“High-end applications will tend to require very large storage capacities, advanced networking capabilities and options available to support unique integration, such as audio and data capture,” says Carl Bracken, central region sales manager, Sanyo Security Products.
Peter Wilenius, vice president and general manager of video solutions, March Networks, Ontario, Canada, points out that the return on investment (ROI) is also notable. “The ROI can be measured in reduction of travel for both service technicians and investigators, reduction in retrieval time and cost and reduction in overall cost of system for long-term storage.”
“Specific ROI calculations can get complicated and vary from installation to installation. Advantages of high-end digital recorders make return on investment for systems much higher than at first glance. Over time, the benefits from increased personnel productivity, asset and personnel protection, lawsuits not filed and the emerging advantages of video content analysis to the bottom line all combine to create a favorable return on investment,” says Jonathan Moav, director of product marketing for NICE Systems, Rutherford, N.J.
Most low-end systems are multiplexers that record either a limited number of channels (one or two) at a high frame rate, or more channels at a significantly lower frame rate (16 channels at 1-2 fps). High-end systems can accommodate a large number of channels at a high frame per second (fps) recording rate—tens of channels at 30 fps real-time, suggests Moav.
“While low-end DVR units are capable of attaining high frame rates, it is usually at the expense of the other inputs on the unit. High-end DVR, enterprise-level systems are able to attain high frame rates on all inputs simultaneously and can distribute the frame rate variably across the inputs,” says Peter Wilenius, vice president and general manager of video solutions, March Networks, Ontario, Canada.
Storage Necessities
Lower-end DVR systems tend to have a fixed limitation in the amount of storage that can be contained within the unit itself. At the higher-end, the systems tend to have a higher capacity internal the unit and also have the ability to connect to large external storage devices, says Wilenius.Transferring video locally to CD-RW or similar media sparks visions of the VHS dark ages. According to Wilenius, the best solution today is to keep the video stored at the remote site on high availability RAID disk arrays.
Current HDD (hard disk drive) technology is rapidly advancing total available storage capacities, as well as disk performance and reliability. Current HD’s form the backbone of the primary storage found in virtually all-industrial DVR’s currently on the market. Optical media, such as CD-R/RW, DVR-R, DVD-RAM, currently lack the capacity to match the storage found on the typical DVR internal disk array. Tape-based archival solutions such as DAT, can match up to some of the smaller DVR capacities, however, tape-based back-up options can present a challenge due to the time required to archive a large storage volume. In addition, tape-based archival typically requires a full-restore process in order to review the stored image data. Network-based storage solutions can be a viable solution for an application demanding large amounts of archive capacity. Considerations to available network bandwidth, and specific DVR support of network-based storage will factor in to the application of network-based archival, says Bracken.
System Scalability
“Low-end DVRs are usually stand-alone, off-the-shelf systems. The high-end systems are typically constructed to meet exact specifications and can be integrated with other security applications such as access control, fire and various other alarms and databases,” says Moav.
“With a networked digital video system, integration with existing databases, such as financial institutions or even an access control system, becomes a reality. The ability to associate video with existing data, and search based on that data, provides additional benefits to customers,” says Wilenius. And these units are configurable and maintainable from a central location.
Compression Schemes
“When talking about weeks of storage, you want a system that is capable of archiving gigabytes of video with the best compression technologies available,” says Jon Williamson, product marketing manager, Andover Controls, Andover, Mass. The best compression method to select is one that will allow the user to tune the system to best meet their needs. Cost of storage is significantly higher if the video is compressed using a less sophisticated algorithm. With compression algorithms used in high-end systems, the video data is compressed more efficiently taking up less storage for the same time period.The user must first decide the main function of the DVR; remote monitoring with video transmission or local recording. If used primarily for remote monitoring, the compression algorithms must be tuned to best utilize the network bandwidth available so the remote operator can get the best image at a manageable frame rate. If local recording is the primary function of the DVR, then the compression algorithms would be tuned to utilize the available storage in the most efficient way. If sufficient storage is available, then the compression parameters could be set such that high quality video would be stored. With H.263 compression, the parameters can be tuned to meet the needs of both remote monitoring and local recording. Higher-end processors can support compression schemes that both compress the video to a smaller amount of data and allow the video to decompress more efficiently.
Industrial DVR’s currently are typically designed around either JPEG/MJPEG- or Wavelet-based compression methods. These compression methods differ significantly in how images are processed, impacting both the throughput capability as well as image quality. Wavelet-based image compression can easily produce a 400:1 ratio while MJPEG based methods currently top out around 200:1. The net result for comparable image quality is a smaller file size for each frame of video; this directly impacts the storage requirements and performance as well as remote communications requiring image transmission, offers Bracken.
Most users want to utilize their existing network and avoid spending money on upgrading or expanding the network. This has become a hot topic, as the network system has to be able to cope with large quantities of information, multiple users working in a multi-site environment and increasing amounts of video that needs to be moved on the network at frequent intervals. This all must be accomplished with minimal bandwidth pressure, says Moav.
