DCT Type IV Tables

Variables
const float32_t	Weights_128 [256]
	Weights Table. More...
const float32_t	cos_factors_128 [128]
const float32_t	Weights_512 [1024]
const float32_t	cos_factors_512 [512]
const float32_t	Weights_2048 [4096]
const float32_t	cos_factors_2048 [2048]
const float32_t	Weights_8192 [16384]
const float32_t	cos_factors_8192 [8192]
const q31_t	WeightsQ31_128 [256]
const q31_t	cos_factorsQ31_128 [128]
const q31_t	WeightsQ31_512 [1024]
const q31_t	cos_factorsQ31_512 [512]
const q31_t	WeightsQ31_2048 [4096]
const q31_t	cos_factorsQ31_2048 [2048]
const q31_t	WeightsQ31_8192 [16384]
const q31_t	cos_factorsQ31_8192 [8192]

Description

end of RealFFT_Table group

Variable Documentation

const float32_t cos_factors_128[128]

const float32_t cos_factors_2048[2048]

const float32_t cos_factors_512[512]

const float32_t cos_factors_8192[8192]

const q31_t cos_factorsQ31_128[128]

const q31_t cos_factorsQ31_2048[2048]

const q31_t cos_factorsQ31_512[512]

const q31_t cos_factorsQ31_8192[8192]

const float32_t Weights_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)

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)

const float32_t Weights_2048[4096]

const float32_t Weights_512[1024]

const float32_t Weights_8192[16384]

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.

const q31_t WeightsQ31_2048[4096]

const q31_t WeightsQ31_512[1024]

const q31_t WeightsQ31_8192[16384]