c语言对音频分帧加窗fft例子
时间: 2023-09-21 22:03:18 浏览: 57
好的,以下是一个简单的 C 语言代码示例:
```c
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define PI 3.14159265358979323846
void frame_and_fft(double* x, int frame_size) {
const int window_size = frame_size / 2;
const double* window = (double*) malloc(sizeof(double) * window_size);
const int hop_size = frame_size / 4;
const int num_frames = (int) ceil((double) (hop_size + (frame_size - 1)) / hop_size);
// Create Hamming window
for (int i = 0; i < window_size; i++) {
window[i] = 0.54 - 0.46 * cos(2 * PI * i / (window_size - 1));
}
// Allocate memory for frames and FFT results
double** frames = (double**) malloc(sizeof(double*) * num_frames);
for (int i = 0; i < num_frames; i++) {
frames[i] = (double*) malloc(sizeof(double) * frame_size);
}
double** fft_results = (double**) malloc(sizeof(double*) * num_frames);
for (int i = 0; i < num_frames; i++) {
fft_results[i] = (double*) malloc(sizeof(double) * frame_size);
}
// Frame and window the signal
for (int i = 0; i < num_frames; i++) {
const int offset = i * hop_size;
for (int j = 0; j < frame_size; j++) {
const int pos = offset + j;
if (pos < 0 || pos >= frame_size) {
frames[i][j] = 0;
} else {
frames[i][j] = x[pos] * window[j];
}
}
}
// Compute the FFT of each frame
for (int i = 0; i < num_frames; i++) {
for (int j = 0; j < frame_size; j++) {
double sum = 0;
for (int k = 0; k < frame_size; k++) {
const double arg = 2 * PI * j * k / frame_size;
sum += frames[i][k] * cos(arg);
sum -= frames[i][k] * sin(arg);
}
fft_results[i][j] = sum / frame_size;
}
}
// Clean up
for (int i = 0; i < num_frames; i++) {
free(frames[i]);
free(fft_results[i]);
}
free(frames);
free(fft_results);
}
int main() {
// Example signal
const int signal_size = 44100; // 1 second of audio at 44.1 kHz
double* x = (double*) malloc(sizeof(double) * signal_size);
for (int i = 0; i < signal_size; i++) {
x[i] = sin(2 * PI * 440 * i / 44100); // 440 Hz sine wave
}
// Frame and FFT
const int frame_size = 1024;
frame_and_fft(x, frame_size);
// Clean up
free(x);
return 0;
}
```
该代码中实现了一个简单的音频分帧加窗 FFT 的例子。其主要流程为:
1. 分帧:将音频信号划分为多个帧,通常相邻帧之间有重叠。本例中采用 25% 的重叠。
2. 加窗:将每个帧应用一个窗函数,以减少处理后面的信号噪声的影响。本例中采用 Hamming 窗。
3. FFT:对每个帧进行 FFT,得到频域信号。
该代码中的处理过程可能并不是最优的,但可以作为您更深入学习的一个起点。希望对您有所帮助!