Encoder Bit Rate Control

Three methods are provided to control the bit rate, VBR, CPQ and CBR. You can select the bit rate control method by assigning the BitRateControl element. By default, the value is CPQ.

VBR Method

The VBR —Variable Bit Rate— method delivers an encoded video bit stream at a variable bit rate, depending on the level of motion detected in the scene. This method is a variant of the CPQ method, where you specify a maximum bit rate and an average bit rate, using the MaximumKBitRateControl element and AverageKBitRateControl element.

Typically, the average setting is 50% of the maximum setting. Full frame rate is not anymore possible when setting values above 2,000.

CPQ Method

The CPQ —Constant Picture Quality— method delivers an encoded video bit stream at a constant picture quality level. You can adjust the picture quality level by using the
Quality element.

The maximum bit rate is specified by the application by means of the MaximumKBitRateControl element.

Full frame rate is not anymore possible when setting values above 2,000.

Note. The effective bit rate is continuously varying, in order to maintain a constant subjective image quality.

CBR Method

The CBR —Constant Bit Rate— method delivers an encoded video bit stream at a constant bit rate. You can adjust the targeted bit rate by using the MaximumKBitRateControl element. Full frame rate is not anymore possible when setting values above 2,000.

Note. The effective bit rate is not strictly constant, it may suffer from large short-term variations. However, the long-term average bit rate matches relatively closely the setting.