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21st March 2016, 15:02  #1  Link 
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Join Date: Apr 2015
Posts: 7

Rate control for Iframes in HM 16.7
Hi,
I'm trying to understand the rate control algorithm in the HM 16.7 reference software. I have the paper "lambda domain rate control algorithm for High Efficiency Video Coding" by B. Li et al which explains how the Lagrange multiplier lambda for the RDO is found based on a model with 2 parameters (alpha and beta). I can see how this is applied to P and B frames in HM: Code:
estLambda = alpha * pow( bpp, beta ); Code:
(alpha/256.0) * pow( MADPerPixel/bitsPerPixel, beta ) Then, as you can see from the code above, the calculation is based on the "MADPerPixel", where I assume MAD stands for Mean Absolute Difference. However, when calculateLambdaIntra is called in TEncRCPic::estimatePicLambda, MADPerPixel is given as: Code:
pow(m_totalCostIntra/(Double)m_numberOfPixel, 1.2517) Second question: Why is a sum of Hadamard calculated here? What is the link to the calculation of lambda? Any explanation or link to some explaining references would be greatly appreciated! 
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hm encoder, rate control 
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