What are the schemes of H.264 coding chip currently used in the security field, such as VDR hard disk camera and HD network camera?

After the concept and promotion, the digital high-definition network camera has been gradually recognized by customers. The digitalization, intelligence, high-definition and networking of security products are an irreversible trend, and high-definition products on the market have mushroomed in front of users. 20 1 1 is the year of high-definition products in the field of monitoring, and words such as "HD" and "IP" have become well-deserved hot words. More and more manufacturers have joined this field, making the cake of HD IP bigger and bigger. At present, there are many high-definition ip solutions on the market, including HiSilicon, TI, NXP, Trident, Techwell, Zhiyuan and many other chip manufacturers have put forward their own high-definition IP solutions. How to choose a suitable HD IP solution has become a very concerned issue.

High definition IP solution

Although there are many schemes for high-definition network cameras on the market, from the perspective of architecture, there are nothing more than the following two basic architectures:

(a) Using CCD/CMOS sensor.

As an image acquisition device, (sensor) supports ISP's SOC chip. This scheme has obvious cost advantages, and the imaging effect of this scheme mainly depends on ISP (such as 3A, Wide Dynamic, etc.). ) integrated by chip manufacturers; An obvious advantage of this scheme is that it is flexible and can be customized according to the characteristics of the scheme, such as snapshot and low frame rate.

(2) Adopt the front camera module.

(Machine core, such as SC11of Hitachi, H 1 1 of Sony) as image acquisition equipment, using ASIC or DSP for coding, compression and transmission. This scheme is more expensive. Because the professional imaging module is adopted, the original image effect is good, so the effect of the whole IPC product depends largely on the effect of supporting compression transmission module, and the main index is compression. In addition to the above architecture, for security vendors, how to choose a solution that conforms to their own product development direction according to different market demand and product positioning is a difficult problem for every equipment manufacturer. When choosing a scheme, the following aspects should be considered:

Storage and bandwidth usage

The improvement of image resolution will inevitably consume more bandwidth and storage space. Taking the frame of 1920X 1080@30 as an example, the coding algorithm of H.264 is used. In order to ensure the clarity, the code stream needs to be controlled at about 6Mbps, so the storage space per hour needs 2.7GB. In the ordinary LAN environment, the bandwidth of 100M can only be reliably transmitted at1.

Performance of transparent lens

The improvement of image resolution puts forward new requirements for lens accuracy and levelness control. The resolution of 2 million network cameras is ten times that of PAL system, but the technology used by ordinary high-definition DC or DV is expensive for security products, which is not conducive to the promotion of network high-definition cameras. How to lower the threshold of imaging system is a key factor in the development of network high-definition cameras.

3A control technology

On analog cameras, various manufacturers have made perfect 3A control technologies such as autofocus, white balance and automatic exposure, but the application of these technologies in digital high-definition cameras is relatively weak, and 3A control is very important for high-definition image quality. At present, there is little experience in control algorithms involved in these technical fields in China, especially in high-definition systems. The improvement of resolution will increase the corresponding algorithm overhead, so it is very important to ensure the real-time and rapid completion of these control algorithms.

Chip solution

At present, the most mainstream HD IP solution on the market belongs to Hisilicon. From Hi35 12 and Hi35 15 to the latest Hi35 16, HiSilicon provides a complete set of HD solutions. Taking Hi35 12 as an example, this scheme is a high-performance communication media processor based on ARM9 processor core and video hardware acceleration engine, which has the advantages of high integration, programmability and support for H.264, MJPEG and other protocols, among which the video processing unit can support H.264 Main Profile, Baseline, Profile, MJPEG and other protocols for encoding and decoding. Support 1.3M pixel @30fps, and support JPEG capture with a maximum of 3 million pixels; The video processing unit can also support dual code stream coding and other functions. The Hi35 12 solution has rich peripheral interfaces, which can easily meet the requirements of equipment specifications and effectively reduce the BOM cost of the whole machine. As shown in figure 2.

Front end sensor docking

In the era of analog and standard definition network, the camera CCD basically adopts the unified interface from BT.656 to CVBS, and the video compression chip can meet the problem of sensor access as long as it is connected with BT.656 chip. However, in the era of megapixels, no matter whether the front end is CCD or CMOS, each manufacturer has its own interface standards, such as LVDS and YCbCr. Even though the physical interface is the same on the surface, the internal data is different, so equipment manufacturers need to have the ability to interface with the majority of sensor manufacturers. This is also the basic homework that chip manufacturers must do before the unified digital interface of the megapixel sensor to support the diversification and industrialization of the megapixel network camera.

Coding and transmission

At present, the network bandwidth is generally 100M LAN, which has limited performance, and customers also have some considerations about the cost in use. Therefore, although the experience of megapixels is good, customers can't realize it with too high code stream at the current cost, so the coding efficiency of megapixels network camera is needed. As mentioned above, Hisilicon's compression scheme for H.264 is very mature, and it fully considers the video delay and the convenience of network packaging, etc., and can realize a 720P real-time HD solution with 2M bandwidth transmission in Hi35 12.

In addition, due to the poor internet network conditions, packet loss and delay often occur. How to ensure that video can transmit audio and video data well in the application of high-definition IP camera in harsh network environment is also a difficult problem to be solved urgently. This part depends on whether the network protocol of signal transmission of the manufacturer is robust or not, and whether TCP/UDP/ multicast and other protocols are used for data transmission, so that users can choose different protocols according to different environments.

Decoding display

It is not enough for a complete HD system to realize HD only at the front end. The whole system needs HD, including storage, management, decoding and display. At present, Hi35 15 has been released by HiSilicon, and its decoding ability is outstanding. It can realize simultaneous output of 1 VGA+ and 1 BNC, simultaneous playback of 4 channels of D 1 real-time +4 channels or simultaneous playback of 2 channels of D 1 real-time +6 channels of CIF real-time +8 channels or simultaneous playback of 8 channels of D 12 frames.

Concluding remarks

At present, all major security vendors adopt Hi35 12 and Hi35 15 chips of HiSilicon as HD IP solutions. However, due to the uneven strength of R&D and the understanding of Hess solutions, the functions of HD series products developed by various companies are also quite different. Take Ye Wei as an example. At present, the series of high-definition cameras covers Hi35 12, Hi35 15 of Haisi and the upcoming Hi35 16, providing customers with high-definition IP front-end products, such as high-definition cameras, high-definition infrared integrated machines, high-definition hemispheres, high-definition infrared high-speed balls, high-definition infrared ptz and other products. At present, Tiandi Ye Wei has 1.3 million CCD high-definition cameras. The highest resolution can reach 1280x960P, and the lowest illumination color can reach 0. 1Lux, and black and white can reach 0.0 1Lux. Support double filter day and night conversion; Support H.264/M-JPEG compression; Support backlight compensation, automatic aperture and other functions; OSD time, date and characters can be superimposed; Support two-way voice, sensitive area occlusion, video motion detection and other intelligent functions; Real dual code stream transmission can be realized. For example, the main code stream can be 720P for users to display on the big screen, and the secondary code stream can be CIF resolution, which can realize remote control and browsing. Users can browse and control remotely through mobile phones such as IPHONE4/Android/WindowsMobile. In addition, in order to meet the trend of standardization, HD series products support ONVIF protocol, and can directly connect videos through VLC and other playback software; Interface, in addition to network transmission, it can also output a BNC signal at the same time, support SD card storage, optional wifi, POE power supply and other functions.