Technical Notes-SRT (Smart Recording Technology)
One of the most pertinant features in our system versus the competition is Smart Recording Technology (SRT). Before we go into the concept of SRT, we must first take a look at what frames per second (fps) are in a surveillance system. Keep in mind that the limits of the computer are being pushed to lay down full motion video. The pertinant factors involved are:
- The speed of the processor (CPU)
- The internal paths of the computer (BUS speed, etc.)
- The hard drive speed.
- Assuming we have an adequate computer system, the remaing limiting factor is the security system card itself, how it handles motion detection.
The speed with which it can digitize each camera image and send it to the computer then becomes the frames per second (fps) rating.
Recording Rates
There are two ways to determine the Frames Per Second (fps) on a system:
1. Total frame rate. Divide the total recording rate by the number of channels (cameras). If the total frame rate is 30 fps, and there are 16 cameras, this means that each channel will have a recording speed of 1.875 fps.
2. Adjustable frame rate. Some manufacturers, including us, offer an adjustable frame rate. This helps with better frame rate utilization of your system. For example: Suppose we are using the same system as example one: 30 fps with 16 cameras. Now with this adjustable system you can set each camera to the desired frame rate, but the sum still must not exceed the maximum frame rate for the system (30fps for this example). Pick your four most pertinant cameras, set them to 5 fps each (for a total of 20 fps), and you would only have 10 fps left to be divided amoung the remaining 12cameras. This equates to a bit less than 1fps per camera on cameras 5-16, which may be just fine if your subjects are not in high motion. If you are recording money counting, cars in fast motion or other "high" speed activities, you may need to look at purchasing a higher frame rate system, or read on about SRT.
Both systems have their advantages and drawbacks. In example one, you have no control over the frame rates. It is evenly divided amongst all cameras. It may be too slow on some cameras and more than adequate on others. In the second system, Murphy's Law will most likely apply, incidents will always seem to happen where the frame rate was set to the lowest speed. Naturally you will miss something important while your high speed cameras may not even be recording! Now, we have a solution for this problem. It is called Smart recording technology (SRT).
What is SRT?
SRT allows our system to automatically allocate recording frame rates to locations as they are needed (something in motion). Keep in mind our high end systems are capable of up to 120 fps without SRT, so with SRT you can realize frame rates that leave the competion way behind. Our SRT capable systems can make our 30 fps system perform like a 120 fps system, and our 120 fps system is capable of nearly 120fps on one camera, even though it has up to 16. Thus, it behaves as though it were a 480fps system when the motion is limited to one camera, a little less as each camera is detecting motion. We are able to do this by allocating the better part of the frames per second to the camera(s) "seeing" something in motion. The computer automatically assigns the most frames per second available to that camera or cameras. The result is more pictures of your target, more chances to see what transpired, and a better chance at achieving your desired result.
With SRT you may select one of the following three options:
- [Auto]: SRT enabled. When a camera is set to [Auto], the system will automatically allocate as many frames as possible to this camera when motion occurs. If this option is selected, you will not need to set [High] or [Low] (described below). SRT will only be in effect after you start recording, nothing will be perceived in Preview mode (live view on the local sever screen). This is the best option for most situations where there is random activity on the cameras.
In the rare instances that you have motion on all cameras simutaineously on a regular basis, please read the descriptions below.
- [High]: The system will force a high percentage of frames (not a pre defined frame number per second) to this camera, then it will give the remainder of available frames to the system sharing between the other cameras. Assuming that all cameras are detecting motion simultaneously, you will be assured that the cameras set to [High] always receive more frames per second than the cameras set to [Low]. But you will not be stuck with a pre defined frame rate. It will give the most frames available to the camera with the motion detected. You will see the effect in both in preview mode (what is on your server's screen) and on the recorded video.
- [Low]: The System will reserve a low percentage of frames for the cameras with this setting. Assuming that all cameras are detecting motion simultaneously, the cameras that are set to low will relinquish frames to the cameras set to [High].
