1. A video encoding device comprising: a memory that stores a video sequence; and an encoder configured to: select, for one or more video blocks of a first frame, a quantization parameter (QP) using a dynamically adjustable parametric equation that directly maps predicted numbers of non-zero coefficients after quantization (predicted ρ's) to quantization parameters (QP's) to directly determine the QP's from the predicted ρ's without using a lookup table, wherein the dynamically adjustable parametric equation includes one or more adjustable parameters within a function of the quantization parameter; encode the one or more video blocks of the first frame using the one or more selected QP's; determine one or more actual numbers of non-zero coefficients after quantization (actual ρ's) for the one or more video blocks of the first frame that result from one or more selected QP's; determine a new value for at least one of the one or more adjustable parameters such that the dynamically adjustable parametric equation with the new value maps the predicted ρ's to new QP's, and wherein the new QP's result in actual ρ's that better correspond to the predicted ρ's compared to the actual p's that resulted from the one or more selected QP's; select, for one or more video blocks of a second frame, a new quantization parameter using the dynamically adjustable parametric equation and the new value for at least one of the one or more adjustable parameters; and encode the one or more video blocks of the second frame using the new quantization parameter; wherein the parametric equation substantially corresponds to: 
 ρ= nc×e −ƒ(qp) , where e represents Euler's number, ρ defines the predicted ρ's, nc represents a number of coefficients in a unit under consideration and defines a maximum value of the predicted ρ's and ƒ(qp) is a parametric function of the quantization parameter (QP).