The difference between CBR and VBR and its applicable scenarios

Two modes

• CBR (Constant Bit Rate): No matter whether the picture is complex or not, the bit rate is constant at the set value. Bandwidth is wasted when the picture is still, Mosaics may occur due to insufficient bit rate when the screen is in violent motion.
• VBR (Dynamic Bit Rate): Within the set upper limit, the bit rate automatically fluctuates with the complexity of the picture. Save space when stationary, For complex scenes, the bit rate is automatically increased to ensure image quality.

Comparison

How to choose

• The storage budget is tight and the number of days needs to be calculated accurately: CBR, the capacity can be calculated very accurately.
• The picture complexity changes greatly (such as entrances, exits, squares): VBR to avoid blurring at critical moments.
• Remote locations with limited network bandwidth: CBR to prevent burst traffic from filling up the link.
• Multi-channel centralized storage: Can be mixed for use, key channel VBR, common channel CBR.

Practical advice

1. VBR needs to set a upper limit code rate, otherwise extreme scenarios may increase the bandwidth instantly.
2. When using VBR to estimate storage, the average value estimated by "upper limit × 0.6" is closer to reality.
3. When smart encoding (H.265+ / Smart encoding) is enabled, the bit rate control will be taken over by the algorithm, and manual settings may be overridden.
4. During acceptance, the inspection should be played back during the most complex periods (such as morning and evening peak hours), rather than just watching static images at night.