分享用于学习C++音频处理的代码示例

2018-01-13 by 落羽の殇

与《分享用于学习C++图像处理的代码示例》为姊妹篇。

为了便于学习C++音频处理并研究音频算法,

俺写了一个适合初学者学习的小小框架。

麻雀虽小五脏俱全,仅仅考虑单通道处理。

采用Decoder:dr_wav

https://github.com/mackron/dr_libs/blob/master/dr_wav.h

采用Encoder:原本计划采用dr_wav的Encode,但是dr_wav保存的文件头忘记修正音频数据的大小,

采用博主自己实现的代码,仅供学习之用。 

dr_wav用于解析wav文件格式.

关于wav格式的解析移步至:

http://soundfile.sapp.org/doc/WaveFormat/

个人习惯,采用int16的处理方式,也可以通过简单的修改,改为float类型。

 wav音频样本可以从维基百科上(https://en.wikipedia.org/wiki/WAV)下载。

注:少数wav格式不支持

FormatBitrate (kbit/s)1 minute (KiB)Sample
11,025 Hz 16 bit PCM176.4129211k16bitpcm.wav
8,000 Hz 16 bit PCM1289388k16bitpcm.wav
11,025 Hz 8 bit PCM88.264611k8bitpcm.wav
11,025 Hz µ-Law88.264611kulaw.wav
8,000 Hz 8 bit PCM644698k8bitpcm.wav
8,000 Hz µ-Law644698kulaw.wav
11,025 Hz 4 bit ADPCM44.132311kadpcm.wav
8,000 Hz 4 bit ADPCM322348kadpcm.wav
11,025 Hz GSM 06.101813211kgsm.wav
8,000 Hz MP3 16 kbit/s161178kmp316.wav
8,000 Hz GSM 06.10131038kgsm.wav
8,000 Hz Lernout & Hauspie SBC 12 kbit/s12888ksbc12.wav
8,000 Hz DSP Group Truespeech9668ktruespeech.wav
8,000 Hz MP3 8 kbit/s8608kmp38.wav
8,000 Hz Lernout & Hauspie CELP4.8358kcelp.wav

附带处理耗时计算,示例演示了一个简单的将音频前面一半静音处理,并简单注释了一下部分逻辑。

完整代码:

