China's Safe City projects are pushing development of DVR products as well as providing a better platform for manufacturers to improve technology and product features.
New digital video recording technology is making security officers' jobs a lot easier as they no longer have the hassle of changing tapes. Meanwhile, Chinese manufacturers are coming out with standalone DVRs that feature different operating systems and compression algorithmsmainly MPEG-4 and H.264.
Looking back over the history of DVR development in China: from 1999 to 2003, local DVR makers adopted MPEG-1 compression board products (Thakral); from 2002 to 2004, some board and software suppliers shifted to MPEG-4 standalone DVR development (Tmvideo and Chenova); in 2006, leading suppliers (BlueStar, Chenova, Dahua, Dali, Hanbang, HighEasy, Hikvision) drew a lot of attention internationally for their outstanding products using MPEG-4 and H.264 compression, and advanced resolution from CIF to D1.
According to Rocky Ran, Technical Manager of Tmvideo, "There are two basic types of compression boards used in digital recorders: software and hardware compression. Most DVR systems use the latter since they are designed to capture video and convert analog to digital. Once captured and converted, the data is sent to the DSP or SoC where it is compressed." Since these products cost more, they are used for mostly large projects.
"In China, 90 percent of board suppliers sell hardware compression boards as they provide greater flexibility for project-based integration," pointed out, James Wang, Overseas Product Manager of Dahua.
"Software compression boards," said Xiaodong Liu, General Manager, Beieot, "are based on core chipsets, which process captured images, and other hardware structure, which is on the main board. These products look the same since the electrical and chipset layout corresponds. These compression boards adopt image capturing chips (Funsion 878A) and data is sent to system CPUs for compression."
Zhangbiao Mao, General Manager of Wave-p, a software compression board manufacturer, agreed, noting that software compression boards can satisfy the needs of small applications, which require mainly plug-play products.
Chinese suppliers, said Ben Lo, Director of SOE, are good at hardware compression. Distribution channels for these products, however, are different from standalone; most distributors like standalone products even though profit margins are lower because they require less service and training of installers and end-users. Given the need for scalability, the software package has to be equally good, he stressed, to support medium-sized applications. That is why board suppliers provide SDK for customization.
"When users require weeks of storage, they need a system capable of archiving gigabytes of video with the best compression technologies available," said Yuxiao Chen, Vice President, Security Business Unit of Coship, which manufactures standalone DVRs, cameras and mobile DVRs. In fact, its mobile DVRs have already been installed on 1,062 Chinese buses.
Storage costs, he emphasized, are significantly higher (even though HDD prices are dropping) if video is compressed using the wrong algorithm. In more advanced systems, video data is compressed more efficiently, thus taking up less storage space.
To choose the most suitable DVR product, users should first determine if it is to be used for remote monitoring or local recording. For the former, compression algorithms must be used to enhance available network bandwidth so remote viewers get the best images at proper frame rates. For local recording, compression algorithms should be used to enhance available storage. If sufficient storage is available, then compression parameters can be set higher for better quality video.
DVRs are typically designed around either JPEG or MJPEG compression. These compression methods differ significantly in terms of how images are processed, affecting both throughput capability as well as image quality. MJPEG-based methods currently top out at compression ratio of around 200:1. The net result is smaller file size; this directly affects storage requirements and performance as well as remote communications requiring image transmission. Some suppliers provide economical MJPEG products to satisfy basic surveillance needs. "With H.264 compression, the parameters meet the needs of both remote monitoring and local recording, but the cost is higher," said Shende Cai, Technical Manager, NeaTech.
Most users prefer to work with existing networks to avoid spending money on upgrading or expanding networks. Network system has to be able to cope with large quantities of information, multiple users working in a multi-site environment and an increasing amount of video that need to be moved onto the network at frequent intervals. This must all be accomplished with minimal bandwidth.
Chinese makers are, therefore, using the latest algorithms, mostly MPEG-4 and H.264. Given the advantages of H.264 in terms of transmission and huge demand from banks, suppliers are increasingly focusing on this algorithm.
Operating Systems and External Storage
The three major operating systems in Chinese DVRs are Linux OS, Vxworks and RTOS, though the trend is toward greater use of Linux-based DVRs. External ports for standalone DVRs require USB or HDD ports, which are either IDE or SATA. USB is divided into USB1.1 and USB2.0. Manufacturers stress that USB2.0 and SATA HDD ports benefit from higher transmission speeds.
Linux-based DVRs possess powerful functions and GUIs that are better than RTOS plug-play OSD menus. The common features of Linux-based DVRs are channel-setting copy, two to four schedule recording setting, smart event searching (from time search to type list), HDD dormancy mode, USB2.0 for external backup devices, mouse control or keypad, and dual-stream setting.
Before widespread deployment of the Internet, traditional DVRs were mainly used for recording, storage and convenient event backup; now, requirements are much higher for storage size and transmission speed. "Our standalone DVRs," said Lo, "support eight built-in HDDs; the models with removable HDD trays or built-in CD/ DVD-RW are very user-friendly." Moreover, "built-in CD/DVD-RW designs cost more," said Cai. "Chinese suppliers are making DVRs with USB ports for external backup devices, including flash memory stickers, HDDs and CD/DVD burners."
