分享用于学习C++音频处理的代码示例

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 and Encoder:dr_wav

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

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

Format	Bitrate (kbit/s)	1 minute (KiB)	Sample
11,025 Hz 16 bit PCM	176.4	1292	11k16bitpcm.wav
8,000 Hz 16 bit PCM	128	938	8k16bitpcm.wav
11,025 Hz 8 bit PCM	88.2	646	11k8bitpcm.wav
11,025 Hz µ-Law	88.2	646	11kulaw.wav
8,000 Hz 8 bit PCM	64	469	8k8bitpcm.wav
8,000 Hz µ-Law	64	469	8kulaw.wav
11,025 Hz 4 bit ADPCM	44.1	323	11kadpcm.wav
8,000 Hz 4 bit ADPCM	32	234	8kadpcm.wav
11,025 Hz GSM 06.10	18	132	11kgsm.wav
8,000 Hz MP3 16 kbit/s	16	117	8kmp316.wav
8,000 Hz GSM 06.10	13	103	8kgsm.wav
8,000 Hz Lernout & Hauspie SBC 12 kbit/s	12	88	8ksbc12.wav
8,000 Hz DSP Group Truespeech	9	66	8ktruespeech.wav
8,000 Hz MP3 8 kbit/s	8	60	8kmp38.wav
8,000 Hz Lernout & Hauspie CELP	4.8	35	8kcelp.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:

#include <stdio.h>
#include <stdlib.h>    
#include <stdint.h>    
#include <time.h> 
#include <iostream> 
//采用https://github.com/mackron/dr_libs/blob/master/dr_wav.h 解码
#define DR_WAV_IMPLEMENTATION
#include "dr_wav.h"

auto const epoch = clock();
static double now()
{
    return  (clock() - epoch);
};

template <typename FN>
static double bench(const FN &fn)
{
    auto took = -now();
    return (fn(), took + now()) / 1000;
}

//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 = 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);
    } 
}
//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 = '';
        }
    }
    else if (drv)
        *drv = '';
    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 = '';
    }
    if (dir) {
        for (s = path; s < p;)
            *dir++ = *s++;
        *dir = '';
    }
}

int main(int argc, char* argv[])
{
    std::cout << "Audio Processing " << std::endl;
    std::cout << "博客:http://cpuimage.cnblogs.com/" << std::endl;
    std::cout << "支持解析单通道wav格式." << std::endl;

    if (argc < 2) return -1;
    char* in_file = argv[1];

    //音频采样率
    uint32_t sampleRate = 0;
    //总音频采样数
    uint64_t totalSampleCount = 0;
    int16_t* wavBuffer = NULL;
    double nLoadTime = bench([&]
    {
        wavBuffer = wavRead_int16(in_file, &sampleRate, &totalSampleCount);
    });
    std::cout << " 加载耗时: " << int(nLoadTime * 1000) << " 毫秒" << std::endl;

    //如果加载成功
    if (wavBuffer != NULL)
    {
        //将前面一般进行静音处理，直接置零即可
        for (uint64_t i = 0; i < totalSampleCount / 2; i++)
        {
            wavBuffer[i] = 0;
        }
    }
    //保存结果
    double nSaveTime = bench([&]
    {
        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);
        wavWrite_int16(out_file, wavBuffer, sampleRate, totalSampleCount);
    });
    std::cout << " 保存耗时: " << int(nSaveTime * 1000) << " 毫秒" << std::endl;
    if (wavBuffer)
    {
        free(wavBuffer);
    }
    getchar();
    std::cout << "按任意键退出程序 
" << std::endl;
    return 0;
}

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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