c语言实现线性预测编码
时间: 2023-10-16 07:08:28 浏览: 46
线性预测编码是一种将音频信号压缩的方法,其基本原理是通过利用先前采样的音频信号来预测当前采样值,并对预测误差进行编码,从而实现音频信号的压缩。下面是一个简单的用C语言实现线性预测编码的示例代码:
```c
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <math.h>
#define ORDER 4 // 线性预测阶数
int main(int argc, char* argv[]) {
if (argc != 3) {
fprintf(stderr, "Usage: %s input.raw output.lpc\n", argv[0]);
return -1;
}
FILE *fin = fopen(argv[1], "rb");
if (!fin) {
fprintf(stderr, "Failed to open input file: %s\n", argv[1]);
return -1;
}
FILE *fout = fopen(argv[2], "wb");
if (!fout) {
fprintf(stderr, "Failed to open output file: %s\n", argv[2]);
fclose(fin);
return -1;
}
// 读取输入音频信号
int16_t sample, last_sample = 0;
int32_t residue = 0;
while (fread(&sample, sizeof(int16_t), 1, fin) == 1) {
// 计算线性预测系数
double coef[ORDER+1] = {0}; // 系数数组
double r[ORDER+1] = {0}; // 自相关函数数组
double k[ORDER+1] = {0}; // 反射系数数组
double a[ORDER+1] = {0}; // 预测系数数组
double e = 0; // 预测误差
double alpha = 0; // 预测增益因子
for (int i = 0; i < ORDER+1; i++) {
r[i] = 0;
for (int j = 0; j < 160; j++) {
int index = ftell(fin) / 2 - i + j;
fseek(fin, index * 2, SEEK_SET);
if (fread(&sample, sizeof(int16_t), 1, fin) != 1) {
break;
}
r[i] += sample * last_sample / 160.0;
}
}
k[1] = r[1] / r[0];
a[1] = k[1];
e = r[0] * (1 - k[1] * k[1]);
for (int i = 2; i < ORDER+1; i++) {
double sum = 0;
for (int j = 1; j < i; j++) {
sum += k[j] * r[i-j];
}
k[i] = (r[i] - sum) / e;
a[i] = k[i];
for (int j = 1; j < i; j++) {
a[j] = k[i] * a[i-j] + a[j];
}
e *= 1 - k[i] * k[i];
}
alpha = sqrt(e);
// 编码预测误差
residue = sample - last_sample;
int16_t quantized = round(residue / alpha);
fwrite(&quantized, sizeof(int16_t), 1, fout);
// 更新上一个采样值
last_sample = sample;
}
fclose(fout);
fclose(fin);
return 0;
}
```
注意,上述代码中的预测系数计算部分只是一个简单的实现,并不是最优化的实现方式。实际应用中需要根据具体情况进行优化。
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