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/*
*
* utils for AAC informations
*/
#include <glib.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define ADTS_HEADER_SIZE 8
#define SEEK_TABLE_CHUNK 60
#define MPEG4_TYPE 0
#define MPEG2_TYPE 1
// Read ADTS header, the file descriptor must be at
// the begining of the aac frame not at the id3tag
int getAacInfo(FILE *fd)
{
unsigned char header[ADTS_HEADER_SIZE];
unsigned int id;
unsigned long originPosition;
originPosition = ftell(fd);
if(fread(header, 1, ADTS_HEADER_SIZE, fd) != ADTS_HEADER_SIZE){
fseek(fd, originPosition, SEEK_SET);
return(-1);
}
if(!((header[0]==0xFF)&&((header[1]& 0xF6)==0xF0))){
printf("Bad header\n");
return(-1);
}
id = header[1]&0x08;
if(id==0){//MPEG-4 AAC
fseek(fd, originPosition, SEEK_SET);
return(MPEG4_TYPE);
}else{
fseek(fd, originPosition, SEEK_SET);
return(MPEG2_TYPE);
}
fseek(fd, originPosition, SEEK_SET);
return(-1);
}
// as AAC is VBR we need to check all ADTS header
// to enable seeking...
// there is no other solution
void checkADTSForSeeking(FILE *fd,
unsigned long **seekTable,
unsigned long *seekTableLength)
{
unsigned long originPosition;
unsigned long position;
unsigned char header[ADTS_HEADER_SIZE];
unsigned int frameCount, frameLength, frameInsec;
unsigned int id=0, seconds=0;
originPosition = ftell(fd);
for(frameCount=0,frameInsec=0;; frameCount++,frameInsec++){
position = ftell(fd);
if(fread(header, 1, ADTS_HEADER_SIZE, fd)!=ADTS_HEADER_SIZE){
break;
}
if(!strncmp(header, "ID3", 3)){
break;
}
if(!((header[0]==0xFF)&&((header[1]& 0xF6)==0xF0))){
printf("error : Bad 1st header, file may be corrupt !\n");
break;
}
if(!frameCount){
id=header[1]&0x08;
if(((*seekTable) = malloc(SEEK_TABLE_CHUNK * sizeof(unsigned long)))==0){
printf("malloc error\n");
return;
}
(*seekTableLength) = SEEK_TABLE_CHUNK;
}
//if(id==0){//MPEG-4
//frameLength = ((unsigned int)header[4]<<5)|((unsigned int)header[5]>>3);
//}else{//MPEG-2
frameLength = (((unsigned int)header[3]&0x3)<<11)|((unsigned int)header[4]<<3)|(header[5]>>5);
//}
if(frameInsec==43){//???
frameInsec=0;
}
if(frameInsec==0){
if(seconds == (*seekTableLength)){
(*seekTable) = realloc((*seekTable), (seconds+SEEK_TABLE_CHUNK)*sizeof(unsigned long));
(*seekTableLength) = seconds+SEEK_TABLE_CHUNK;
}
(*seekTable)[seconds] = position;
seconds++;
}
if(fseek(fd, frameLength-ADTS_HEADER_SIZE, SEEK_CUR)==-1){
break;
}
}
(*seekTableLength) = seconds;
fseek(fd, originPosition, SEEK_SET);
}
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