关于pcm音频头与a-law音频头的互换代码

在一个项目中有一个关于不同音频播放的问题，需要进行转换。今天突然要用到找了好久，觉得该代码蛮有意义的，记录下以免下次想用找不到。

 

/******************************************************************** function:  g.711 decoder and encoder ********************************************************************///hyy add 2010.4.9 begin#include <stdio.h>#include <string.h>#include <sys/stat.h>typedef unsigned short uint16;typedef unsigned int uint32;#pragma pack(push, 1)// pcm文件头typedef struct{uint32 ChunkID;             //00H 4 char "RIFF"标志uint32 ChunkSize;           //04H 4 long int 文件长度 文总长-8uint32 Format;              //08H 4 char "WAVE"标志uint32 SubChunk1ID;         //0CH 4 char "fmt "标志uint32 SubChunk1Size;       //10H 4 0x10000000H(PCM)过渡字节(不定)uint16 AudioFormat;         //14H 2 int 格式类别（0x01H为PCM形式的声音数据) 0x0100Huint16 NumChannels;         //16H 2 int 通道数，单声道为1，双声道为2uint32 SampleRate;          //18H 4 int 采样率（每秒样本数），表示每个通道的播放速度，uint32 ByteRate;            //1CH 4 long int 波形音频数据传送速率，其值Channels×SamplesPerSec×BitsPerSample/8uint16 BlockAlign;          //20H 2 int 数据块的调整数（按字节算的），其值为Channels×BitsPerSample/8uint16 BitsPerSample;       //22H 2 每样本的数据位数，表示每个声道中各个样本的数据位数。如果有多个声道，对每个声道而言，样本大小都一样。uint32 DataTag;           //24H 4 char 数据标记符＂data＂uint32 DataLen;//28H 4 long int 语音数据的长度(文长-44)}PCM_HEAD, *PPCM_HEAD;// a-law文件头typedef struct{uint32 ChunkID;             //00H 4 char "RIFF"标志uint32 ChunkSize;           //04H 4 long int 文件长度 文总长-8uint32 Format;              //08H 4 char "WAVE"标志uint32 SubChunk1ID;         //0CH 4 char "fmt "标志uint32 SubChunk1Size;       //10H 4 0x12000000H(ALAW)uint16 AudioFormat;         //14H 2 int 格式类别 0x0600Huint16 NumChannels;         //16H 2 int 通道数，单声道为1，双声道为2uint32 SampleRate;          //18H 4 int 采样率（每秒样本数），表示每个通道的播放速度，uint32 ByteRate;            //1CH 4 long int 波形音频数据传送速率，其值Channels×SamplesPerSec×BitsPerSample/8uint16 BlockAlign;          //20H 2 int 数据块的调整数（按字节算的），其值为Channels×BitsPerSample/8//uint16 BitsPerSample;       //22H 2 每样本的数据位数，表示每个声道中各个样本的数据位数。如果有多个声道，对每个声道而言，样本大小都一样。uint32 BitsPerSample;       //22H 2 每样本的数据位数，表示每个声道中各个样本的数据位数。如果有多个声道，对每个声道而言，样本大小都一样。uint32 WaveFact;//26H 4 char "fact"标志uint32 Temp1;//2AH 4 0x04000000Huint32 Temp2;//2EH 4 0x00530700Huint32 DataTag;           //32H 4 char 数据标记符＂data＂uint32 DataLen;//36H 4 long int 语音数据的长度(文长-58)}ALAW_HEAD, *PALAW_HEAD;#pragma pack(pop)//hyy add 2010.4.9 end#defineSIGN_BIT(0x80)/* Sign bit for a A-law byte. */#defineQUANT_MASK(0xf)/* Quantization field mask. */#defineNSEGS(8)/* Number of A-law segments. */#defineSEG_SHIFT(4)/* Left shift for segment number. */#defineSEG_MASK(0x70)/* Segment field mask. */#defineBIAS(0x84)/* Bias for linear code. */#define CLIP        8159static const short seg_aend[8] = {0x1F, 0x3F, 0x7F, 0xFF,    0x1FF, 0x3FF, 0x7FF, 0xFFF};static const short seg_uend[8] = {0x3F, 0x7F, 0xFF, 0x1FF,    0x3FF, 0x7FF, 0xFFF, 0x1FFF};/*********** 本程序是采用查表的方式来近似ln的算法 *************///short alaw2linear(unsigned char a_val),ulaw2linear(unsigned char u_val);//char  linear2alaw(short pcm_val),linear2ulaw(short pcm_val);/*************** 检查输入信号在哪个压缩区间 *********************/static short search( shortval, short*table,shortsize){shorti;for (i = 0; i < size; i++){if (val <= *table++)     //找出一个与输入信号最相近的值（大于）{return (i);}}return (size);}/********************* PCM 2 a-law 的压缩 ****************************/char linear2alaw(short  pcm_val)/* 2's complement (16-bit range) */{shortmask;shortseg;unsigned charaval;pcm_val = pcm_val >> 3;if (pcm_val >= 0){mask = 0xD5;/* sign (7th) bit = 1 */}else{mask = 0x55;/* sign bit = 0 */pcm_val = -pcm_val - 1;}/* Convert the scaled magnitude to segment number. */seg = search(pcm_val, (short *)seg_aend, (short)8);/* Combine the sign, segment, and quantization bits. */if (seg >= 8)/* out of range, return maximum value. */{return (unsigned char) (0x7F ^ mask);}else{aval = (unsigned char) seg << SEG_SHIFT;if (seg < 2){aval |= (pcm_val >> 1) & QUANT_MASK;}else{aval |= (pcm_val >> seg) & QUANT_MASK;}return (aval ^ mask);}}/***************** a-law 2 PCM *******************//* * alaw2linear() - Convert an A-law value to 16-bit linear PCM * */short alaw2linear(unsigned chara_val){shortt;shortseg;a_val ^= 0x55;t = (a_val & QUANT_MASK) << 4;seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;switch (seg){case 0:t += 8;break;case 1:t += 0x108;break;default:t += 0x108;t <<= seg - 1;break;}return ((a_val & SIGN_BIT) ? t : -t);}/*********************** pcm 2 u law *************************/char linear2ulaw(short pcm_val)/* 2's complement (16-bit range) */{shortmask;shortseg;unsigned charuval;/* Get the sign and the magnitude of the value. */pcm_val = pcm_val >> 2;if (pcm_val < 0){pcm_val = -pcm_val;mask = 0x7F;}else{mask = 0xFF;}if ( pcm_val > CLIP ){pcm_val = CLIP;/* clip the magnitude */}pcm_val += (BIAS >> 2);/* Convert the scaled magnitude to segment number. */seg = search(pcm_val, (short *)seg_uend, (short)8);/* * Combine the sign, segment, quantization bits; * and complement the code word. */if (seg >= 8)/* out of range, return maximum value. */{return (unsigned char) (0x7F ^ mask);}else{uval = (unsigned char) (seg << 4) | ((pcm_val >> (seg + 1)) & 0xF);return (uval ^ mask);}}/* * ulaw2linear() - Convert a u-law value to 16-bit linear PCM * * First, a biased linear code is derived from the code word. An unbiased * output can then be obtained by subtracting 33 from the biased code. * * Note that this function expects to be passed the complement of the * original code word. This is in keeping with ISDN conventions. */short ulaw2linear(unsigned charu_val){shortt;/* Complement to obtain normal u-law value. */u_val = ~u_val;/* * Extract and bias the quantization bits. Then * shift up by the segment number and subtract out the bias. */t = ((u_val & QUANT_MASK) << 3) + BIAS;t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));}void print_error(){printf("input Error!