DVR and NVR

Digital video recorders (DVRs) are recorders which convert video into digital format and store them on hard disk drives. Compared to video cassette recorders (VCRs), DVRs offer better image quality, longer recording time, easier configuration, simultaneous recording and viewing and advanced recorder video search capabilities and remote monitoring. All DVRs come with a built-in multiplexer which allow multiple cameras to be viewed on a single screen. Other features to look for when you are buying a DVR include:

• Frame rate - the higher the frame rate of the DVR, the more responsive it is to motion. Frame rate is divided among the number of video inputs of the DVR. If a DVR has 4 video inputs (i.e. it can record up to 4 cameras at a time) and its framerate is 60, then video for each camera is recorded at 60/4 = 15 frames per second.
• Compression - the better the compression of the DVR, the longer the recording time. At present, the best compression is H.264 followed by MPEG4.