It is apparent to any law enforcement or security officer that more crimes are being caught on video, making additional evidence available from these tapes. One of the main reasons for this development is the proliferation of security cameras. As homeland security efforts take center stage, more security cameras are being installed in public spaces. Also, the costs of video surveillance systems are now within reach for small businesses. Previously only in the domain of deep-pocketed organizations, less prominent retailers can now afford to have their businesses wired for video surveillance. This capability can provide unparalleled insight and protection; however, there are many common sources of degradation that can be frustrating to security personnel.
Because video surveillance footage can hold the key to solving a crime and degradation can undermine the quality of the video, widespread camera usage has resulted in an increased need for video analysis and enhancement by technical investigators – enabling them to unlock critical details that might previously have been lost without analysis tools. Fortunately for investigators, advances in the processing power of personal computers now give them the ability to use simple computer-based digital video capture and editing systems to enhance and clarify video content.
Before engaging in video clarification, a technical investigator should understand the most common sources of video degradation. Degradation can be caused by environmental sources, video camera quality and type, the transmission of the video signal from a camera to the recorder, the video recorder quality and the actual tape from which the video signal was recorded. These sources create various effects that impede the technical investigator’s ability to create an accurate, detailed image of the recorded scene.
The most common causes of video degradation, outlined in Figure 1, are atmospheric effects, noise, motion blur, out-of-focus blur, low image resolution, low signal bandwidth and tape and wear stretch. With some planning, careful installation of equipment and the implementation of video enhancement tools now specially designed for law enforcement and security personnel, these common pitfalls can become a thing of the past.
Even the heat of the circuitry in a camera generates its own white background noise called thermal noise. For low-light images, some external forces can create random variations of electric charge on video camera’s charge-coupled device (CCD), thus creating snow in the image. White noise can become particularly disruptive and more apparent when the video is amplified to the desired viewing level. So one might particularly encounter this issue when scouring video for the details, the very time that it is most important to see clearly. That is why video enhancement is so critical. Video forensics software enables security professionals to negate noise by using frame averaging to create a clearer composition.