Motion detection vs. continuous recording – Pros and Cons

Nowadays almost all the security systems are able to record on two modes: continuously (24 hours non stop) or based on motion detection. When you set your system to record 24 hours, the recorder will store the footage continuously on your hard drive using the framerate, resolution and bitrate specified on the settings of your recorder. Compared with motion mode, recording continuously 24 hours a day will give you less recorded days on the hard drive.

Both motion and continuous recording work by using the H264 compression. Unlike 24 hours recording, motion recording does not record unnecessary events. Using H264 standards, motion detection works by comparing the frames one by one and subsequent changes in the image. Since H264 ignores the stationary objects, house, stationary car or tree in the images, and only uses changes in the motion-blocks in the frames for recording, motion detection saves both bandwidth and recording storage. When you are using motion recording, security systems are always recording in the background as buffer. Only after the algorithm determines that there’s unnecessary (motionless) events, the footage will be disregarded.

When you are setting motion detection for each camera, you have keep in mind few things such as motion area, sensitivity of the motion detection, and pre/post recording settings. Motion area is as important as motion sensitivity, because both determine when the recording starts. When setting up motion area, it is very important to limit motion active area in the video, so you can avoid false motion events and subsequently save more recording storage. You can exclude parts of the picture you deem unnecessary, such a a tree that triggers the camera all the time.

Motion sensitivity is not as straight forward as the motion area. Most of security systems use range of numbers to determine how their motion detection algorithm works (some variation of H264 standard). Usually, 1 represents the lowest sensitivity whereas the highest (usually 5 or 6) represents the greatest sensitivity. The algorithm will track and compare the differences between subsequent frames, if your sensitivity is set to the highest level, the algorithm will trigger the motion detection even if the differences between these frames are low. Some new recorders allow you to set different areas on the picture with different sensitivity levels. For example you can set the entrance area as very sensitive and the rest rest of the picture in low sensitivity.

Pre-record and post-record settings are very important features that will provide a better performance when recording on motion. As the name suggests, pre-record is the amount of seconds the recorder actually records before the motion event. It’s recommended to set the pre-record above 30 seconds. Post-record record is the amount of seconds the recorder records after the motion event has ended. This way, when you are playing back motion recorded event, you will see before the object has triggered the motion and after it has ended.

Another useful feature is to set the security system to record on motion on certain timeframes only. Let’s say, you can set the system to record continuously 8AM-8PM and on motion during the night time. Motion detection works best in small areas and it is ideal for residential or retail environment. But for larger area such as outdoor of parking lot or inside warehouse, it is recommended for one to use 24-hour recording mode. However, when it’s possible the motion detection is way more convenient than recording continuously. If something happened, you know exactly when to playback. Moreover you will have more days covered on the hard drive (depending on the location camera set on motion may get 3-7 hours of motion recording daily).