The duration of video storage in a security surveillance system determines the required hard drive capacity. What capacity is needed to retain video for 30 days? This article introduces how to calculate surveillance storage usage and available recording duration.
Key Terminology
The following factors determine the recording duration:
Bitrate: The bitrate of the camera refers to the bandwidth of the monitoring video stream. It is divided into the Main Stream and Sub Stream. The Main Stream is used for high-definition (HD) preview and storage, while the Sub Stream is generally used for multi-view preview or remote monitoring. Bitrates vary based on resolution, frame rate, and image quality. By default, a 2MP (Megapixel) H.264 camera has a main stream of 4Mbps, and a 1MP camera has 2Mbps.
HDD Capacity: This refers to the storage space of the hard drive. Common specifications include 500GB, 1TB, 2TB, 4TB, and 6TB (1TB=1024GB, 1GB=1024MB). Generally, surveillance hardware supports capacities exceeding 1TB. It is important to note that the actual usable capacity for video storage is approximately 90% of the total nominal capacity (a capacity coefficient of 0.9).
Channel Count: The number of surveillance cameras requiring recording. For example, if 16 cameras need to be recorded, this counts as 16 channels.
Smart Coding: Also known as H.265+/H.264+, smart coding optimizes and improves upon existing coding standards. It maximizes the compression of the video stream while ensuring video and image quality, thereby extending recording duration and saving hard drive capacity.
Calculation Methods
1. Cameras without Smart Coding (Standard Mode)
- Daily Recording Size = Main Stream (Mbps) ÷ 8 × 3600 (seconds) × 24 (hours) × Channel Count ÷ 1024
- Recording Days = HDD Capacity (GB) × 1024 × Coefficient (0.9) × 8 ÷ 3600 (seconds) ÷ 24 (hours) ÷ Main Stream (Mbps) ÷ Channel Count
Example: For one 2MP camera with a 4Mbps main stream, the video size for one day is: 4 ÷ 8 × 3600 × 24 × 1 = 43,200MB ≈ 42GB
Based on the calculation method above, here is the HDD usage under common network conditions:
| Camera Channels | Bitrate | 1 Day (24h) Capacity | Recording Time on 2TB HDD (Days) |
|---|---|---|---|
| 1 Channel | 2Mbps | 21GB | 87 |
| 1 Channel | 4Mbps | 42GB | 43 |
| 4 Channels | 2Mbps | 84GB | 22 |
| 4 Channels | 4Mbps | 168GB | 11 |
| 8 Channels | 2Mbps | 168GB | 11 |
| 8 Channels | 4Mbps | 336GB | 5.4 |
| 16 Channels | 2Mbps | 336GB | 5.4 |
| 16 Channels | 4Mbps | 672GB | 2.7 |
| N Channels | 2Mbps | 21 × N | 87 ÷ N |
| N Channels | 4Mbps | 42 × N | 43 ÷ N |
Analysis: Based on the calculations above, if there are four 2MP cameras (Main Stream 2Mbps) and the video needs to be retained for 7 days, the required storage capacity is at least 7 × 84GB = 588GB. In this case, it is recommended to purchase a hard drive with a capacity greater than 1TB. Similarly, if there are four 1MP cameras and the video needs to be retained for one month (30 days), the required HDD capacity is 30 × 84GB = 2520GB. It is recommended to purchase a hard drive of 3TB or larger.
2. Cameras with Smart Coding Enabled
When smart coding is enabled, the IPC (IP Camera) can adjust the bitrate in real-time according to the complexity of the environment, effectively extending the storage duration. Field tests indicate that H.265+ with a 2Mbps stream typically consumes between 2GB and 7GB per day.
Taking a typical office scenario as an example, a 2MP camera with H.265+ enabled consumes approximately 5.2GB of storage per day. The total capacity and recording days can be calculated as follows:
| Camera Channels | 1 Day (24h) Capacity | Recording Time on 2TB HDD (Days) |
|---|---|---|
| 1 Channel | 5.2GB | 358 |
| 4 Channels | 20.8GB | 90 |
| 8 Channels | 41.6GB | 45 |
| 16 Channels | 83.2GB | 22 |
| 32 Channels | 166.4GB | 11 |
| N Channels | 5.2 × N | 358 ÷ N |