What You See Is What You Get

Why are the images during a CCTV playback so different from images during live view? That is a common question raised particularly when you are trying to identify the suspect from the recorded video. The sad truth is, in most cases, it's not - particularly in the playback mode.

DVR Video Capture Card

DVR stands for Digital Video Recorder and what it comprises is a black box that take in analog video signal from cameras, convert and digitized that signal for storage on the hard disk.

In order to record and hence playback good quality image, we need to start with ensuring that we have a reasonable camera capturing images under adequate lighting.

Recording Frame Rate

Once that is taken care with, we must then consider the quality of the DVR's video capture card. The Video Capture Card performs the conversion of analog to digital and is often specified in terms of its frame rate, the image resolution and the compression method.

To digitize the video, the Video Capture Card takes the analog video, and broke it into different frames, digitizing one frame at a time. Hence a Video Capture Card that is specified 25 frames per second (fps) can process at the most 25 frames per second. If this card is connected to 4 cameras, the maximum frame rate per camera will be 6.25 fps. This frame rate will affect the quality of the playback.

Display Frame Rate

A different circuitry (either on the same video capture card or on the mother board) is used to display the video signal to the monitor. The quality of the display is, like video capture, measured by its frame rate. The recording and the display frame rate need not be the same. In fact, more often than no, the display frame rate is higher than the recording frame. Which is why the images appears better when view live,

Video Compression

To save on hard disk space, the data after conversion is compressed. With compression, certain image details such as sharpness or richness of color will be affected, resulting in a difference between what you see live and what you see at playback.

Viewing over Network and Internet

Depending on the DVR, there may be a marked difference between the playback images at location versus viewing them over the network and the internet.

Streaming over the internet or network is heavily dependent on the traffic and bandwidth. Hence, to ensure that they can still deliver images even over the internet, some DVR employs a higher compression ratio. Meaning the data is packed even smaller so that it can get down the internet to your computer, resulting in poorer images than what was viewed at location.

Will things get getter?

The world is moving towards greater digitization, resulting in better data compression algorithm being developed and tested. The DVR since its inception has gone through tremendous changes, and what we are seeing is the development of better algorithm that is packing the video data smaller, with better resolution.

The future is bright, and yes, the image should be better, brighter and sharper with the newer range of DVR