void next_start_code()
{
if (seek_sync(START_CODE_PREFIX, 24))
return;
else
exit(1);
}
void next_start_code()
{
if (seek_sync(SYNCWORD, 12))
return;
else
exit(1);
}
void main(int argc, char**argv)
{
FILE *musicout;
Bit_stream_struc bs;
frame_params fr_ps;
III_side_info_t III_side_info;
III_scalefac_t III_scalefac;
unsigned int old_crc;
layer info;
int sync, clip;
int done = FALSE;
unsigned long frameNum=0;
unsigned long bitsPerSlot;
unsigned long sample_frames;
typedef short PCM[2][SSLIMIT][SBLIMIT];
PCM *pcm_sample;
pcm_sample = (PCM *) mem_alloc((long) sizeof(PCM), "PCM Samp");
if (argc==1) {
printf("Useage:decode file.mp3 output.pcm\n");
return;
}
fr_ps.header = &info;
if ((musicout = fopen(argv[2], "w+b")) == NULL) {
printf ("Could not create \"%s\".\n", argv[2]);
exit(1);
}
open_bit_stream_r(&bs, argv[1], BUFFER_SIZE);
sample_frames = 0;
while(!end_bs(&bs)) {
//尝试帧同步
sync = seek_sync(&bs, SYNC_WORD, SYNC_WORD_LENGTH);
if (!sync) {
done = TRUE;
printf("\nFrame cannot be located\n");
out_fifo(*pcm_sample, 3, &fr_ps, done, musicout, &sample_frames);
break;
}
//解码帧头
decode_info(&bs, &fr_ps);
//将fr_ps.header中的信息解读到fr_ps的相关域中
hdr_to_frps(&fr_ps);
//输出相关信息
if(frameNum == 0)
WriteHdr(&fr_ps);
printf("\r%05lu", frameNum++);
if (info.error_protection)
buffer_CRC(&bs, &old_crc);
switch (info.lay) {
case 3:
{
int nSlots, main_data_end, flush_main;
int bytes_to_discard, gr, ch, ss, sb;
static int frame_start = 0;
bitsPerSlot = 8;
//取Side信息
III_get_side_info(&bs, &III_side_info, &fr_ps);
nSlots = main_data_slots(fr_ps);
//读主数据(Audio Data)
for (; nSlots > 0; nSlots--) /* read main data. */
hputbuf((unsigned int) getbits(&bs,8), 8);
main_data_end = hsstell() / 8; /*of privious frame*/
if ( flush_main=(hsstell() % bitsPerSlot) ) {
hgetbits((int)(bitsPerSlot - flush_main));
main_data_end ++;
}
bytes_to_discard = frame_start - main_data_end - III_side_info.main_data_begin ;
if( main_data_end > 4096 ) { frame_start -= 4096;
rewindNbytes( 4096 );
}
frame_start += main_data_slots(fr_ps);
if (bytes_to_discard < 0) {
printf("Not enough main data to decode frame %d. Frame discarded.\n",
frameNum - 1); break;
}
for (; bytes_to_discard > 0; bytes_to_discard--) hgetbits(8);
clip = 0;
for (gr=0;gr<2;gr++) {
double lr[2][SBLIMIT][SSLIMIT],ro[2][SBLIMIT][SSLIMIT];
//主解码
for (ch=0; ch<fr_ps.stereo; ch++) {
long int is[SBLIMIT][SSLIMIT]; /*保存量化数据*/
int part2_start;
part2_start = hsstell();
//获取比例因子
III_get_scale_factors(&III_scalefac,&III_side_info, gr, ch, &fr_ps);
//Huffman解码
III_hufman_decode(is, &III_side_info, ch, gr, part2_start, &fr_ps);
//反量化采样
III_dequantize_sample(is, ro[ch], &III_scalefac, &(III_side_info.ch[ch].gr[gr]), ch, &fr_ps);
}
//立体声处理
III_stereo(ro, lr, &III_scalefac, &(III_side_info.ch[0].gr[gr]), &fr_ps);
for (ch=0; ch<fr_ps.stereo; ch++) {
double re[SBLIMIT][SSLIMIT];
double hybridIn[SBLIMIT][SSLIMIT];/* Hybrid filter input */
double hybridOut[SBLIMIT][SSLIMIT];/* Hybrid filter out */
double polyPhaseIn[SBLIMIT]; /* PolyPhase Input. */
III_reorder(lr[ch], re, &(III_side_info.ch[ch].gr[gr]), &fr_ps);
//抗锯齿处理
