libmpdemux/aac_hdr.c

   1 /*
   2  * Copyright (C) 2005 Nico Sabbi
   3  *
   4  * This file is part of MPlayer.
   5  *
   6  * MPlayer is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * MPlayer is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with MPlayer; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19  */
  20
  21 #include <stdint.h>
  22 #include "aac_hdr.h"
  23 #include "libavutil/attributes.h"
  24
  25 /// \param srate (out) sample rate
  26 /// \param num (out) number of audio frames in this ADTS frame
  27 /// \return size of the ADTS frame in bytes
  28 /// aac_parse_frames needs a buffer at least 8 bytes long
  29 int aac_parse_frame(uint8_t *buf, int *srate, int *num)
  30 {
  31         int i = 0, sr, fl = 0, id av_unused;
  32         static int srates[] = {96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000, 0, 0, 0};
  33
  34         if((buf[i] != 0xFF) || ((buf[i+1] & 0xF6) != 0xF0))
  35                 return 0;
  36
  37         id = (buf[i+1] >> 3) & 0x01;    //id=1 mpeg2, 0: mpeg4
  38         sr = (buf[i+2] >> 2)  & 0x0F;
  39         if(sr > 11)
  40                 return 0;
  41         *srate = srates[sr];
  42
  43         fl = ((buf[i+3] & 0x03) << 11) | (buf[i+4] << 3) | ((buf[i+5] >> 5) & 0x07);
  44         *num = (buf[i+6] & 0x02) + 1;
  45
  46         return fl;
  47 }