Resolution and bitrate¶
Bitrate is a unit that indicates how much multimedia data, such as video or audio, is processed and transmitted per second.
It is a key factor that determines the image quality and file size of a video.
As the amount of data transmitted per second, it is related to communication bandwidth and file size.
| Name | Resolution | Average bitrate |
|---|---|---|
| CIF | 352x240 | 100kbps |
| D1(4CIF) | 704x480 | 400kbps |
| 1MP(720P) | 1280x720 | 910kbps |
| FHD(2MP, 1080P) | 1920x1080 | 2048kbps |
| QHD(1440p) | 2560x1440 | 3600kbps |
| 4M | 2688x1520 | 4000kbps |
| 5M | 2592x1944 | 5000kbps |
| 6M | 3072x2048 | 6200kbps |
| 4K(8M,UHD) | 3840x2160 | 8200kbps |
| 10M | 3648x2752 | 9900kbps |
| 12M | 4000x3000 | 11900kbps |
These are average bitrates based on H.264.
H.265 offers about 25%–50% better compression efficiency compared to H.264.
For example, 2048kbps quality in H.264 and 1024kbps in H.265 show similar image quality.
For video storage, the storage capacity varies according to the bitrate, so there is no difference whether you store in H.264 or H.265.
Depending on how the bitrate is set, it is largely divided into two types. It can be set in a CCTV system or during video encoding.
1. Constant Bitrate (CBR)¶
- Characteristic: Keeps the bitrate constant regardless of the video content (scene complexity or motion).
- Advantage: Network bandwidth and file size can be predicted accurately, which is stable for streaming.
- Disadvantage: Image quality may degrade in scenes with a lot of motion and complexity.
2. Variable Bitrate (VBR)¶
- Characteristic: Changes the bitrate according to the video content. It lowers the bitrate in static scenes and raises it in scenes with a lot of motion and complexity to secure image quality.
- Advantage: At the same average file size, it can achieve better image quality than CBR.
- Disadvantage: During real-time streaming, the required bandwidth can spike momentarily, which may cause network delays.