Local Recording vs. Remote Surveillance
Uncompressed video needs a tremendous amount of disk space, so vendors employ various compression schemes from dual stream to dual codec, combining both still and dynamic compression schemes to meet network environment and storage requirements.
New processors support dual streaming, allowing both monitoring and recording streams for every video channel. Dual streaming is critical for digital video applications since high-quality streams recorded to hard-disk drives (HDD) or networkattached storage (NAS) require different processing than lower quality monitoring streams intended for immediate viewing in the security control booth.
"What these cards do differently is to record the first data stream at 320 x 240 CIF, doing so at 30 frames per second for eight channels (total 240 frames per second). The second data stream goes to the scaler where it is reduced to 160 x 120, but it maintains real-time frame rates. So file size for network transmission is reduced, thus allowing the DVR to deliver a faster frame rate to the remote monitor. Of course, quality of remote images might be less than acceptable, but it ensures real-time remote surveillance," explained Mao.
Other groups are working on dual codecs like wavelet for local recording and H.264 for network transmission to ensure smooth remote transmission and good local recording without mosaics.
Take TVT's new H.264 model. According to TVT General Manager, Mike Kwo, it is designed to satisfy both local recording and remote monitoring needs. It supports dual streaming, achieving VCD image quality with bandwidths of 383 kilobits per second. SoC combines CPU, DSP and hardware enhancers for system efficiency. It also features channelhidden settings, remote configuration, playback, loading and backup via Internet, FTP and USB stickers for software updates, and system log lists for better view and efficient search.
Storage vs. Resolution
A common misconception is that 4 CIF is preferable in all environments. The primary consideration, however, when choosing a DVR is storage capacity. Storage requirements are governed by a number of factors, including quality of cameras and resolution, recording speed, compression method, and continuous or event-only recording.
Most Chinese DVRs provide D1 resolution for live, full-screen viewing but CIF to D1 (optional) configurable for recording, said Mao. Resolution depends on what is recorded. "If you simply want to capture an image of a car in a parking lot using an analog camera, for example, one CIF will do. With one CIF, you would be able to determine if there is a vehicle in the camera's view, but would not be able to capture finer details, such as the license plate number. Two CIF should be used to record more detailed images, such as a license plate number or a person's face. However, two CIF also requires twice as much disk space so it is important to take those storage costs into consideration. Besides, users can configure recording speed or set alarm recording as needed to save HDD space."
Frame rate, compression, storage and scalability are important for standalone DVRs. "Multi-channel playback, intelligent search functions and three-dimension positioning are good features," said Wang.
Searching for a particular recording incident is much easier now with DVR systems. With rapid development of HDD technology, greater storage and external RAID systems, intelligent searches from those based on time, event list and type to calendar and table enable users to easily view video clips. NeaTech DVRs, said Cai, provide jog switches for quick searches that save a lot of time. In addition, the products allow users to view video from remote locations using standard web browsers.
In the event of a security breach, video clips showing criminal activity are exported to a CD-ROM and handed over to local authorities for prosecution. "The DVR system, pointed out Shuhua Wu, Product Manager of Kocoda, "features a built-in video authentication process, which automatically verifies that stored video data has not been edited since it was archived with a watermark. This feature is extremely important as video clips must first be proven to be original and unaltered before they can be used as evidence in any court proceedings."
It is a good idea to ask potential DVR vendors what storage options are available. DVRs provide a certain amount of internal hard drive space, but generally not enough to store a large amount of video, not to mention the higher power consumption and heat generation from groups of HDDs, which may have a negative impact on the system. It is important to plan for offline storage and retrieval as well. Some companies make backup copies and store them at an offsite location such as an NAS setting.
As the industry has slowly moved toward IP-based devices, enterprises will have the option of purchasing IP cameras that send compressed files via IP to storage devices on the network. Users will be able to leverage existing computer network infrastructure to save on installation. Network-based storage solutions can be a viable solution for an application demanding large amounts of archive capacity as current HDD technology is rapidly advancing total available storage capacities as well as disk performance and reliability.
Optional file export devices, such as CD-RWs or DVD-RWs, are expensive if users want to ensure that they have the capacity to match storage found on typical DVR internal disk arrays. Considerations regarding available network bandwidth and specific DVR support of network-based storage will factor in the application of networkbased archives, said Wang.
"DVR configure privacy areas with mosaics," said Lo. "This idea came from ATM DVR models. In order to protect ATM user passwords, security officers can set mosaic areas on keypads of ATM when DVRs are recording. We use the same concept with standalone DVRs to give users the flexibility." In some countries, however, positioning cameras toward keypads when users are typing passwords is forbidden.
With digitization, CCTVs are shifting toward IP-based, intelligent, cross-platform system management and customization. The hot products are now DVS, IP cameras and hybrid DVRs. That said, DVRs retain an unshakable position since they combine features of DVS and huge storage space. Besides, new equipment and better IP environments come at much higher costs than existing analog cameras used together with DVRs.