manages Winsock programming. In the CSocket class, it covers all Win32API functions, so when you program with Winsock, just declare an instance with CSocket, then call the corresponding function. Various operations (CSocket class member functions see Visual C Books on line. When using the CSocket class, you must synchronize the CSocketFile class instance.
The main function used in this program describes the following: · CSocket :: Create function prototype: BOOL CREATE (UnitNsocketPort = 0, int NSockettype = Sock-Stream, LPCTSR ipszsocketaddress = null); Features: After the establishment of a socket object, call CREATE function to create a Windows Socket, then call the BIND function to the Socket to assign a specific address. Parameters: NSocketPort: Socket Selected port. NSocketType: Socket Type (Sock-Stream, Sock-DGRAM).
IpszsocketAddress: The network address of the server. · Casynsocket :: Connect function prototype: BOOL Connect (LPCTSR Ipszhostaddress, Unit NhostPost) Bool Connect (Int NSOCKADDRLEN) Function: Call the Connect function to establish a connection with the server. Parameters: Ipszhostaddress: The network address of the server. NHOSTPOST: The port used by the server. IPSockAddr: Presses the address of SockAddr that contains the address of the connected socket.
NSOCKADDRLEN: The length of the address containing IPSockAddr. · GetcommState function prototype: BOOL getcommstate (Handle Hfile, LPDCB LPDCB) Function: Take the current control setting from the specified communication device. Parameters: HFILE: Handle of Communication Equipment. LPDCB: Pointer for DCB structure. · SetCommState function prototype: BOOL SetCommState (Handle Hfile, LPDCB LPDCB) Function: Set control information for the specified communication device. Parameters: The definition of the parameter (HFile.lpdcb) in the same last function.
· WriteFile function prototype BoolWriteFile (Handle Hfile, LPVOID IPBUFERIL, DWORD NNUMBYTES Towrite, LPDWORD IP-Numberofbytes Written, LPOVERLAPPED IPOVERLAPPED) Function: Write data to serial ports, this operation is applicable to synchronous or asynchronous communication. Parameters: HFILE: Serial Element Handle, this serial port is created with Generic-Write mode. IPBuffer: Points to the pointer to contain the data buffer. NNUMBEROFBYTESTOWRITE: The number of bytes written to the serial port. IPNumberofByteswritten: Pointer to the byte of the actual write to serial port data.
IPoverlapped: Pointer to the Overlapped structure. 4 Procedures flowcharts There are two programs in this software, and the flowcharts are shown in FIGS. 3 and 4, respectively. 5 Software Implementation This software can achieve the following four aspects: • The client can control the rotation of the server's camera on the camera; • The client can control the camera's camera focusing and stretching; • Client can be with the server Talk, exchange opinions; · The client and server side can save each other's message. Reference 1 Huang Donglin. Listen to multimedia business. Beijing: Electronic Industry Press, 19972 Michael J. Young. Mastering Microsoft Visual C 4. Beijing: Electronic Industry Press, 1997
(Required Date: 1999-07-13)
