音频demo：使用开源项目lame来将MP3数据解码出PCM数据

1、README

前言

本demo是使用开源项目lame来将MP3数据解码成PCM数据。（环境：x86_64 Ubuntu16.04 64位）

注：在下面【参考文章】中的第1篇里面提到解码出现过异常情况（hip: bitstream problem, resyncing skipping xxx bytes…），或许是因为我屏蔽了main.c中第88行的fseek(…)函数，在目前demo中提供的MP3文件以及网络下载的其他MP3文件解码均未发现此提示。

a. 编译使用

lame的编译：(源码下载地址：https://sourceforge.net/projects/lame/files/lame/)

tar xzf lame-3.100.tar.gz
cd lame-3.100/
./configure --prefix=$PWD/_install --enable-decoder
make
make install

本demo的编译与使用：

$ make clean && make DEBUG=1
$ 
$ ./mp32pcm 
Usage: ./mp32pcm <in MP3 file> <out PCM file>
Examples: ./mp32pcm audio/test1_44100_stereo.mp3 out1_44100_16bit_stereo.pcm./mp32pcm audio/test2_22050_stereo.mp3 out2_22050_16bit_stereo.pcm./mp32pcm audio/test3_22050_mono.mp3   out3_22050_16bit_mono.pcm./mp32pcm audio/test4_8000_mono.mp3    out4_8000_16bit_mono.pcm

b. 参考文章

使用lame解码mp3_Griza_J的博客-CSDN博客_lame 解码
lame mp3解码 - 小小程序员001 - 博客园

c. demo目录架构

$ tree
.
├── audio
│   ├── out1_44100_16bit_stereo.pcm
│   ├── out2_22050_16bit_stereo.pcm
│   ├── out3_22050_16bit_mono.pcm
│   ├── out4_8000_16bit_mono.pcm
│   ├── test1_44100_stereo.mp3
│   ├── test2_22050_stereo.mp3
│   ├── test3_22050_mono.mp3
│   └── test4_8000_mono.mp3
├── docs
│   ├── lame mp3解码 - 小小程序员001 - 博客园.mhtml
│   └── 使用lame解码mp3_Griza_J的博客-CSDN博客_lame 解码.mhtml
├── include
│   └── lame
│       └── lame.h
├── lib
│   └── libmp3lame.a
├── main.c
├── Makefile
└── README.md

2、主要代码片段

main.c

#include <stdio.h>
#include <stdlib.h>#include "lame/lame.h"/* just for debug */
#ifdef ENABLE_DEBUG#define DEBUG(fmt, args...)     printf(fmt, ##args)
#else#define DEBUG(fmt, args...)
#endif#define INBUF_SIZE 		(4096)
#define BUF_SIZE 		(512)
#define MP3BUF_SIZE 	((int)(1.25 * BUF_SIZE) + 7200)int main(int argc, char *argv[])
{char *inMp3FileName = NULL;char *outPcmFileName = NULL;FILE *fpInMP3 = NULL;FILE *fpOutPcm = NULL;short pcm_l[INBUF_SIZE];short pcm_r[INBUF_SIZE];unsigned char mp3Buf[MP3BUF_SIZE];hip_t hip = NULL;if (argc != 3){printf("Usage: \n""    %s <in MP3 file> <out PCM file>\n""Examples: \n""    %s audio/test1_44100_stereo.mp3 out1_44100_16bit_stereo.pcm\n""    %s audio/test2_22050_stereo.mp3 out2_22050_16bit_stereo.pcm\n""    %s audio/test3_22050_mono.mp3   out3_22050_16bit_mono.pcm\n""    %s audio/test4_8000_mono.mp3    out4_8000_16bit_mono.pcm\n",argv[0], argv[0], argv[0], argv[0], argv[0]);return -1;}else{inMp3FileName = argv[1];outPcmFileName = argv[2];}fpInMP3 = fopen(inMp3FileName, "rb");if(!fpInMP3){perror("open input MP3 file failed");goto exit;}fpOutPcm = fopen(outPcmFileName, "wb");if(!fpOutPcm){perror("open output PCM file failed");goto exit;}/* MP3 decode 1/4: init handler */hip = hip_decode_init();if(!hip){printf("init mp3 decoder failed!\n");goto exit;}int readMP3Bytes = -1;int samples = -1;int samplesRate = -1;int channels = -1;mp3data_struct mp3Info = {};/* MP3 decode 2/4: read MP3 header info */do{readMP3Bytes =  fread(mp3Buf, 1, 16, fpInMP3);hip_decode_headers(hip, mp3Buf, readMP3Bytes, pcm_l, pcm_r, &mp3Info);samplesRate = mp3Info.samplerate;channels = mp3Info.stereo;		}while(!mp3Info.header_parsed && readMP3Bytes > 0);// don't need to reset file position//fseek(fpInMP3, 0, SEEK_SET);printf("Input MP3 Info: \n""    samplesRate: %d\n""    channels: %d\n",samplesRate, channels);while(1){readMP3Bytes = fread(mp3Buf, 1, 418, fpInMP3);if(readMP3Bytes <= 0)break;/* MP3 decode 3/4: decode MP3 data */samples = hip_decode(hip, mp3Buf, readMP3Bytes, pcm_l, pcm_r);if(samples > 0){DEBUG("read MP3 bytes: %d \t decode output samples: %d\n", readMP3Bytes, samples);for(int i = 0; i < samples; i++){fwrite(pcm_l + i, 2, 1, fpOutPcm); /* pcm_l/pcm_r type is 'short', so the 'i' don't to multi 2 */if(channels == 2){fwrite(pcm_r + i, 2, 1, fpOutPcm);}}}}printf("\e[32m%s -> %s success\e[0m\n", inMp3FileName, outPcmFileName);exit:/* MP3 decode 4/4: decode exit */if(hip) hip_decode_exit(hip);if(fpOutPcm) {fflush(fpOutPcm);fclose(fpOutPcm);}if(fpInMP3) fclose(fpInMP3);return 0;
}