Delta QP - Delta QP - 3.0 English - PG447

Encoder rate control assigns a QP based on the rate control algorithm type and target rate. An extra delta QP can be specified, based on a picture’s temporal-ID, to be added on top of the rate control generated QPs. This allows for increasing or decreasing the picture quality based on the temporal layer IDs. Going higher up the layers, it is better to have a higher average QP to maintain better subjective quality. Example: If layer 0's QP value is "X", and layer 1's is "X + 2", and layer 2's is "X+4," then the delta QPs should be set as 2 and 4 accordingly for layer 1 and layer 2.

RateCtrlMode=CONST_QP is not supported for delta QP.

Enable delta QP option the configuration file.

Gop.TempDQP = 1 1 1 1

Similarly, to have different base frame QPs depending on the temporal layer, a Lambda table for different layers can be specified. This improves the subjective quality depending on video content. To enable a temporal ID, enable the LambdaFactors parameter in the configuration file and copy Lambdas.hex file in the working directory. Refer to Lambda File Format.

LambdaFactors = 0.20 0.35 0.59 0.60 0.61 0.62