aac_common.c

   1 /*
   2  * Copyright (C) 2006 Andre Noll <maan@tuebingen.mpg.de>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6 /*
   7  * based in parts on libfaad, Copyright (C) 2003-2005 M. Bakker,
   8  * Ahead Software AG
   9  */
  10
  11 /** \file aac_common.c Common functions of aac_afh and aadcec. */
  12
  13 #include "para.h"
  14 #include "aac.h"
  15 #include "error.h"
  16
  17 /**
  18  * Get a new libfaad decoder handle.
  19  *
  20  * \return The handle returned by NeAACDecOpen().
  21  */
  22 NeAACDecHandle aac_open(void)
  23 {
  24         NeAACDecHandle h = NeAACDecOpen();
  25         NeAACDecConfigurationPtr c = NeAACDecGetCurrentConfiguration(h);
  26
  27         c->defObjectType = LC;
  28         c->outputFormat = FAAD_FMT_16BIT;
  29         c->downMatrix = 0;
  30         NeAACDecSetConfiguration(h, c);
  31         return h;
  32 }
  33
  34 static unsigned long aac_read_decoder_length(unsigned char *buf, int *description_len)
  35 {
  36         uint8_t b;
  37         uint8_t numBytes = 0;
  38         unsigned long length = 0;
  39
  40         do {
  41                 b = buf[numBytes];
  42                 numBytes++;
  43                 length = (length << 7) | (b & 0x7F);
  44         } while
  45                 ((b & 0x80) && numBytes < 4);
  46         *description_len = numBytes;
  47         return length;
  48 }
  49
  50 /**
  51  * search for the position and the length of the decoder configuration
  52  *
  53  * \param buf buffer to seach
  54  * \param buflen length of \a buf
  55  * \param skip Upon succesful return, this contains the offset in \a buf where
  56  * the decoder config starts.
  57  * \param decoder_length result pointer that is filled in with the length of
  58  * the decoder configuration on success.
  59  *
  60  * \return positive on success, negative on errors
  61  */
  62 int aac_find_esds(unsigned char *buf, size_t buflen, size_t *skip,
  63                 unsigned long *decoder_length)
  64 {
  65         size_t i;
  66
  67         for (i = 0; i + 4 < buflen; i++) {
  68                 unsigned char *p = buf + i;
  69                 int description_len;
  70
  71                 if (p[0] != 'e' || p[1] != 's' || p[2] != 'd' || p[3] != 's')
  72                         continue;
  73                 i += 8;
  74                 p = buf + i;
  75                 PARA_INFO_LOG("found esds@%zu, next: %x\n", i, *p);
  76                 if (*p == 3)
  77                         i += 8;
  78                 else
  79                         i += 6;
  80                 p = buf + i;
  81                 PARA_INFO_LOG("next: %x\n", *p);
  82                 if (*p != 4)
  83                         continue;
  84                 i += 18;
  85                 p = buf + i;
  86                 PARA_INFO_LOG("next: %x\n", *p);
  87                 if (*p != 5)
  88                         continue;
  89                 i++;
  90                 p = buf + i;
  91                 *decoder_length = aac_read_decoder_length(p, &description_len);
  92                 PARA_INFO_LOG("decoder length: %lu\n", *decoder_length);
  93                 i += description_len;
  94                 *skip = i;
  95                 return 1;
  96         }
  97         return -E_ESDS;
  98 }
  99
 100 /**
 101  * search for the first entry in the stco table
 102  *
 103  * \param buf buffer to seach
 104  * \param buflen length of \a buf
 105  * \param skip Upon succesful return, this contains the number
 106  * of bytes to skip from the input buffer.
 107  *
 108  * \return the position of the first entry in the table on success,
 109  * -E_STCO on errors.
 110  */
 111 ssize_t aac_find_entry_point(unsigned char *buf, size_t buflen, size_t *skip)
 112 {
 113         ssize_t ret;
 114         size_t i;
 115
 116         for (i = 0; i + 20 < buflen; i++) {
 117                 unsigned char *p = buf + i;
 118
 119                 if (p[0] != 's' || p[1] != 't' || p[2] != 'c' || p[3] != 'o')
 120                         continue;
 121                 PARA_INFO_LOG("found stco@%zu\n", i);
 122                 i += 12;
 123                 ret = aac_read_int32(buf + i); /* first offset */
 124                 i += 4;
 125                 PARA_INFO_LOG("entry point: %zd\n", ret);
 126                 *skip = i;
 127                 return ret;
 128         }
 129         PARA_WARNING_LOG("stco not found, buflen: %zu\n", buflen);
 130         return -E_STCO;
 131 }