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Video surveillance systems video compression and streaming by na b
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Video surveillance systems video compression and streaming by NA B
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| Article Posted: 06/08/2011 |
| Article Views: 104 |
| Articles Written: 2638 - MORE ARTICLES FROM THIS AUTHOR |
| Word Count: 675 |
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Video surveillance systems video compression and streaming |
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Business,Business News,Business Opportunities
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Traditional analog-based systems, many problems are affecting the digital-based systems forward.
IP video surveillance systems (VSIP), the hardware processing of network traffic is an integral part of the camera. This is because the camera Digital Video signal, and to overcome network bandwidth limitations, signal transmission to the video server is compressed before. For different types of processor architectures, such as DSP / GPP, is to achieve maximum system performance desired. Interrupt-intensive tasks, such as video capture, storage and video stream can be assigned to the GPP, the MIPS-intensive video compression by the DSP to complete. Data transmission to the video server, the server files are stored compressed video stream to disk, it can overcome the traditional analog memory device performance degradation.
For the digital video signal compression has developed a wide range of standard, can be summarized as follows:
Road still image compression? Independently coded each video frame as a still image. The most famous standard is JPEG. MJPEG standard encoding each frame with the JPEG algorithm.
Figure 1 shows the block diagram of H.264 encoder. Similar to other ME based video coding standard, which depend on macro-cell (16 × 16 pixels) per frame macro processing unit (macroblockMB). It has a forward path and the reconstruction of pathways. Prior to channel coding frame for the position. Channel coding bits generated from the reconstruction of a reference frame.
The first to access (DCT to Q), each MB can be encoded within the mode or interactive mode. Including the model, by ME module obtained encoding earlier reference MB. In interactive mode, the sampling frame is formed from M.
Reconstruction path (IQ to IDCT) aims to ensure that encoder and decoder for the same reference frame to generate the image. In addition, between the encoder and decoder error will accumulate.
As often contain a lot of video frame timing information, the ME-based method can achieve higher compression ratio. For example, for NTSC standard resolution (30f / s), H.264 encoder can encode video at 2mbps, to 60:1 compression ratio than both image quality. In order to achieve a similar quality, MJPEG compression ratio is about 10:1 ~ 15:1.
MJPEG and ME-based method has several advantages compared to. The main advantage, JPEG requires relatively few computing and power consumption. In addition, the majority of PC software has to decode and display JPEG images. A small amount of images in a single image or record a special event (such as a person entering the door), the MJPEG and more effective. If not guarantee network bandwidth, then the preferred MJPEG. By ME-based method, a frame delay / loss will lead to the GOP's delay / loss, because the next one will not be decoded until the first reference frame is available so far.
In a typical digital surveillance systems, from sensor to capture video, compressed video, and data stream to video server. Do not want to interrupt the DSP architecture of the video encoder to achieve the task, this is because each context switch converter contains a large number of register storage and ultra high-speed buffer memory switch. Therefore, for different types of structure is ideal, so the video capture and data flow task can set off DSP. Below used in video surveillance applications, the DSP / GPP processor instance.
DSP / GPPSoC-based systems in the digital video signal compression, the developer should first ensure proper allocation of modules to achieve good system performance.
EMAC driver, TCP / IP network stack and HTTP server (with the flow to the external work with the compressed video signal), and ATA drive should be realized in the ARM, which helps to off set DSP processing. Compression should be implemented in DSP cores, which is due to its VLIW architecture to handle such computationally intensive task is especially good. I am an expert from China Auto Suppliers, usually analyzes all kind of industries situation, such as pedal toy car , children's rocking horse.
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