前面分享過(guò)一個(gè)算法《音頻增益響度分析 ReplayGain 附完整C代碼示例》

主要用于評(píng)估一定長(zhǎng)度音頻的音量強(qiáng)度，

而分析之后，很多類(lèi)似的需求，肯定是做音頻增益，提高音量諸如此類(lèi)做法。

不過(guò)在項(xiàng)目實(shí)測(cè)的時(shí)候，其實(shí)真的很難定標(biāo)準(zhǔn)，

到底在什么樣的環(huán)境下，要增大音量，還是降低。

在通訊行業(yè)一般的做法就是采用靜音檢測(cè)，

一旦檢測(cè)為靜音或者噪音，則不做處理，反之通過(guò)一定的策略進(jìn)行處理。

這里就涉及到兩個(gè)算法，一個(gè)是靜音檢測(cè)，一個(gè)是音頻增益。

增益其實(shí)沒(méi)什么好說(shuō)的，類(lèi)似于數(shù)據(jù)歸一化拉伸的做法。

靜音檢測(cè)?在WebRTC中?是采用計(jì)算GMM (Gaussian Mixture Model,高斯混合模型)進(jìn)行特征提取的。

在很長(zhǎng)一段時(shí)間里面，音頻特征?有3個(gè)主要的方法，

GMM? ,Spectrogram (聲譜圖), MFCC?即 Mel-Frequency Cepstrum(Mel頻率倒譜)

恕我直言,GMM?提取的特征，其魯棒性 不如后兩者。

也不多做介紹，感興趣的同學(xué)，翻翻 維基百科 ,補(bǔ)補(bǔ)課。

當(dāng)然在實(shí)際使用算法時(shí)，會(huì)由此延伸出來(lái)一些小技巧。

例如，用靜音檢測(cè)?來(lái)做音頻裁剪，或者搭配音頻增益做一些音頻增強(qiáng)之類(lèi)的操作。

自動(dòng)增益在WebRTC?源代碼文件是:analog_agc.c?和?digital_agc.c

靜音檢測(cè)?源代碼文件是: webrtc_vad.c

這個(gè)命名，有一定的歷史原因了。

經(jīng)過(guò)梳理后，

增益算法為 agc.c agc.h

靜音檢測(cè)為 vad.c vad.h

增益算法的完整示例代碼：

#include <stdio.h> #include <stdlib.h> #include <stdint.h> //采用https://github.com/mackron/dr_libs/blob/master/dr_wav.h 解碼 #define DR_WAV_IMPLEMENTATION #include "dr_wav.h" #include "agc.h"#ifndef nullptr #define nullptr 0 #endif#ifndef MIN #define MIN(A, B) ((A) < (B) ? (A) : (B)) #endif//寫(xiě)wav文件 void wavWrite_int16(char *filename, int16_t *buffer, size_t sampleRate, size_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);}} }//讀取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 == nullptr) {printf("讀取wav文件失敗.");}//僅僅處理單通道音頻if (channels != 1) {drwav_free(buffer);buffer = nullptr;*sampleRate = 0;*totalSampleCount = 0;}return buffer; }//分割路徑函數(shù) 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';} }int agcProcess(int16_t *buffer, uint32_t sampleRate, size_t samplesCount, int16_t agcMode) {if (buffer == nullptr) return -1;if (samplesCount == 0) return -1;WebRtcAgcConfig agcConfig;agcConfig.compressionGaindB = 9; // default 9 dBagcConfig.limiterEnable = 1; // default kAgcTrue (on)agcConfig.targetLevelDbfs = 3; // default 3 (-3 dBOv)int minLevel = 0;int maxLevel = 255;size_t samples = MIN(160, sampleRate / 100);if (samples == 0) return -1;const int maxSamples = 320;int16_t *input = buffer;size_t nTotal = (samplesCount / samples);void *agcInst = WebRtcAgc_Create();if (agcInst == NULL) return -1;int status = WebRtcAgc_Init(agcInst, minLevel, maxLevel, agcMode, sampleRate);if (status != 0) {printf("WebRtcAgc_Init fail\n");WebRtcAgc_Free(agcInst);return -1;}status = WebRtcAgc_set_config(agcInst, agcConfig);if (status != 0) {printf("WebRtcAgc_set_config fail\n");WebRtcAgc_Free(agcInst);return -1;}size_t num_bands = 1;int inMicLevel, outMicLevel = -1;int16_t out_buffer[maxSamples];int16_t *out16 = out_buffer;uint8_t saturationWarning = 1; //是否有溢出發(fā)生，增益放大以后的最大值超過(guò)了65536int16_t echo = 0; //增益放大是否考慮回聲影響for (int i = 0; i < nTotal; i++) {inMicLevel = 0;int nAgcRet = WebRtcAgc_Process(agcInst, (const int16_t *const *) &input, num_bands, samples,(int16_t *const *) &out16, inMicLevel, &outMicLevel, echo,&saturationWarning);if (nAgcRet != 0) {printf("failed in WebRtcAgc_Process\n");WebRtcAgc_Free(agcInst);return -1;}memcpy(input, out_buffer, samples * sizeof(int16_t));input += samples;}WebRtcAgc_Free(agcInst);return 1; }void auto_gain(char *in_file, char *out_file) {//音頻采樣率uint32_t sampleRate = 0;//總音頻采樣數(shù)uint64_t inSampleCount = 0;int16_t *inBuffer = wavRead_int16(in_file, &sampleRate, &inSampleCount);//如果加載成功if (inBuffer != nullptr) {// kAgcModeAdaptiveAnalog 模擬音量調(diào)節(jié)// kAgcModeAdaptiveDigital 自適應(yīng)增益// kAgcModeFixedDigital 固定增益 agcProcess(inBuffer, sampleRate, inSampleCount, kAgcModeAdaptiveDigital);wavWrite_int16(out_file, inBuffer, sampleRate, inSampleCount);free(inBuffer);} }int main(int argc, char *argv[]) {printf("WebRTC Automatic Gain Control\n");printf("博客:http://cpuimage.cnblogs.com/\n");printf("音頻自動(dòng)增益\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);auto_gain(in_file, out_file);printf("按任意鍵退出程序 \n");getchar();return 0; }