1 2 #include <stdio.h> 3 #include <stdlib.h> 4 #include <stdint.h> 5 #include <time.h> 6 #include <iostream> 7 //采用https://github.com/mackron/dr_libs/blob/master/dr_wav.h 解码 8 #define DR_WAV_IMPLEMENTATION 9 #include "dr_wav.h" 10 11 auto const epoch = clock(); 12 static double now() 13 { 14 return (clock() - epoch); 15 }; 16 17 template <typename FN> 18 static double bench(const FN &fn) 19 { 20 auto took = -now(); 21 return (fn(), took + now()) / 1000; 22 } 23 24 //写wav文件 25 void wavWrite_int16(char* filename, int16_t* buffer, int sampleRate, uint32_t totalSampleCount) { 26 27 FILE* fp = fopen(filename, "wb"); 28 if (fp == NULL) { 29 printf("文件打开失败./n"); 30 return; 31 } 32 //修正写入的buffer长度 33 totalSampleCount *= sizeof(int16_t); 34 int nbit = 16; 35 int FORMAT_PCM = 1; 36 int nbyte = nbit / 8; 37 char text[4] = { 'R', 'I', 'F', 'F' }; 38 uint32_t long_number = 36 + totalSampleCount; 39 fwrite(text, 1, 4, fp); 40 fwrite(&long_number, 4, 1, fp); 41 text[0] = 'W'; 42 text[1] = 'A'; 43 text[2] = 'V'; 44 text[3] = 'E'; 45 fwrite(text, 1, 4, fp); 46 text[0] = 'f'; 47 text[1] = 'm'; 48 text[2] = 't'; 49 text[3] = ' '; 50 fwrite(text, 1, 4, fp); 51 52 long_number = 16; 53 fwrite(&long_number, 4, 1, fp); 54 int16_t short_number = FORMAT_PCM;//默认音频格式 55 fwrite(&short_number, 2, 1, fp); 56 short_number = 1; // 音频通道数 57 fwrite(&short_number, 2, 1, fp); 58 long_number = sampleRate; // 采样率 59 fwrite(&long_number, 4, 1, fp); 60 long_number = sampleRate * nbyte; // 比特率 61 fwrite(&long_number, 4, 1, fp); 62 short_number = nbyte; // 块对齐 63 fwrite(&short_number, 2, 1, fp); 64 short_number = nbit; // 采样精度 65 fwrite(&short_number, 2, 1, fp); 66 char data[4] = { 'd', 'a', 't', 'a' }; 67 fwrite(data, 1, 4, fp); 68 long_number = totalSampleCount; 69 fwrite(&long_number, 4, 1, fp); 70 fwrite(buffer, totalSampleCount, 1, fp); 71 fclose(fp); 72 } 73 //读取wav文件 74 int16_t* wavRead_int16(char* filename, uint32_t* sampleRate, uint64_t *totalSampleCount) { 75 76 unsigned int channels; 77 int16_t* buffer = drwav_open_and_read_file_s16(filename, &channels, sampleRate, totalSampleCount); 78 if (buffer == NULL) { 79 printf("读取wav文件失败."); 80 } 81 //仅仅处理单通道音频 82 if (channels != 1) 83 { 84 drwav_free(buffer); 85 buffer = NULL; 86 *sampleRate = 0; 87 *totalSampleCount = 0; 88 } 89 return buffer; 90 } 91 92 //分割路径函数 93 void splitpath(const char* path, char* drv, char* dir, char* name, char* ext) 94 { 95 const char* end; 96 const char* p; 97 const char* s; 98 if (path[0] && path[1] == ':') { 99 if (drv) {100 *drv++ = *path++;101 *drv++ = *path++;102 *drv = '/0';103 }104 }105 else if (drv)106 *drv = '/0';107 for (end = path; *end && *end != ':';)108 end++;109 for (p = end; p > path && *--p != '//' && *p != '/';)110 if (*p == '.') {111 end = p;112 break;113 }114 if (ext)115 for (s = end; (*ext = *s++);)116 ext++;117 for (p = end; p > path;)118 if (*--p == '//' || *p == '/') {119 p++;120 break;121 }122 if (name) {123 for (s = p; s < end;)124 *name++ = *s++;125 *name = '/0';126 }127 if (dir) {128 for (s = path; s < p;)129 *dir++ = *s++;130 *dir = '/0';131 }132 }133 134 int main(int argc, char* argv[])135 {136 std::cout << "Audio Processing " << std::endl;137 std::cout << "博客:http://tntmonks.cnblogs.com/" << std::endl;138 std::cout << "支持解析单通道wav格式." << std::endl;139 140 if (argc < 2) return -1;141 char* in_file = argv[1];142 143 //音频采样率144 uint32_t sampleRate = 0;145 //总音频采样数146 uint64_t totalSampleCount = 0;147 int16_t* wavBuffer = NULL;148 double nLoadTime = bench([&]149 {150 wavBuffer = wavRead_int16(in_file, &sampleRate, &totalSampleCount);151 });152 std::cout << " 加载耗时: " << int(nLoadTime * 1000) << " 毫秒" << std::endl;153 154 //如果加载成功155 if (wavBuffer != NULL)156 {157 //将前面一般进行静音处理,直接置零即可158 for (uint64_t i = 0; i < totalSampleCount / 2; i++)159 {160 wavBuffer[i] = 0;161 }162 }163 //保存结果164 double nSaveTime = bench([&]165 {166 char drive[3];167 char dir[256];168 char fname[256];169 char ext[256];170 char out_file[1024];171 splitpath(in_file, drive, dir, fname, ext);172 sprintf(out_file, "%s%s%s_out%s", drive, dir, fname, ext);173 wavWrite_int16(out_file, wavBuffer, sampleRate, totalSampleCount);174 });175 std::cout << " 保存耗时: " << int(nSaveTime * 1000) << " 毫秒" << std::endl;176 177 getchar();178 std::cout << "按任意键退出程序 /n" << std::endl;179 return 0;180 }

示例具体流程为:

加载wav(拖放wav文件到可执行文件上)->简单静音处理->保存wav

并对 加载,保存 这2个环节都进行了耗时计算并输出。

  

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