\n");printf("input argv[1] in filename\n");printf("input argv[2] 0=pcm:wav -> a-lam:wav\n");printf("              1=a-lam -> a-lam:wav\n");printf("              2=a-lam -> pcm:wav\n");printf("              3=pcm -> pcm:wav\n");printf("              4=pcm -> a-lam:wav\n");printf("              5=a-lam:wav -> pcm:wav\n");printf("input argv[3] out filename\n");printf("input argv[4] filehead len\n");}void init_pcm_head(PPCM_HEAD head){head->ChunkID = 0x46464952;//head->ChunkSize = 0xa17fe4;head->Format = 0x45564157;head->SubChunk1ID = 0x20746d66;head->SubChunk1Size = 0x10;head->AudioFormat = 0x1;head->NumChannels = 0x2;head->SampleRate = 0xac44;head->ByteRate = 0x2b110;head->BlockAlign = 0x4;head->BitsPerSample = 0x10;head->DataTag = 0x61746164;//head->DataLen = 0xa17fc0;}void init_alaw_head(PALAW_HEAD head){head->ChunkID = 0x46464952;//head->ChunkSize = 0x50c012;head->Format = 0x45564157;head->SubChunk1ID = 0x20746d66;head->SubChunk1Size = 0x12;//0x10;head->AudioFormat = 0x6;head->NumChannels = 0x1;//0x2;head->SampleRate = 0x3E80;//0x1f40;//0xac44;// 采样率head->ByteRate = 0x3E80;//0x1f40;//0x2b110;// 波形传送速率head->BlockAlign = 0x01;//0x4;// 调整数head->BitsPerSample = 0x08;//0x10;// 量化数head->WaveFact = 0x74636166;head->Temp1 = 0x4;//head->Temp2 = 0x75300;head->DataTag = 0x61746164;//head->DataLen = 0x50bfe0;}int main(int argc, char * argv[]){FILE *fpin= NULL;FILE *fpout = NULL;PCM_HEAD pcm_head;ALAW_HEAD alaw_head;char format[5] = ".wav";char filename[50];char c;short pcm_val;struct stat st;int move_len = 0;if (argc != 5 || ('0' > argv[2][0] || argv[2][0] > '5')){print_error();return -1;}move_len = atol(argv[4]);if ('0' == argv[2][0])// pcm:wav -> a-lam:wav{fpin = fopen(argv[1], "r");if (NULL == fpin){printf("OpenFile Error!\n");return -1;}memset(filename, 0, sizeof (filename));if (NULL != strstr(argv[3], format)){sprintf(filename, "%s", argv[3]);}else{sprintf(filename, "%s%s", argv[3], format);}fpout = fopen(filename, "w+");if (NULL == fpout){fclose(fpin);printf("OpenFile Error!\n");return -1;}if (1 != fread(&pcm_head, sizeof(PCM_HEAD), 1, fpin)){printf("ReadFile Error!\n");goto END;}if (pcm_head.AudioFormat != 0x1){printf("AudioFormat Error!\n");goto END;}memset(&alaw_head, 0, sizeof (ALAW_HEAD));alaw_head.ChunkID = pcm_head.ChunkID;alaw_head.ChunkSize = (pcm_head.ChunkSize - 36) / 2 + 50;alaw_head.Format = pcm_head.Format;alaw_head.SubChunk1ID = pcm_head.SubChunk1ID;alaw_head.SubChunk1Size = pcm_head.SubChunk1Size;//0x00000012;alaw_head.AudioFormat = 0x0006;alaw_head.NumChannels = pcm_head.NumChannels;alaw_head.SampleRate = pcm_head.SampleRate;alaw_head.ByteRate = pcm_head.ByteRate;alaw_head.BlockAlign = pcm_head.BlockAlign;alaw_head.BitsPerSample = pcm_head.BitsPerSample;alaw_head.WaveFact = 0x74636166;// 值要倒过来 "fact"alaw_head.Temp1 = 0x00000004;alaw_head.Temp2 = (pcm_head.ChunkSize - 36) / 2;//0x00075300;alaw_head.DataTag = pcm_head.DataTag;alaw_head.DataLen = (pcm_head.ChunkSize - 36) / 2;fwrite(&alaw_head, sizeof(ALAW_HEAD), 1, fpout);while (1 == fread(&pcm_val, sizeof(short), 1, fpin)){c = linear2alaw(pcm_val);fputc(c, fpout);}}else if ('5' == argv[2][0])// a-lam:wav -> pcm:wav{fpin = fopen(argv[1], "r");if (NULL == fpin){printf("OpenFile Error!\n");return -1;}memset(filename, 0, sizeof (filename));if (NULL != strstr(argv[3], format)){sprintf(filename, "%s", argv[3]);}else{sprintf(filename, "%s%s", argv[3], format);}fpout = fopen(filename, "w+");if (NULL == fpout){fclose(fpin);printf("OpenFile Error!