mp3资料解析代码

2012-06-20
mp3文件解析代码头文件：#include mp3.h// bit率128K bit/sstatic int bitrateTbl[16][BITRATE_NUM] {{
mp3文件解析代码
头文件：
#include "mp3.h"// bit率   128K bit/s  static int bitrateTbl[16][BITRATE_NUM] ={{ -1,  -1},{ 32,   8},{ 40,  16},{ 48,  24},{ 56,  32},{ 64,  40},{ 80,  48},{ 96,  56},{112,  64},{128,  80},{160,  96},{192, 112},{224, 128},{256, 144},{320, 160},{ -1,  -1}};// 采样率static int samplingRateTbl[3][SAMPLERATE_NUM] ={{ 44100, 22050, 11025 },{ 48000, 24000, 12000 },{ 32000, 16000,  8000 }};// 检查帧头信息int checkHdr(uint32_t hdr){if( (hdr & MP3_FRAME_SYNC) != MP3_FRAME_SYNC|| ((hdr>>SHIFT_VERSION) & 0x3) == 1|| ((hdr>>SHIFT_LAYER) & 0x3) == 0|| ((hdr>>SHIFT_BITRATE) & 0xf) == 0xf || ((hdr>>SHIFT_BITRATE) & 0xf) == 0|| ((hdr>>SHIFT_SAMPLERATE)&0x3) == 0x3|| (hdr & 0xffff0000) == 0xfffe0000)return 0;return 1;}#define READ_ERROR(ret) if((ret) < 0) return (ret);int READ_CHAR(FILE * fp, uint32_t * v){char buf[1];if(fread(buf, 1, 1, fp) <= 0)return -1;*v = 0xff & buf[0];return 0;}int READ_UINT16(FILE * fp, uint32_t * v){uint32_t tmp;int ret;ret = READ_CHAR(fp, &tmp);READ_ERROR(ret);*v = (tmp << 8);ret = READ_CHAR(fp, &tmp);READ_ERROR(ret);*v |= (tmp);return 0;}int READ_UINT24(FILE * fp, uint32_t * v){uint32_t tmp;int ret;ret = READ_UINT16(fp, &tmp);READ_ERROR(ret);*v = (tmp << 8);ret = READ_CHAR(fp, &tmp);READ_ERROR(ret);*v |= (tmp);return 0;}int READ_UINT32(FILE * fp, uint32_t * v){uint32_t tmp;int ret;ret = READ_UINT24(fp, &tmp);READ_ERROR(ret);*v = (tmp << 8);ret = READ_CHAR(fp, &tmp);READ_ERROR(ret);*v |= (tmp);return 0;}// 解析mp3帧int getNextFrame(FILE * mp3fp, struct mp3_frame * frame){uint32_t hdr, br_idx, sr_idx;int ret;int factor;do{ret = READ_UINT32(mp3fp, &hdr);//ret = fread(&hdr, 4, 1, mp3fp);if (ret < 0)return -1;if (checkHdr(hdr))break;fseek(mp3fp, -3, 1);}while (1);frame->version = (hdr >> SHIFT_VERSION) & 0x3;br_idx = (hdr >> SHIFT_BITRATE) & 0xf;sr_idx = (hdr >> SHIFT_SAMPLERATE) & 0x3;switch(frame->version){case MPEG_25:frame->bitrate = bitrateTbl[br_idx][BITRATE_MPEG2];frame->samplingRate = samplingRateTbl[sr_idx][SAMPLERATE_MPEG25];factor = 72;break;case MPEG_2:frame->bitrate = bitrateTbl[br_idx][BITRATE_MPEG2];frame->samplingRate = samplingRateTbl[sr_idx][SAMPLERATE_MPEG2];factor = 72;break;case MPEG_1:frame->bitrate = bitrateTbl[br_idx][BITRATE_MPEG1];frame->samplingRate = samplingRateTbl[sr_idx][SAMPLERATE_MPEG1];factor = 144;break;default:printf("invalid header %x\n", hdr);return -1;}frame->size = (factor * frame->bitrate * 1000) / frame->samplingRate;if(frame->size == 0){printf("size == 0\n");return -1;}if((hdr & MASK_PADDING) != 0)frame->size++;if(frame->samplingRate > 32000)frame->samples = 1152;elseframe->samples = 576;frame->channel = hdr & MASK_CHANNEL;fseek(mp3fp, -4, 1);return 0;}
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mp3资料解析代码
