Evaluating digital video surveillance.Last Spring, another tenant on our floor came to our office seeking help. David, a sales manager sales manager n → gerente m/f de ventas
sales manager n → directeur commercial
sales manager sale n → for a telecommunications company See telecom company. was concerned about a recently hired salesperson. Eric's sales performance was well below expectation.
Eric had not given straight answers about his past sales activities and David suspected Eric was exaggerating his selling efforts.
Arriving at work that morning David hadn't seen Eric in the office but noticed that his computer was still on and hoped that he might be on a sales call. Eric returned around 11:30 explaining that he had come in 8:00am, and worked for an hour before leaving for a sales meeting sales meeting n → reunión f de ventas .
Knowing that we are in the security business, David correctly guessed that the video cameras in the elevator lobby on our floor belonged to us. With building management's permission we had mounted cameras in the elevator lobby for our technology evaluation program and been recording all activity in the lobby for several months using an advanced digital video recorder See DVR. (DVR (1) (Digital Video Recorder) A device that records video onto a hard disk from one or more ceiling mounted video cameras. Part of a security system, the DVR typically supports 4, 8 or 16 separate camera channels. ).
After logging onto the DVR web site it took only about 5 minutes to review every video sequence from the elevator lobby camera from 7:00 am to the video clip A short video presentation. showing Eric's arrival at 11:18 am.
With irrefutable irrefutable - The opposite of refutable. video evidence that Eric had lied, David did not hesitate to dismiss Eric that afternoon saving the company $3,000 per month in base salary and much more in lost sales opportunities.
Although closed circuit television (CCTV CCTV
CCTV closed-circuit television ) has been around for decades, recent advances in digital technology have made managing the recorded material much more convenient.
A surveillance DVR is very similar to consumer products like Tivo and Replay that have replaced VCRs in many homes.
Like their consumer-grade cousins, surveillance DVRs convert analog television Analog television (or analogue television) encodes television and transports the picture and sound information as an analog signal, that is, by varying the amplitude and/or frequencies of the broadcast signal. signals (from cameras) into bytes of data which are stored on a computer hard drive as video files.
These files can be duplicated, emailed, downloaded, searched and reviewed like any other data file on your computer, making them far more manageable than video tapes.
Hundreds of DVRs are available today from well-known companies like Pelco, Kalatel (General Electric) and Panasonic as well as from many small, more specialized manufacturers. Most DVRs are designed to simultaneously capture and store video from 4 to 16 cameras.
Typically, they will also allow viewing of live and previously recorded video from multiple cameras without interrupting the more critical recording process, Prices for an 8 or 9 camera DVR currently range from $2,000 to $5,000. The more expensive models offer more storage for video archives, higher video frame rates, programmable video motion detection, computer network compatibility and a growing list of other sophisticated features.
When evaluating DVRs for purchase, management should consider the following four questions to narrow down the field of options:
1. How many cameras? Most DVRs can be configured for 4, 8/9 or 16 cameras. Consider both your current needs and near term expansion requirements.
2. What frame rate? Frame rate is an important measure of video quality. Surveillance applications usually require only 2.5 to 7.5 frames per second (FPS (Frames Per Second) The measurement of full-motion video performance. See frame.
fps - frames per second ) compared to 30 FPS for entertainment quality video. A DVR's total frame rate should be at least equal to your required frame rate per camera times the number of cameras. If the DVR specifications are quoted in "Fields per Second" you will have to divide by two to determine the total "Frame" rate.
3. How much storage? Calculating the video storage capacity of a DVR can be complicated. The size of the hard disk only provides half an answer. The more important measure is frame size. A standard surveillance frame measuring 320 x 240 full color pixels can require anywhere from 4,000 to 50,000 bytes of storage depending on both picture quality and data compression data compression
Process of reducing the amount of data needed for storage or transmission of a given piece of information (text, graphics, video, sound, etc.), typically by use of encoding techniques. . Smaller frame sizes provide more days of storage per gigabyte, but may sacrifice quality. Look for DVRs with MPEG (Moving Pictures Experts Group) An ISO/ITU standard for compressing digital video. Pronounced "em-peg," it is the universal standard for digital terrestrial, cable and satellite TV, DVDs and digital video recorders (DVRs). 4, the latest industry standard for video compression Encoding digital video to take up less storage space and transmission bandwidth. See video codec and data compression.
video compression - Compression of sequences of images. that offers the highest high quality, most data-efficient video.
4. How much bandwidth? Most surveillance DVRs can be connected to a computer network for both on-site and remote access.
Because video files are relatively large, remote access to live cameras and to video archives require broadband connections both at the surveillance site and at the remote viewing site. Although broadband networks are now widely available, monthly fees can be expensive particularly for higher bandwidth connections.
DVRs that use efficient video compression such as MPEG4 will help save money on network costs since they can use lower bandwidth connections to deliver the same number of remote video streams as less efficient systems.
Selecting the right DVR for your surveillance needs is not simple. If management plans to make a significant investment, they would be wise to seek the help of consultant or integrator with a thorough understanding of digital video processing, data storage management, network design and software engineering.
Because most of this knowledge is computer related, your best advisor may be one with both computer and security experience.