简洁明了的插值音频重采样算法例子 (附完整C代码)
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2022-05-10 10:42:23
近一段时间在图像算法以及音频算法之间来回游走。 经常有一些需求,需要将音频进行采样转码处理。 现有的知名开源库,诸如: webrtc , sox等, 代码阅读起来实在闹心。 而音频重采样其实也就是插值算法。 与图像方面的插值算法没有太大的区别。 基于双线性插值的思路。 博主简单实现一个简洁的重采样算 ......
近一段时间在图像算法以及音频算法之间来回游走。
经常有一些需求,需要将音频进行采样转码处理。
现有的知名开源库,诸如: webrtc , sox等,
代码阅读起来实在闹心。
而音频重采样其实也就是插值算法。
与图像方面的插值算法没有太大的区别。
基于双线性插值的思路。
博主简单实现一个简洁的重采样算法,
用在对采样音质要求不高的情况下,也是够用了。
编解码库采用dr_wav
https://github.com/mackron/dr_libs/blob/master/dr_wav.h
近期有点强迫症,纯c实现。
贴上完整代码:
#ifdef __cplusplus extern "C" { #endif #define _CRT_SECURE_NO_WARNINGS #include <stdio.h> #include <stdlib.h> #include <stdint.h> //采用https://github.com/mackron/dr_libs/blob/master/dr_wav.h 解码 #define DR_WAV_IMPLEMENTATION #include "dr_wav.h" void resampler(char *in_file, char *out_file); //写wav文件 void wavWrite_int16(char *filename, int16_t *buffer, int sampleRate, uint32_t totalSampleCount) { drwav_data_format format; format.container = drwav_container_riff; // <-- drwav_container_riff = normal WAV files, drwav_container_w64 = Sony Wave64. format.format = DR_WAVE_FORMAT_PCM; // <-- Any of the DR_WAVE_FORMAT_* codes. format.channels = 1; format.sampleRate = (drwav_uint32) sampleRate; format.bitsPerSample = 16; drwav *pWav = drwav_open_file_write(filename, &format); if (pWav) { drwav_uint64 samplesWritten = drwav_write(pWav, totalSampleCount, buffer); drwav_uninit(pWav); if (samplesWritten != totalSampleCount) { fprintf(stderr, "ERROR\n"); exit(1); } } } //读取wav文件 int16_t *wavRead_int16(char *filename, uint32_t *sampleRate, uint64_t *totalSampleCount) { unsigned int channels; int16_t *buffer = drwav_open_and_read_file_s16(filename, &channels, sampleRate, totalSampleCount); if (buffer == NULL) { printf("读取wav文件失败."); } //仅仅处理单通道音频 if (channels != 1) { drwav_free(buffer); buffer = NULL; *sampleRate = 0; *totalSampleCount = 0; } return buffer; } //分割路径函数 void splitpath(const char *path, char *drv, char *dir, char *name, char *ext) { const char *end; const char *p; const char *s; if (path[0] && path[1] == ':') { if (drv) { *drv++ = *path++; *drv++ = *path++; *drv = '\0'; } } else if (drv) *drv = '\0'; for (end = path; *end && *end != ':';) end++; for (p = end; p > path && *--p != '\\' && *p != '/';) if (*p == '.') { end = p; break; } if (ext) for (s = end; (*ext = *s++);) ext++; for (p = end; p > path;) if (*--p == '\\' || *p == '/') { p++; break; } if (name) { for (s = p; s < end;) *name++ = *s++; *name = '\0'; } if (dir) { for (s = path; s < p;) *dir++ = *s++; *dir = '\0'; } } void resampleData(const int16_t *sourceData, int32_t sampleRate, uint32_t srcSize, int16_t *destinationData, int32_t newSampleRate) { if (sampleRate == newSampleRate) { memcpy(destinationData, sourceData, srcSize * sizeof(int16_t)); return; } uint32_t last_pos = srcSize - 1; uint32_t dstSize = (uint32_t) (srcSize * ((float) newSampleRate / sampleRate)); for (uint32_t idx = 0; idx < dstSize; idx++) { float index = ((float) idx * sampleRate) / (newSampleRate); uint32_t p1 = (uint32_t) index; float coef = index - p1; uint32_t p2 = (p1 == last_pos) ? last_pos : p1 + 1; destinationData[idx] = (int16_t) ((1.0f - coef) * sourceData[p1] + coef * sourceData[p2]); } } void resampler(char *in_file, char *out_file) { //音频采样率 uint32_t sampleRate = 0; //总音频采样数 uint64_t totalSampleCount = 0; int16_t *data_in = wavRead_int16(in_file, &sampleRate, &totalSampleCount); int16_t *data_out = (int16_t *) malloc(totalSampleCount * 2 * sizeof(int16_t)); //如果加载成功 if (data_in != NULL && data_out != NULL) { resampleData(data_in, sampleRate, (uint32_t) totalSampleCount, data_out, sampleRate * 2); wavWrite_int16(out_file, data_out,sampleRate * 2, (uint32_t) totalSampleCount * 2); free(data_in); free(data_out); } else{ if(data_in) free(data_in); if(data_out) free(data_out); } } int main(int argc, char *argv[]) { printf("Audio Processing\n"); printf("博客:http://tntmonks.cnblogs.com/\n"); printf("音频插值重采样\n"); if (argc < 2) return -1; char *in_file = argv[1]; char drive[3]; char dir[256]; char fname[256]; char ext[256]; char out_file[1024]; splitpath(in_file, drive, dir, fname, ext); sprintf(out_file, "%s%s%s_out%s", drive, dir, fname, ext); resampler(in_file, out_file); getchar(); printf("按任意键退出程序 \n"); return 0; } #ifdef __cplusplus } #endif
不多注释,代码比较简单,一看就明了。
示例具体流程为:
加载wav(拖放wav文件到可执行文件上)->重采样为原采样的2倍->保存wav
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