TSP (libtsp/SP) - SPquant

## SPquant

#### Routine

int SPquant (double x, const float Xq[], int Nreg)

#### Purpose

Binary search for a bounding interval

#### Description

This function returns the index of the quantizer region corresponding to a given input value. The quantizer is specified by an array of quantizer decision levels. A binary search is used to determine the quantizer region.

The index value takes on values from 0 to Nreg-1. If Nreg is equal to one, the index is set to zero. Otherwise, the index is determined as follows, Note that the number of decision levels is one less than the number of regions.

      index            input value
       0                    x <= Xq[0]
       1            Xq[0] < x <= Xq[1]
       2            Xq[1] < x <= Xq[2]
      ...                  ...
       i          Xq[i-1] < x <= Xq[i]
      ...                  ...
     Nreg-2    Xq[Nreg-3] < x <= Xq[Nreg-2]
     Nreg-1    Xq[Nreg-2] < x

#### Parameters

<- int SPquant
  Output index of the quantizer region containing the input value x. SPquant takes on values from 0 to Nreg-1.
-> double x
  Value to be quantized
-> const float Xq[]
  Array of Nreg-1 quantizer decision levels which delimit the Nreg quantizer regions. These levels must be in ascending order.
-> int Nreg
  Number of quantizer regions

#### Author / revision

P. Kabal Copyright (C) 1995 / Revision 1.10 1995/02/09

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