How Digital Video Recorders (DVR's) Are Made

There are actually two kinds of DVR's: the PC based kind, and the proprietary kind.

We focus on the PC based DVR's, because we believe they have key advantages over proprietary DVR's and are more cost effective in the long run.

Proprietary DVR's

With a proprietary DVR, the DVR is made by a major electronics manufacturer and is only support by that manufacturer, they will not allowed users to have access into operating system or the manufacturer's software.

The proprietary DVR is a "black box". It doesn't open up, and the electronics inside can be anything. The way the DVR works, and the capabilities it has, are fixed and determined by the electronics vendor.

The disadvantages of a proprietary DVR are:

• It typically has less capability than PC-based DVR's.
• PC-based DVR's generally have much greater software capability as well.
• Since it is not PC-based, it may use its own proprietary compression systems and video file formats, incompatible with the rest of the world.
• With PC-based systems, you can always trade video files with police or anybody else who you want to share them with.
• If it breaks, it has to be shipped back to the original manufacturer. It cannot be repaired by a local shop. Any PC-based DVR system can be repaired by a good PC repair shop. We warranty PC-based DVR's that we sell for one year.

For these reasons, we focus on PC based DVR's, in particular the Trident Video System DVR. We believe that even though they are more expensive at first glance, they are cheaper in the long run, when you take into account everything they can do, and all the reliability and support issues.

PC-based DVR's

A DVR is actually a special kind of computer. We know computers are not always easy to use. Your DVR has its own special user interface that makes it easy to use.

Just like a PC, a DVR starts off as a case with a PC motherboard and power supply. Stay away from DVR vendors that use "workstation" power supplies, because they are designed to be shut off at night. We use a high-quality server power supply, which is designed to run 24/7.

An Intel processor is used as the brains of the system.

The memory used is standard PC memory.

Hard drives are added for storage. The hard drives and the fan are the only moving parts in the system, and the parts most likely to break. We use only reliable, high-quality fans and hard drives.

Then special video capture cards are added. These cards contain advanced digital signal processing technology.

A Trident Video Security capture card.

Here's the job the video capture cards do:

• Capture the video images from the coaxial NTSC BNC connectors.
• Compress the video using the MPEG-4 video compression algorithm.
• Transfer the video from the video capture card to main memory. The card cannot write the video straight to disk because of timing reasons. The disk drive has to move the read/write head to the proper location before the video can be written. Once in main memory, special software will take over to move the video to disk.
• And decompress recorded video for playback.

Here is another little secret for you. The video capture cards are described in terms of their shared frame rate. The shared frame rate refers to the total frame rate of all the cameras on the system. This is very confusing to non-experts. Most people would expect the frame rates to refer to the number of frames per second you get on each camera. Because if you have 30 frames per second, that's great for 1 camera, fine for 4 cameras, but pretty bad for 16 cameras -- for 16 cameras, that means each camera has only 1.875 frames per second. But this was not intended to be confusing. It is done this way for historical reasons. Before the days of DVR's, people used VCR's to record video. In fact, maybe that's what you're doing right now, if you haven't bought a DVR yet. The VCR is used with a multiplexer that combines the video from multiple cameras into a single video stream. So if you have 4 cameras, you can record them all on one VCR with a 4-camera multiplexer. If the multiplexer and VCR handle 30 frames per second, you will get 7.5 frames per second from each camera.

The video capture cards themselves are manufactured using semiconductor fabrication technology. They are made the same way that all other computer chips are made.

For the Trident Video Security system, the operating system is Windows XP Professional, and the special Trident Video Security user interface (GUI) is installed on top. To use a Trident Video Security DVR, you do not need to know much about how to use Windows XP Professional itself. You only need to know how to use the mouse, and how to use the Trident Video Security software. The only complex part of the Trident Video Security software is the camera and I/O configuration screens, which your installation technician will take care of for you.

The main Trident Video Security configuration screen.

You only need to deal with the user interface for watching your cameras, recording, and playing back video.

The Trident Video Security software screen.