转:
1、PCM格式介绍:
PCM(Pulse Code Modulation)也被称为 脉码编码调制。PCM中的声音数据没有被压缩,如果是单声道的文件,采样数据按时间的先后顺序依次存入。(它的基本组织单位是BYTE(8bit)或WORD(16bit))
参考文献http://blog.csdn.net/ownwell/article/details/8114121/
2、WAV格式
(1)格式介绍:
WAVE文件格式是Microsoft的RIFF规范的一个子集,用于存储多媒体文件。WAVE文件通常只是一个具有单个“WAVE”块的RIFF文件,该块由两个子块(”fmt”子数据块和”data”子数据块)组成。
如下图所示:
(2)每个字段的的含义介绍:
typedef struct{
char ChunkID[4];//内容为"RIFF"
unsigned long ChunkSize;//存储文件的字节数(不包含ChunkID和ChunkSize这8个字节)
char Format[4];//内容为"WAVE"
}WAVE_HEADER;
typedef struct{
char Subchunk1ID[4];//内容为"fmt"
unsigned long Subchunk1Size;//存储该子块的字节数(不含前面的Subchunk1ID和Subchunk1Size这8个字节)
unsigned short AudioFormat;//存储音频文件的编码格式,例如若为PCM则其存储值为1,若为其他非PCM格式的则有一定的压缩。
unsigned short NumChannels;//通道数,单通道(Mono)值为1,双通道(Stereo)值为2,等等
unsigned long SampleRate;//采样率,如8k,44.1k等
unsigned long ByteRate;//每秒存储的bit数,其值=SampleRate * NumChannels * BitsPerSample/8
unsigned short BlockAlign;//块对齐大小,其值=NumChannels * BitsPerSample/8
unsigned short BitsPerSample;//每个采样点的bit数,一般为8,16,32等。
}WAVE_FMT;
typedef struct{
char Subchunk2ID[4];//内容为“data”
unsigned long Subchunk2Size;//内容为接下来的正式的数据部分的字节数,其值=NumSamples * NumChannels * BitsPerSample/8
}WAVE_DATA;
(3)一个WAVE例子
这里是一个WAVE文件的开头72字节,字节显示为十六进制数字:
52 49 46 46 24 08 00 00 57 41 56 45 66 6d 74 20 10 00 00 00 01 00 02 00
22 56 00 00 88 58 01 00 04 00 10 00 64 61 74 61 00 08 00 00 00 00 00 00
24 17 1e f3 3c 13 3c 14 16 f9 18 f9 34 e7 23 a6 3c f2 24 f2 11 ce 1a 0d
字段解析:
参考文献1http://soundfile.sapp.org/doc/WaveFormat/
参考文献2http://www.lightlink.com/tjweber/StripWav/Canon.html
参考文献3http://www.topherlee.com/software/pcm-tut-wavformat.html
3、用C语言实现PCM转WAVE
#include <stdio.h>
#include <string.h>
/**
* Convert PCM16LE raw data to WAVE format
* @param pcmpath Input PCM file.
* @param channels Channel number of PCM file.
* @param sample_rate Sample rate of PCM file.
* @param wavepath Output WAVE file.