\n");return -1;}if (1 != fread(&alaw_head, sizeof(ALAW_HEAD), 1, fpin)){printf("ReadFile Error!\n");goto END;}if (alaw_head.AudioFormat != 0x6){printf("AudioFormat Error!\n");goto END;}memset(&pcm_head, 0, sizeof (PCM_HEAD));pcm_head.ChunkID = alaw_head.ChunkID;pcm_head.ChunkSize = alaw_head.DataLen * 2 + 36;pcm_head.Format = alaw_head.Format;pcm_head.SubChunk1ID = alaw_head.SubChunk1ID;pcm_head.SubChunk1Size = alaw_head.SubChunk1Size;//0x00000012;pcm_head.AudioFormat = 0x0001;pcm_head.NumChannels = alaw_head.NumChannels;pcm_head.SampleRate = alaw_head.SampleRate;pcm_head.ByteRate = alaw_head.ByteRate;pcm_head.BlockAlign = alaw_head.BlockAlign;pcm_head.BitsPerSample = alaw_head.BitsPerSample;pcm_head.DataTag = alaw_head.DataTag;pcm_head.DataLen = alaw_head.DataLen * 2;fwrite(&pcm_head, sizeof(PCM_HEAD), 1, fpout);while (1 == fread(&c, sizeof(char), 1, fpin)){pcm_val = alaw2linear(c);fwrite(&pcm_val, sizeof(short), 1, fpout);}}else{if (NULL != strstr(argv[1], format)){printf("FileFormat Error!\n");return -1;}if (stat(argv[1], &st) != 0){printf("Read FileSize Error!\n");return -1;}    fpin = fopen(argv[1], "r");if (NULL == fpin){printf("OpenFile Error!\n");return -1;}memset(filename, 0, sizeof (filename));if (NULL != strstr(argv[3], format)){sprintf(filename, "%s", argv[3]);}else{sprintf(filename, "%s%s", argv[3], format);}fpout = fopen(filename, "w+");if (NULL == fpout){fclose(fpin);printf("OpenFile Error!\n");return -1;}if (move_len){fseek(fpin, move_len, SEEK_SET);}if ('1' == argv[2][0])// a-lam -> a-lam:wav{init_alaw_head(&alaw_head);alaw_head.ChunkSize = (st.st_size - move_len) + 50;alaw_head.Temp2 = (st.st_size - move_len);alaw_head.DataLen = (st.st_size - move_len);fwrite(&alaw_head, sizeof(ALAW_HEAD), 1, fpout);while (1 == fread(&c, sizeof(char), 1, fpin)){fputc(c, fpout);}}else if ('2' == argv[2][0])// a-lam -> pcm:wav{init_pcm_head(&pcm_head);    pcm_head.ChunkSize = (st.st_size - move_len) * 2 + 36;    pcm_head.DataLen = (st.st_size - move_len) * 2;    fwrite(&pcm_head, sizeof(PCM_HEAD), 1, fpout);while (1 == fread(&c, sizeof(char), 1, fpin)){pcm_val = alaw2linear(c);fwrite(&pcm_val, sizeof(short), 1, fpout);}}else if ('3' == argv[2][0])// pcm -> pcm:wav{init_pcm_head(&pcm_head);    pcm_head.ChunkSize = (st.st_size - move_len) + 36;    pcm_head.DataLen = (st.st_size - move_len);    fwrite(&pcm_head, sizeof(PCM_HEAD), 1, fpout);while (1 == fread(&pcm_val, sizeof(short), 1, fpin)){fwrite(&pcm_val, sizeof(short), 1, fpout);}}else if ('4' == argv[2][0])// pcm -> a-lam:wav{init_alaw_head(&alaw_head);alaw_head.ChunkSize = (st.st_size - move_len) / 2 + 50;alaw_head.Temp2 = (st.st_size - move_len) / 2;alaw_head.DataLen = (st.st_size - move_len) / 2;fwrite(&alaw_head, sizeof(ALAW_HEAD), 1, fpout);while (1 == fread(&pcm_val, sizeof(short), 1, fpin)){c = linear2alaw(pcm_val);fputc(c, fpout);}}}printf("OK!\n");END:fclose(fpin);fclose(fpout);return 1;}

注：不同的音频其音频头是有区别的，并且编码方式也不一样。

希望可以给大家提供更多的信息。如果转载请注明出处。