10-25-2007, 11:19 AM
What is Video?
Video is an accurate visual representation of some event. The visual representation is normally created through the use of a video camera. The camera converts the image it views to an analog voltage. This analog voltage (video signal) can be transmitted via wire (coax), or RF (Radio Frequency) to be remotely viewed on a television monitor. Uses of video can range from entertainment, to education, to security. In the security industry video is used as a tool for viewing and recording events and as a deterrent to deviant behavior.
How is the Video signal generated?
Video cameras make use of a device called a CCD (charge Coupled Device). The CCD is an array of more than 300,000 very sensitive light detectors, in an area of less than one-quarter Inch Square. These detectors, when struck by light focused on the CCD by the camera lens, create a small charge. The CCD then transforms this small charge into what is commonly known as the video signal. The video signal is then transmitted via some medium to a receiving device-such as television monitor-where it is again translated back into a video picture for viewing.
What is Compression and why is it needed?
To create digital video, the video signal generated by the video camera must be transformed from the analog voltage to a digital representation. This is accomplished through a process called Digital Signal Processing (DSP). Once the conversion from the analog signal to the Digital representation is complete, the video can be stored on typical computer media such as a hard drive. If the digital representation was stored exactly as converted, the data storage required would be in excess of 21 Megabytes per second. A typical CD can hold 670 Megabytes worth of data-which is less than one minute of video. This leads to the use of compression techniques. (Analog Devices) Compression is the technique of storing video images in less space by removing unnecessary data. Through the use of compression you can decrease the amount of storage required for the video images without losing video quality. The CD that would originally hold less than one minute's worth of video can now hold a full-length movie when the video is compressed. In most cases it is desirable to remove as much information as possible without degrading the visual reproduction of the image.
What is Wavelet Compression?
Wavelet is the newest compression technology available on the consumer market. The following excerpt from Analog Devices Wavelet Signal Processing Technology white paper describes how the compression works.
Wavelet technology enables digital video to be compressed by removing all obvious redundancy and using only the areas, which can be perceived, by the human eye. The human eye cannot resolve high frequencies. This is analogous to humans not hearing high frequency sounds, a dog whistle is an example of such a product.
Wavelet technology filters the entire field or each frame at once. This approach results in no blocky artifacts or clunky images. Wavelets 'gracefully' degrade the picture quality as the compression rate increases. In addition, Wavelets enable precise bit rate or quality control of the images and a built in error resilient bit stream. The end result is a simple, efficient software implementation. The designer is able to control and to specify the compression rate for the video application under consideration. Broadcast rates are low ratio compression rates which are memory intensive, while security applications employ high compression rates to enable weeks to months of video to be stored.
Video is an accurate visual representation of some event. The visual representation is normally created through the use of a video camera. The camera converts the image it views to an analog voltage. This analog voltage (video signal) can be transmitted via wire (coax), or RF (Radio Frequency) to be remotely viewed on a television monitor. Uses of video can range from entertainment, to education, to security. In the security industry video is used as a tool for viewing and recording events and as a deterrent to deviant behavior.
How is the Video signal generated?
Video cameras make use of a device called a CCD (charge Coupled Device). The CCD is an array of more than 300,000 very sensitive light detectors, in an area of less than one-quarter Inch Square. These detectors, when struck by light focused on the CCD by the camera lens, create a small charge. The CCD then transforms this small charge into what is commonly known as the video signal. The video signal is then transmitted via some medium to a receiving device-such as television monitor-where it is again translated back into a video picture for viewing.
What is Compression and why is it needed?
To create digital video, the video signal generated by the video camera must be transformed from the analog voltage to a digital representation. This is accomplished through a process called Digital Signal Processing (DSP). Once the conversion from the analog signal to the Digital representation is complete, the video can be stored on typical computer media such as a hard drive. If the digital representation was stored exactly as converted, the data storage required would be in excess of 21 Megabytes per second. A typical CD can hold 670 Megabytes worth of data-which is less than one minute of video. This leads to the use of compression techniques. (Analog Devices) Compression is the technique of storing video images in less space by removing unnecessary data. Through the use of compression you can decrease the amount of storage required for the video images without losing video quality. The CD that would originally hold less than one minute's worth of video can now hold a full-length movie when the video is compressed. In most cases it is desirable to remove as much information as possible without degrading the visual reproduction of the image.
What is Wavelet Compression?
Wavelet is the newest compression technology available on the consumer market. The following excerpt from Analog Devices Wavelet Signal Processing Technology white paper describes how the compression works.
Wavelet technology enables digital video to be compressed by removing all obvious redundancy and using only the areas, which can be perceived, by the human eye. The human eye cannot resolve high frequencies. This is analogous to humans not hearing high frequency sounds, a dog whistle is an example of such a product.
Wavelet technology filters the entire field or each frame at once. This approach results in no blocky artifacts or clunky images. Wavelets 'gracefully' degrade the picture quality as the compression rate increases. In addition, Wavelets enable precise bit rate or quality control of the images and a built in error resilient bit stream. The end result is a simple, efficient software implementation. The designer is able to control and to specify the compression rate for the video application under consideration. Broadcast rates are low ratio compression rates which are memory intensive, while security applications employ high compression rates to enable weeks to months of video to be stored.