*/
int simplest_pcm16le_to_wave(const char *pcmpath, int channels, int sample_rate, const char *wavepath)
{
typedef struct WAVE_HEADER{
char fccID[4]; //内容为""RIFF
unsigned long dwSize; //最后填写,WAVE格式音频的大小
char fccType[4]; //内容为"WAVE"
}WAVE_HEADER;
typedef struct WAVE_FMT{
char fccID[4]; //内容为"fmt "
unsigned long dwSize; //内容为WAVE_FMT占的字节数,为16
unsigned short wFormatTag; //如果为PCM,改值为 1
unsigned short wChannels; //通道数,单通道=1,双通道=2
unsigned long dwSamplesPerSec;//采用频率
unsigned long dwAvgBytesPerSec;/* ==dwSamplesPerSec*wChannels*uiBitsPerSample/8 */
unsigned short wBlockAlign;//==wChannels*uiBitsPerSample/8
unsigned short uiBitsPerSample;//每个采样点的bit数,8bits=8, 16bits=16
}WAVE_FMT;
typedef struct WAVE_DATA{
char fccID[4]; //内容为"data"
unsigned long dwSize; //==NumSamples*wChannels*uiBitsPerSample/8
}WAVE_DATA;
if(channels==2 || sample_rate==0)
{
channels = 2;
sample_rate = 44100;
}
int bits = 16;
WAVE_HEADER pcmHEADER;
WAVE_FMT pcmFMT;
WAVE_DATA pcmDATA;
unsigned short m_pcmData;
FILE *fp, *fpout;
fp = fopen(pcmpath, "rb+");
if(fp==NULL)
{
printf("Open pcm file error.\n");
return -1;
}
fpout = fopen(wavepath, "wb+");
if(fpout==NULL)
{
printf("Create wav file error.\n");
return -1;
}
/* WAVE_HEADER */
memcpy(pcmHEADER.fccID, "RIFF", strlen("RIFF"));
memcpy(pcmHEADER.fccType, "WAVE", strlen("WAVE"));
fseek(fpout, sizeof(WAVE_HEADER), 1); //1=SEEK_CUR
/* WAVE_FMT */
memcpy(pcmFMT.fccID, "fmt ", strlen("fmt "));
pcmFMT.dwSize = 16;
pcmFMT.wFormatTag = 1;
pcmFMT.wChannels = 2;
pcmFMT.dwSamplesPerSec = sample_rate;
pcmFMT.uiBitsPerSample = bits;
/* ==dwSamplesPerSec*wChannels*uiBitsPerSample/8 */
**pcmFMT.dwAvgBytesPerSec = pcmFMT.dwSamplesPerSec*pcmFMT.wChannels*pcmFMT.uiBitsPerSample/8;**
/* ==wChannels*uiBitsPerSample/8 */
**pcmFMT.wBlockAlign = pcmFMT.wChannels*pcmFMT.uiBitsPerSample/8;**
fwrite(&pcmFMT, sizeof(WAVE_FMT), 1, fpout);
/* WAVE_DATA */
memcpy(pcmDATA.fccID, "data", strlen("data"));
pcmDATA.dwSize = 0;
fseek(fpout, sizeof(WAVE_DATA), SEEK_CUR);
fread(&m_pcmData, sizeof(unsigned short), 1, fp);
while(!feof(fp))
{
pcmDATA.dwSize += 2;
fwrite(&m_pcmData, sizeof(unsigned short), 1, fpout);
fread(&m_pcmData, sizeof(unsigned short), 1, fp);
}
/*pcmHEADER.dwSize = 44 + pcmDATA.dwSize;*/
//修改时间:2018年1月5日
pcmHEADER.dwSize = 36 + pcmDATA.dwSize;
rewind(fpout);
fwrite(&pcmHEADER, sizeof(WAVE_HEADER), 1, fpout);
fseek(fpout, sizeof(WAVE_FMT), SEEK_CUR);
fwrite(&pcmDATA, sizeof(WAVE_DATA), 1, fpout);
fclose(fp);
fclose(fpout);
return 0;
}
int main()
{
simplest_pcm16le_to_wave("NocturneNo2inEflat_44.1k_s16le.pcm", 2, 44100, "output_nocture.wav");
return 0;
}
结果如图所示:
参考文献http://blog.csdn.net/leixiaohua1020/article/details/50534316
2017年10月26日 星期四 修改
原74行代码:
**pcmFMT.dwAvgBytesPerSec = pcmFMT.dwSamplesPerSec*pcmFMT.wChannels*pcmFMT.uiBitsPerSample/8;**
改为
pcmFMT.dwAvgBytesPerSec = pcmFMT.dwSamplesPerSec*pcmFMT.wChannels*pcmFMT.uiBitsPerSample/8;
原76行:
**pcmFMT.wBlockAlign = pcmFMT.wChannels*pcmFMT.uiBitsPerSample/8;**
改为:
pcmFMT.wBlockAlign = pcmFMT.wChannels*pcmFMT.uiBitsPerSample/8;