音频编解码之G711

《音视频应用开发系列文章目录》

G711规定了如何将128kbps的raw pcm信号转为64kbps的g711u/g711a音频信号。本文在前人的基础上封装了G711的编解码算法，有两种实现（基于算法和基于查表），查表的速度更快（源码下载）。

#ifndef _G711_H_
#define _G711_H_/***********************************************************
**  Author:kaychan
**  Data:2019-11-21
**  Mail:1203375695@qq.com
**  Explain:a g711 codec use lookup table and algorithm
***********************************************************/// base on lookup table
int g711a_encode(unsigned char *odata, short *idata, int ilen);
int g711u_encode(unsigned char *odata, short *idata, int ilen);
int g711a_decode(short *odata, unsigned char *idata, int ilen);
int g711u_decode(short *odata, unsigned char *idata, int ilen);// base on algorithm
int g711a_encode2(unsigned char g711_data[], const short amp[], int len);
int g711u_encode2(unsigned char g711_data[], const short amp[], int len);
int g711a_decode2(short amp[], const unsigned char g711a_data[], int g711a_bytes);
int g711u_decode2(short amp[], const unsigned char g711u_data[], int g711u_bytes);#endif

AvG711类封装

基于上述封装G711音频编解码类AvG711

AvG711.h

#ifndef _AV_G711_H_
#define _AV_G711_H_/***********************************************************
**  Author:kaychan
**  Data:2019-11-21
**  Mail:1203375695@qq.com
**  Explain:a g711 codec class
***********************************************************/typedef enum AvG711Fmt_E {AvG711Fmt_Alaw = 0,AvG711Fmt_Ulaw = 1,
}AvG711Fmt;class AvG711 {public:AvG711(AvG711Fmt fmt = AvG711Fmt_Alaw);~AvG711();int encode(unsigned char **odata, unsigned char *idata, int ilen);int encode(const char *g711_file, const char *pcm_file);int decode(unsigned char **odata, unsigned char *idata, int ilen);int decode(const char *pcm_file, const char *g711_file);void free_output_data(unsigned char *odata);private:AvG711Fmt fmt_;
};#endif

AvG711.cpp

#include "AvG711.h"
#include "g711.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>AvG711::AvG711(AvG711Fmt fmt) {fmt_ = fmt;
}AvG711::~AvG711() {}int AvG711::encode(unsigned char **odata, unsigned char *idata, int ilen) {if (ilen > 0) {int olen = ilen / 2;*odata = (unsigned char *)malloc(sizeof(unsigned char) * olen);if (*odata) {if(fmt_ == AvG711Fmt_Alaw) return g711a_encode(*odata, (short *)idata, ilen);else if(fmt_ == AvG711Fmt_Ulaw)return g711u_encode(*odata, (short *)idata, ilen);}}return -1;
}int AvG711::encode(const char *g711_file, const char *pcm_file) {FILE *ifile = fopen(pcm_file, "rb");FILE *ofile = fopen(g711_file, "wb");if (ifile && ofile) {int r = -1;do {unsigned char ibuf[160];r = fread(ibuf, 1, 160, ifile);if (r > 0) {unsigned char *obuf;int olen = encode(&obuf, ibuf, r);fwrite(obuf, 1, olen, ofile);free_output_data(obuf);memset(ibuf, 0, sizeof(ibuf));}} while (r > 0);fclose(ifile);fclose(ofile);return 0;}return -1;
}int AvG711::decode(unsigned char **odata, unsigned char *idata, int ilen) {if (ilen > 0) {int olen = ilen * 2;*odata = (unsigned char *)malloc(sizeof(unsigned char) * olen);if (*odata) {if (fmt_ == AvG711Fmt_Alaw)return g711a_decode((short *)(*odata), idata, ilen);else if (fmt_ == AvG711Fmt_Ulaw)return g711u_decode((short *)(*odata), idata, ilen);}}return -1;
}int AvG711::decode(const char *pcm_file, const char *g711_file) {FILE *ifile = fopen(g711_file, "rb");FILE *ofile = fopen(pcm_file, "wb");if (ifile && ofile) {int r = -1;do {unsigned char ibuf[80];r = fread(ibuf, 1, 80, ifile);if (r > 0) {unsigned char *obuf;int olen = decode(&obuf, ibuf, r);fwrite(obuf, 1, olen, ofile);free_output_data(obuf);memset(ibuf, 0, sizeof(ibuf));}} while (r > 0);fclose(ifile);fclose(ofile);return 0;}return -1;
}void AvG711::free_output_data(unsigned char *odata) {free(odata);
}

调用实例

AvG711 g711a(AvG711Fmt_Alaw);
g711a.encode("g711a.g711", "xxx.pcm"); // pcm->pcma
g711a.decode("xxx.pcm", "g711a.g711"); // pcma->pcmAvG711 g711u(AvG711Fmt_Ulaw);
g711u.encode("g711u.g711", "xxx.pcm"); // pcm->pcmu
g711u.decode("xxx.pcm", "g711u.g711"); // pcmu->pcm

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音频编解码之G711

AvG711类封装

AvG711.h

AvG711.cpp

调用实例

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