the IP Camera server,network server
Network server offer IP Camera's web function feature,which uses RTP / RTCP, UDP, HTTP, TCP / IP and related network protocols, allowing users from their PC, using a standard browser, accordint to the IP address of the network camera to access, view real-time image, and controlthe camera lens and head.
external alarm, control interface
IP cameras provide a practical engineering application of the external interface, such as the head of the 485 control interface, for alarm signal input and output of the I / O port. If infrared probe targets, send alarm signal to the network camera, network camera automatically adjusts the lens direction and real-time video; the other hand, when the network camera detects a moving target appears, can be sent out alarm signals.
The basic principle of the IP camera is: image signal input through the camera and sound signals through the microphone input, sound sensor and the image sensor into electrical signals, A / D converter to convert analog signals to digital signals, through the encoder according to a certain coding standard encoding, and then under the control of the controller, by a certain network protocol,send to LAN and Internet, the controller can also receive alarm signal and send out alarm signals, and send control signals required .
image coding standard
At present, the ip camera image compression coding standard mainly have MPEG4, H.263, H.264, M-JPEG and so on.
MPEG4
The so-called MPEG standard is that the ISO's Moving Picture Experts Group developed a series of audio and video signals, and multimedia signal compression and decompression technologies standards. So far, implementation has been finalized and approved were: 1991 approved MPEG1, MP3; 1994 ratification of the MPEG2; 1999 approved in MPEG4 and MP4. Standards are being developed: MPEG7 and MEPG21.
H.263
H.263 is the end use which ITU-T proposed as H.324 video codec recommendation, as continuously improved and upgraded many times, it has matured, and now replace most of the place of the H.261,and due to the low-bandwidth transmission of high-quality video streaming ,H.63 become more popular.
H.263 is based on motion compensation of DPCM hybrid coding,motion search based on motion compensation, DCT transform and then use "s" shaped scan code to the output stream. Based on H.261,H.263 motion vector search increase to half-pixel search,at the same time ,increased the unrestricted motion vectors, syntax-based arithmetic coding, advanced forecasting techniques and PB frame coding advanced Options, so can lead to further reduce the code rate and improve the encoding quality.
H.264
H.264 is the ITU-T of the VCEG and ISO / IEC for MPEG video group joint development of a new digital video coding standard, it is an ITU-T's H.264, is ISO / IEC of the tenth part of the MPEG4 . In the same reconstructed image quality under, H.264 to H.263 save about 50% higher than the rate, than is currently achieved under the MPEG4 video format in about 33% performance increase.
M-JPEG
M-JPEG static image compression technology that sports technology, which the movement of the video sequence as a series of static images to deal with this compression method to compress each frame individually complete, in the editing process can be randomly stored in each frame can be to frame accurate editing. However, only the frame M-JPEG compression Mainland spatial redundancy, redundancy does not compress the time frame, so compression efficiency is not high.
