## SPpcXec

#### Routine

void SPpcXec (const float pc[], float ec[], int Np)

#### Purpose

Convert predictor coefficients to prediction error filter coefficients

#### Description

The error filter coefficients are related to the predictor filter coefficients by,

      ec[0]  = 1
      ec[1]  = -pc[0]
            ...
      ec[Np] = -pc[Np-1]

Predictor coefficients are usually expressed algebraically as vectors with 1-offset indexing. The correspondence to the 0-offset C-arrays is as follows.

      p(1) <==> pc[0]       predictor coefficient corresponding to lag 1
      p(i) <==> pc[i-1]     1 <= i < Np

#### Parameters

-> const float pc[]
  Vector of predictor coefficients (Np values). These are the coefficients of the predictor filter, with pc[0] being the predictor coefficient corresponding to lag 1, and pc[Np-1] corresponding to lag Np.
<- float ec[]
  Prediction error (residual) filter coefficients (Np + 1 values)
-> int Np
  Number of predictor coefficients (Np can be zero)

#### Author / revision

P. Kabal / Revision 1.9 2003/05/09

Main Index libtsp