III_antialias(re, hybridIn, /* Antialias butterflies. */
&(III_side_info.ch[ch].gr[gr]), &fr_ps);
//IMDCT
for (sb=0; sb<SBLIMIT; sb++) { /* Hybrid synthesis. */
III_hybrid(hybridIn[sb], hybridOut[sb], sb, ch, &(III_side_info.ch[ch].gr[gr]), &fr_ps);
}
for (ss=0;ss<18;ss++) //多相频率倒置
for (sb=0; sb<SBLIMIT; sb++)
if ((ss%2) && (sb%2))
hybridOut[sb][ss] = -hybridOut[sb][ss];
for (ss=0;ss<18;ss++) { //多相合成
for (sb=0; sb<SBLIMIT; sb++)
polyPhaseIn[sb] = hybridOut[sb][ss];
//子带合成
clip += SubBandSynthesis(polyPhaseIn, ch, &((*pcm_sample)[ch][ss][0]));
}
}
//PCM输出
/* Output PCM sample points for one granule(颗粒). */
out_fifo(*pcm_sample, 18, &fr_ps, done, musicout, &sample_frames);
}
if(clip > 0)
printf("\n%d samples clipped.\n", clip);
}
break;
default:
printf("\nOnly layer III supported!\n");
exit(1);
break;
}
}
close_bit_stream_r(&bs);
fclose(musicout);
printf("\nDecoding done.\n");
return;
}
int main(int argc, char**argv)
{
int pid = 0;//fork();
if (pid == 0) {
// exec("sh",argv);
}
int decodepid = fork();
if (decodepid == 0) {
exec("mp3dec", argv);
}
int mp3pid = 0;//fork();
if (mp3pid == 0) {
// exec("decode", argv);
}
setSampleRate(44100);
Bit_stream_struc bs;
struct frame_params fr_ps;
struct III_side_info_t III_side_info;
unsigned int old_crc;
layer info;
unsigned long bitsPerSlot;
/*if (argc==1) {
printf("Useage:decode file.mp3 output.pcm\n");
return;
}*/
fr_ps.header = &info;
open_bit_stream_r(&bs, "in.mp3", BUFFER_SIZE);
int frame_Num = 0;
while(!end_bs(&bs)) {
//³¢ÊÔ֡ͬ²œ
seek_sync(&bs, SYNC_WORD, SYNC_WORD_LENGTH);
decode_info(&bs, &(fr_ps));
//œ«fr_ps.headerÖеÄÐÅÏ¢œâ¶Áµœfr_psµÄÏà¹ØÓòÖÐ
hdr_to_frps(&(fr_ps));
//Êä³öÏà¹ØÐÅÏ¢
frame_Num = frame_Num + 1;
printf(0, "read frame: %d\n", frame_Num);
if (info.error_protection)
buffer_CRC(&bs, &old_crc);
switch (info.lay) {
case 3:
{
int nSlots, main_data_end, flush_main;
int bytes_to_discard;
static int frame_start = 0;
bitsPerSlot = 8;
//È¡SideÐÅÏ¢
III_get_side_info(&bs, &(III_side_info), &(fr_ps));
nSlots = main_data_slots(fr_ps);
//¶ÁÖ÷ÊýŸÝ(Audio Data)
for (; nSlots > 0; nSlots--) /* read main data. */
hputbuf((unsigned int) getbits(&bs,8), 8);
main_data_end = hsstell() / 8; /*of privious frame*/
if ( (flush_main=(hsstell() % bitsPerSlot))==TRUE ) {
hgetbits((int)(bitsPerSlot - flush_main));
main_data_end ++;
}
bytes_to_discard = frame_start - main_data_end - III_side_info.main_data_begin ;
if( main_data_end > 4096 ) { frame_start -= 4096;
rewindNbytes( 4096 );
}
frame_start += main_data_slots(fr_ps);
// printf(0, "discard : %d\n", bytes_to_discard);
if (bytes_to_discard < 0) {
printf(0, "discard: %d %d %d\n", frame_start, main_data_end, III_side_info.main_data_begin);
//printf(0, "Not enough main data to decode frame %d. Frame discarded.\n",frame_Num - 1);
break;
}
for (; bytes_to_discard > 0; bytes_to_discard--) hgetbits(8);
beginDecode(&fr_ps, &III_side_info);
}
break;
default:
// printf("\nOnly layer III supported!\n");
exit();
break;
}
}
close_bit_stream_r(&bs);
printf(0, "\nPlaying done.\n");
kill(pid);
kill(decodepid);
kill(mp3pid);
wait();
wait();
wait();
exit();
}
