Managing Video Quality

There is a fine balance between recording time and quality. Organizations typically want to record for as long as possible without downloading or archiving while still having the best video possible.

While for some the sole determiner may be recording time, for others it is a matter of balancing frame rate, resolution and video quality to get the best possible video for a good length of time.

With a Seon system this debate becomes a bit easier. The alarm functions can be setup to increase frame rate and quality for a specified length of time when triggered. This ensures that important moments have the best video possible while maintaining a long record time.

Resolution
Resolution is used to describe the level of detail a device can record. It usually reflects the number of pixels that are displayed horizontally and vertically. The greater the number of pixels the "sharper" the image appears.

Resolution varies based on the technology and the product. Some offer lower resolutions for efficiency, others were cutting-edge technology when they were developed and still others have the latest 2008 has to offer. Some common resolutions are:

• 350 x 240: Video CD
• 330 x 480: Umatic, Betamax, VHS, Video8
  
• 440 x 480: Analog broadcast
• 560 x 480: LaserDisc, Super VHS, Hi8
• 720 x 480: DVD, miniDV, Digital8, Digital Betacam (professional)
• 720 x 480: Widescreen DVD (anamorphic)
• 1280 x 720: D-VHS, HD DVD, Blu-ray, HDV (miniDV)

For mobile surveillance, the higher the resolution the shorter the recording time on the hard drive. Seon offers both adjustable and fixed resolution depending on the model. The Explorer DVR can be set at three different levels depending on your requirements: 720 x 480, 720 x 240 and 320 x 240. The setting is universally applied to all cameras attached to the DVR.

Frame Rate
Frame rate is the number of individual images (frames) displayed per second, which combine to make moving video. The term is often associated with video cameras and computer graphics.

A commercial movie is typically projected at 24 frames per second (fps), which is about what the average person perceives to be moving video. Commercial television is displayed at 30 FPS.

In a mobile surveillance system there is always a maximum frame rate that can be recorded by the DVR. If that maximum is 30 fps and there is one camera, that camera can be set to record at 30 fps. However, if there are three cameras they have to share the maximum frame rate, giving each camera 10 fps.

The available frame rate can also be influenced by the resolution. For the Seon Explorer model EX4 at 720X240 the maximum frame rate is 60 fps, however each camera can record a maximum of 30 fps. At a resolution of 320X240 the Explorer can record a maximum of 120 fps and each camera to a maximum of 30 fps. This is called "full frame rate recording."

Quality

Quality is the rating system of how much a file is compressed versus the amount of room it will take up on the hard drive. A higher level of quality means lower compression, and therefore a higher memory requirement.

The Quality rating system for a Seon DVR is the following:

Keep in mind these figures are only for the purpose of illustrating the differences between quality levels. The actual rates will vary with the frame rate and other factors.

By comparing the storage rate you can determine the difference in recording time. For example Quality 2 typically has three times the recording time of Quality 6 (2 Mpbs versus 6 Mpbs) because the images are more compressed.

To make sure your needs are being met, you should record sample videos at various quality levels and choose the one appropriate for your requirement

The final relationship

The relationship between recording time, quality, resolution and frames per second is a complex one. Here are a few examples for a 60 GB hard-drive:

Recording times at Quality 2 and 15 frames per second with varied resolutions:

Recording times at Quality 4 and 15 frames per second with varied resolutions:

Recording times as Quality 4 and 5 frames per second with varied resolutions:

There are detailed reference charts in Seon Manuals that help compare the three variables to make the best decision for a specific application. Seon's service department and sales representatives are available at anytime to discuss these and any other issues to make the most of a Seon Digital Surveillance System.