adpcm压缩算法 51示例
时间: 2023-08-16 20:10:04 浏览: 52
下面是一段8051单片机上实现ADPCM编码的示例代码:
```c
#include <reg51.h>
#include <stdio.h>
#include <intrins.h>
#define SCLK P1_0
#define RCLK P1_1
#define DATA P1_2
#define ADPCM_STEPS 89
#define ADPCM_STEP_SHIFT 7
// ADPCM编码表
code int8_t ADPCM_StepSizeTable[16] = {1, 3, 5, 7, 9, 11, 13, 15, 16, 16, 16, 16, 16, 16, 16, 16};
code int16_t ADPCM_SampleTable[16] = {-1, -1, -1, -1, 2, 4, 6, 8, 1, 3, 5, 7, 9, 11, 13, 15};
// ADPCM编码函数
int8_t ADPCM_Encode(int16_t sample, int16_t* prev_sample, int8_t* prev_index) {
int8_t code = 0;
int8_t diff = 0;
int8_t step = ADPCM_StepSizeTable[*prev_index];
// 计算预测值和预测误差
int16_t pred_sample = (*prev_sample * 127 + 64) >> 7;
diff = sample - pred_sample;
if (diff >= 0) {
code = 0;
} else {
code = 8;
diff = -diff;
}
// 计算量化步长
int8_t tmp_step = step;
for (int i = 0; i < ADPCM_STEP_SHIFT; i++) {
if (diff >= tmp_step) {
code |= (1 << i);
diff -= tmp_step;
}
tmp_step >>= 1;
}
// 更新前一采样值和量化器状态
if (code & 8) {
pred_sample -= (ADPCM_SampleTable[*prev_index] * step) >> 3;
step = (step * ADPCM_StepSizeTable[*prev_index]) >> 6;
} else {
pred_sample += (ADPCM_SampleTable[*prev_index] * step) >> 3;
step = (step * ADPCM_StepSizeTable[*prev_index]) >> 6;
}
if (step < 1) {
step = 1;
} else if (step > ADPCM_STEPS) {
step = ADPCM_STEPS;
}
*prev_sample = pred_sample;
*prev_index = code & 0x0f;
return code;
}
// 主函数
void main() {
int16_t prev_sample = 0;
int8_t prev_index = 0;
int16_t sample = 0;
int8_t code = 0;
while (1) {
// 读取采样值
sample = read_adc();
// ADPCM编码
code = ADPCM_Encode(sample, &prev_sample, &prev_index);
// 输出编码结果
DATA = code;
RCLK = 1;
_nop_();
RCLK = 0;
}
}
```
该示例代码实现了一个简单的ADPCM编码器,将输入的采样值进行ADPCM压缩,并将压缩后的编码通过并行输出到外部设备。在主函数中,通过不断读取ADC采样值,调用ADPCM_Encode函数进行编码,并将编码结果输出到外部设备中。