DCT Type IV Tables

Variables
const float32_t	Weights_128 [256]
	Weights Table.
const q15_t	WeightsQ15_128 [256]
	Weights Table.
const q31_t	WeightsQ31_128 [256]

Description

end of RealFFT_Table group

Variable Documentation

Weights_128

const float32_t Weights_128[256]

Weights Table.

Weights tables are generated using the formula :

weights[n] = e^(-j*n*pi/(2*N))

C command to generate the table

for(i = 0; i< N; i++)
{
  weights[(2*i)]   =  cos (i*c);
  weights[(2*i)+1] = -sin (i*c);
} 

where N is the Number of weights to be calculated and c is pi/(2*N)

In the tables below the real and imaginary values are placed alternatively, hence the array length is 2*N.

cosFactor tables are generated using the formula :

cos_factors[n] = 2 * cos((2n+1)*pi/(4*N))

C command to generate the table

 for(i = 0; i< N; i++)
{
   cos_factors[i]= 2 * cos((2*i+1)*c/2);
} 

where N is the number of factors to generate and c is pi/(2*N)

WeightsQ15_128

const q15_t WeightsQ15_128[256]

Weights Table.

Weights tables are generated using the formula :

weights[n] = e^(-j*n*pi/(2*N))

C command to generate the table

for(i = 0; i< N; i++)
{ 
  weights[(2*i)]   =  cos(i*c);
  weights[(2*i)+1] = -sin(i*c);
} 

where N is the Number of weights to be calculated and c is pi/(2*N)

Converted the output to q15 format by multiplying with 2^31 and saturated if required.

In the tables below the real and imaginary values are placed alternatively, hence the array length is 2*N.

cosFactor tables are generated using the formula :

 cos_factors[n] = 2 * cos((2n+1)*pi/(4*N)) 

C command to generate the table

for (i = 0; i< N; i++)
{
  cos_factors[i] = 2 * cos((2*i+1)*c/2);
} 

where N is the number of factors to generate and c is pi/(2*N)

Then converted to q15 format by multiplying with 2^31 and saturated if required.

WeightsQ31_128

const q31_t WeightsQ31_128[256]

Weights tables are generated using the formula :

weights[n] = e^(-j*n*pi/(2*N))

C command to generate the table

for (i = 0; i< N; i++)
{
  weights[(2*i)]   =  cos(i*c);
  weights[(2*i)+1] = -sin(i*c);
} 

where N is the Number of weights to be calculated and c is pi/(2*N)

Convert the output to q31 format by multiplying with 2^31 and saturated if required.

In the tables below the real and imaginary values are placed alternatively, hence the array length is 2*N.

cosFactor tables are generated using the formula :

cos_factors[n] = 2 * cos((2n+1)*pi/(4*N))

C command to generate the table

for (i = 0; i< N; i++)
{
  cos_factors[i] = 2 * cos((2*i+1)*c/2);
} 

where N is the number of factors to generate and c is pi/(2*N)

Then converted to q31 format by multiplying with 2^31 and saturated if required.