dsps_dct_f32.c File Reference

#include "dsp_common.h"
#include <math.h>
#include "dsps_dct.h"
#include "dsps_fft2r.h"

Include dependency graph for dsps_dct_f32.c:

Go to the source code of this file.

Functions
esp_err_t	dsps_dct_f32_ref (float *data, int N, float *result)
	DCTs.
esp_err_t	dsps_dct_inverce_f32_ref (float *data, int N, float *result)
esp_err_t	dsps_dct_f32 (float *data, int N)
	DCT of radix 2, unscaled.
esp_err_t	dsps_dct_inv_f32 (float *data, int N)
	Inverce DCT of radix 2.

Function Documentation

dsps_dct_f32()

esp_err_t dsps_dct_f32	(	float *	data,
		int	N )

DCT of radix 2, unscaled.

Discrete Cosine Transform type II of radix 2, unscaled Function is FFT based The extension (_ansi) use ANSI C and could be compiled and run on any platform. The extension (_ae32) is optimized for ESP32 chip.

Parameters

[in,out]	data	input/output array with size of N*2. An elements located: Re[0],Re[1], , ... Re[N-1], any data... up to N*2 result of DCT will be stored to this array from 0...N-1. Size of data array must be N*2!!!
[in]	N	Size of DCT transform. Size of data array must be N*2!!!

Returns

• ESP_OK on success
• One of the error codes from DSP library

Definition at line 47 of file dsps_dct_f32.c.

{
    esp_err_t ret = ESP_OK;
    if (dsps_fft2r_initialized == 0) {
        return ESP_ERR_DSP_REINITIALIZED;
    }
 
    for (int i = 0; i < N / 2; i++) {
        data[(N - 1 - i) * 2] = data[i * 2 + 1];
        data[i * 2 + 1] = 0;
        data[N + i * 2 + 1] = 0;
    }
 
    ret = dsps_fft2r_fc32(data, N);
    if (ret != ESP_OK) {
        return ret;
    }
 
    // // The follows code do the same as this one:
    // //
    // float factor = M_PI / (N * 2);
    // ret = dsps_bit_rev_fc32(data, N);
    // for (int i = 0; i < N; i++) {
    //  float temp = i * factor;
    //  data[i] = data[i*2] * cosf(temp) + data[i*2 + 1] * sinf(temp);
    // }
    int table_step = 2;
    for (int i = 0; i < N; i++) {
        float c =  dsps_fft_w_table_fc32[i * 2 * table_step];
        float s =  dsps_fft_w_table_fc32[i * 2 * table_step + 1];
        data[i * 2] = data[i * 2] * c;
        data[i * 2 + 1] = data[i * 2 + 1] * s;
    }
    ret = dsps_bit_rev_fc32(data, N);
    if (ret != ESP_OK) {
        return ret;
    }
 
    for (int i = 0; i < N; i++) {
        data[i] = data[i * 2] + data[i * 2 + 1];
    }
    return ESP_OK;
}

References data, dsps_bit_rev_fc32, dsps_fft2r_fc32, dsps_fft2r_initialized, dsps_fft_w_table_fc32, ESP_ERR_DSP_REINITIALIZED, ESP_OK, and N.

dsps_dct_f32_ref()

esp_err_t dsps_dct_f32_ref	(	float *	data,
		int	N,
		float *	result )

DCTs.

Direct DCT type II and Inverce DCT type III, unscaled These functions used as a reference for general purpose. These functions are not optimyzed! The extension (_ansi) use ANSI C and could be compiled and run on any platform. The extension (_ae32) is optimized for ESP32 chip.

Parameters

[in]	data	input/output array with size of N. An elements located: Re[0],Re[1], , ... Re[N-1]
[in]	N	Size of DCT transform. Size of data array must be N*2!!!
[out]	result	output result array with size of N.

Returns

• ESP_OK on success
• One of the error codes from DSP library

Definition at line 21 of file dsps_dct_f32.c.

{
    float factor = M_PI / N;
    for (size_t i = 0; i < N; i++) {
        float sum = 0;
        for (size_t j = 0; j < N; j++) {
            sum += data[j] * cosf((j + 0.5) * i * factor);
        }
        result[i] = sum;
    }
    return ESP_OK;
}

References data, ESP_OK, M_PI, and N.

dsps_dct_inv_f32()

esp_err_t dsps_dct_inv_f32	(	float *	data,
		int	N )

Inverce DCT of radix 2.

Inverce Discrete Cosine Transform type II of radix 2, unscaled Function is FFT based The extension (_ansi) use ANSI C and could be compiled and run on any platform. The extension (_ae32) is optimized for ESP32 chip.

Parameters

[in,out]	data	input/output array with size of N*2. An elements located: Re[0],Re[1], , ... Re[N-1], any data... up to N*2 result of DCT will be stored to this array from 0...N-1. Size of data array must be N*2!!!
[in]	N	Size of DCT transform. Size of data array must be N*2!!!

Returns

• ESP_OK on success
• One of the error codes from DSP library

Definition at line 91 of file dsps_dct_f32.c.

{
    esp_err_t ret = ESP_OK;
    if (dsps_fft2r_initialized == 0) {
        return ESP_ERR_DSP_REINITIALIZED;
    }
 
    float factor = M_PI / (N * 2);
    data[0] *= 0.5;
    for (int i = N - 1; i >= 0; i--) {
        float temp = i * factor;
        data[i * 2] = data[i] * cosf(temp);
        data[i * 2 + 1] = data[i] * -sinf(temp);
    }
    ret = dsps_fft2r_fc32(data, N);
    if (ret != ESP_OK) {
        return ret;
    }
    ret = dsps_bit_rev_fc32(data, N);
    if (ret != ESP_OK) {
        return ret;
    }
    for (size_t i = 0; i < N / 2; i++) {
        data[i * 2 + 1] = data[(N - 1 - i) * 2];
    }
 
    return ESP_OK;
}

References data, dsps_bit_rev_fc32, dsps_fft2r_fc32, dsps_fft2r_initialized, ESP_ERR_DSP_REINITIALIZED, ESP_OK, M_PI, and N.

dsps_dct_inverce_f32_ref()

esp_err_t dsps_dct_inverce_f32_ref	(	float *	data,
		int	N,
		float *	result )

Definition at line 34 of file dsps_dct_f32.c.

{
    float factor = M_PI / N;
    for (size_t i = 0; i < N; i++) {
        float sum = data[0] / 2;
        for (size_t j = 0; j < N; j++) {
            sum += data[j] * cosf(j * (i + 0.5) * factor);
        }
        result[i] = sum;
    }
    return ESP_OK;
}

References data, ESP_OK, M_PI, and N.