DVR records to a hard drive. Each frame of captured video has a size ranging from 0.5k to 15k depending on the resolution and recording scene. A second of video has a range from 1FPS to 30FPS depending on setting. The size of the video is then decided of its length. Overall, the total size of the video file is ultimately decided by the length and quality. Videos on TV have a frame rate of 30FPS. Although a lower FPS may yield a lower detail of the recorded event, a rate of 7.5 fps is sufficient for most activities, while a rate of 15 fps is sufficient for recording hand movement on cash counters and car license plates. The need of quality is related to the circumstances in which the recording takes place. As videos are being saved onto the hard drive, hard drive slowly loses its capacity for newer videos for storage. Once the hard drive is almost full, software installed in DVR will save the later videos over the oldest, creating a first in first out cycle. The size of the hard drive will be the determinant of how long a video can be saved before it is deleted. However, since the length of video that can be saved onto the hard drive is also depended on the quality, it is difficult to determine the exact length of saved video. Hard drives range from 100 GB to 1TB and the total recording length may range from half a week to one month. It is then up to the customer’s needs for a larger hard drive.