?

?靜音檢測(cè)完整示例代碼：

#include <stdio.h> #include <stdlib.h> #include <stdint.h> //采用https://github.com/mackron/dr_libs/blob/master/dr_wav.h 解碼 #define DR_WAV_IMPLEMENTATION#include "dr_wav.h" #include "vad.h"#ifndef nullptr #define nullptr 0 #endif#ifndef MIN #define MIN(A, B) ((A) < (B) ? (A) : (B)) #endif#ifndef MAX #define MAX(A, B) ((A) > (B) ? (A) : (B)) #endif//讀取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 == nullptr) {printf("讀取wav文件失敗.");}//僅僅處理單通道音頻if (channels != 1) {drwav_free(buffer);buffer = nullptr;*sampleRate = 0;*totalSampleCount = 0;}return buffer; }int vadProcess(int16_t *buffer, uint32_t sampleRate, size_t samplesCount, int16_t vad_mode, int per_ms_frames) {if (buffer == nullptr) return -1;if (samplesCount == 0) return -1;// kValidRates : 8000, 16000, 32000, 48000// 10, 20 or 30 ms framesper_ms_frames = MAX(MIN(30, per_ms_frames), 10);size_t samples = sampleRate * per_ms_frames / 1000;if (samples == 0) return -1;int16_t *input = buffer;size_t nTotal = (samplesCount / samples);void *vadInst = WebRtcVad_Create();if (vadInst == NULL) return -1;int status = WebRtcVad_Init(vadInst);if (status != 0) {printf("WebRtcVad_Init fail\n");WebRtcVad_Free(vadInst);return -1;}status = WebRtcVad_set_mode(vadInst, vad_mode);if (status != 0) {printf("WebRtcVad_set_mode fail\n");WebRtcVad_Free(vadInst);return -1;}printf("Activity ： \n");for (int i = 0; i < nTotal; i++) {int nVadRet = WebRtcVad_Process(vadInst, sampleRate, input, samples);if (nVadRet == -1) {printf("failed in WebRtcVad_Process\n");WebRtcVad_Free(vadInst);return -1;} else {// output resultprintf(" %d \t", nVadRet);}input += samples;}printf("\n");WebRtcVad_Free(vadInst);return 1; }void vad(char *in_file) {//音頻采樣率uint32_t sampleRate = 0;//總音頻采樣數(shù)uint64_t inSampleCount = 0;int16_t *inBuffer = wavRead_int16(in_file, &sampleRate, &inSampleCount);//如果加載成功if (inBuffer != nullptr) {// Aggressiveness mode (0, 1, 2, or 3)int16_t mode = 1;int per_ms = 30;vadProcess(inBuffer, sampleRate, inSampleCount, mode, per_ms);free(inBuffer);} }int main(int argc, char *argv[]) {printf("WebRTC Voice Activity Detector\n");printf("博客:http://cpuimage.cnblogs.com/\n");printf("靜音檢測(cè)\n");if (argc < 2)return -1;char *in_file = argv[1];vad(in_file);printf("按任意鍵退出程序 \n");getchar();return 0; }

自動(dòng)增益項(xiàng)目地址:https://github.com/cpuimage/WebRTC_AGC

具體流程為：?

加載wav(拖放wav文件到可執(zhí)行文件上)->增益處理->保存為_(kāi)out.wav文件

?

靜音檢測(cè)項(xiàng)目地址：https://github.com/cpuimage/WebRTC_VAD

具體流程為：?

加載wav(拖放wav文件到可執(zhí)行文件上)->輸出靜音檢測(cè)結(jié)果

備注 :1 為非靜音，0 為靜音

?該注意的地方和參數(shù)，見(jiàn)代碼注釋。

用cmake即可進(jìn)行編譯示例代碼，詳情見(jiàn)CMakeLists.txt。

?

若有其他相關(guān)問(wèn)題或者需求也可以郵件聯(lián)系俺探討。

郵箱地址是:?
gaozhihan@vip.qq.com

?

轉(zhuǎn)載于:https://www.cnblogs.com/cpuimage/p/8908551.html

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