The technical development of the network camera is the core force to promote network monitoring. To achieve a satisfactory network monitoring effect, here are the core technologies of cameras such as audio and video compression.
First, the network video camera audio and video compression algorithm
Audio and video compression technology is based on statistical features and human sensory characteristics of digitally sampled video and audio waveform signals, compresses redundant data and sensory insensitive information in the signal, and greatly reduces the amount of data transmitted and stored on the network. At present, the mainstream video compression algorithms are mainly based on hybrid coding framework. Through motion estimation, space/frequency domain transform and quantization, and entropy coding technologies, the redundant information of the video signal in the time domain, air domain, and probability distribution is compressed to obtain low bandwidth and High-quality video images; various audio compression algorithms target multiple applications such as low-bandwidth voice, multi-channel, and high fidelity, and adopt multiple compression strategies to reduce the audio bit rate and increase the fidelity. With the development of networking and digitization, audio and video compression technology has become the cornerstone of the modern security surveillance industry.
In IP cameras, audio and video encoding and decoding are indispensable processes. Currently the most advanced H.264 video compression technology can obtain more than 100 times the compression ratio, making the original data rate of up to 750Mbit/s 1080P30fps high-definition video, with better picture quality in 8Mbit/s or even 4Mbit/s IP environment In the transmission, to overcome the key bottlenecks in the popularization and application of IP camera products - transmission and storage bandwidth consumption, which greatly increased the product's practical value. At the same time, application technologies such as multi-streaming, digital watermarking, and information encryption for audio and video data compression have also greatly improved the applicability and security of products and become an important part of the security monitoring front-end.
At present, in the video surveillance system, the video compression methods mainly include JPEG/MPEG-4/H.264. Each compression method has different characteristics. M-JPEG can obtain the highest single picture quality, but the compression efficiency is low. The maximum bandwidth is occupied; H.264 can obtain the highest compression ratio and the highest processing platform requirements for the camera itself. Users can configure different encoding methods according to different product positioning. For example, the D1 image of the lower bit rate H.264 video compression format is transmitted to the remote site for real-time monitoring of the client, and the real-time image of the megapixel H.264 video compression format is transmitted to the storage server for recording. Thanks to the H.264 compression standard. In the case of the same amount of data, compared to the MPEG4 standard, the compressed capacity of H.264 is only 20% after MPEG4 compression, which means that the same storage capacity of H.264 is five times that of MPEG4, which can be greatly reduced The user's storage costs, and the image transmission quality will not change. In addition, megapixel JPEG images can be transmitted at the time of the alarm, making it easy to confirm after zooming in and find suspicious objects.
Second, the contrast analysis of SDI camera and network camera
The problems of large delay, coding and decoding loss, and high bandwidth of network cameras have not been solved. Manufacturers and users are desperately seeking better HD solutions. Under this demand, a new application has been created - the broadcast-standard SDI has been introduced into security applications to achieve real-time, real-time HD. HD video cameras based on the HD-SDI standard interface are among them.
SDI is based on the concept of 'digital bone, CCTV is shaped', that is to say, digital signals following the SDI specification transmit uncompressed video on the video line/BNC interface, ie 'digital bone'; and the system The installation method is exactly the same as that of CCTV. That is, 'CCTV is shaped'. The advantage of this approach is that it does not require additional learning costs and network monitoring-like after-sales service costs and manpower for the project provider or user.
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