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 #include "portable_io.h"
  17
  18 /**
  19  * Get a new libfaad decoder handle.
  20  *
  21  * \return The handle returned by NeAACDecOpen().
  22  */
  23 NeAACDecHandle aac_open(void)
  24 {
  25         NeAACDecHandle h = NeAACDecOpen();
  26         NeAACDecConfigurationPtr c = NeAACDecGetCurrentConfiguration(h);
  27
  28         c->defObjectType = LC;
  29         c->outputFormat = FAAD_FMT_16BIT;
  30         c->downMatrix = 0;
  31         NeAACDecSetConfiguration(h, c);
  32         return h;
  33 }
  34
  35 static unsigned long aac_read_decoder_length(char *buf, int *description_len)
  36 {
  37         uint8_t b;
  38         uint8_t numBytes = 0;
  39         unsigned long length = 0;
  40
  41         do {
  42                 b = buf[numBytes];
  43                 numBytes++;
  44                 length = (length << 7) | (b & 0x7F);
  45         } while
  46                 ((b & 0x80) && numBytes < 4);
  47         *description_len = numBytes;
  48         return length;
  49 }
  50
  51 /**
  52  * search for the position and the length of the decoder configuration
  53  *
  54  * \param buf buffer to seach
  55  * \param buflen length of \a buf
  56  * \param skip Upon succesful return, this contains the offset in \a buf where
  57  * the decoder config starts.
  58  * \param decoder_length result pointer that is filled in with the length of
  59  * the decoder configuration on success.
  60  *
  61  * \return positive on success, negative on errors
  62  */
  63 int aac_find_esds(char *buf, size_t buflen, size_t *skip,
  64                 unsigned long *decoder_length)
  65 {
  66         size_t i;
  67
  68         for (i = 0; i + 4 < buflen; i++) {
  69                 char *p = buf + i;
  70                 int description_len;
  71
  72                 if (p[0] != 'e' || p[1] != 's' || p[2] != 'd' || p[3] != 's')
  73                         continue;
  74                 i += 8;
  75                 p = buf + i;
  76                 PARA_INFO_LOG("found esds@%zu, next: %x\n", i, (unsigned)*p);
  77                 if (*p == 3)
  78                         i += 8;
  79                 else
  80                         i += 6;
  81                 p = buf + i;
  82                 PARA_INFO_LOG("next: %x\n", (unsigned)*p);
  83                 if (*p != 4)
  84                         continue;
  85                 i += 18;
  86                 p = buf + i;
  87                 PARA_INFO_LOG("next: %x\n", (unsigned)*p);
  88                 if (*p != 5)
  89                         continue;
  90                 i++;
  91                 p = buf + i;
  92                 *decoder_length = aac_read_decoder_length(p, &description_len);
  93                 PARA_INFO_LOG("decoder length: %lu\n", *decoder_length);
  94                 i += description_len;
  95                 *skip = i;
  96                 return 1;
  97         }
  98         return -E_ESDS;
  99 }
 100
 101 /**
 102  * search for the first entry in the stco table
 103  *
 104  * \param buf buffer to seach
 105  * \param buflen length of \a buf
 106  * \param skip Upon succesful return, this contains the number
 107  * of bytes to skip from the input buffer.
 108  *
 109  * \return the position of the first entry in the table on success,
 110  * -E_STCO on errors.
 111  */
 112 ssize_t aac_find_entry_point(char *buf, size_t buflen, size_t *skip)
 113 {
 114         ssize_t ret;
 115         size_t i;
 116
 117         for (i = 0; i + 20 < buflen; i++) {
 118                 char *p = buf + i;
 119
 120                 if (p[0] != 's' || p[1] != 't' || p[2] != 'c' || p[3] != 'o')
 121                         continue;
 122                 PARA_INFO_LOG("found stco@%zu\n", i);
 123                 i += 12;
 124                 ret = read_u32_be(buf + i); /* first offset */
 125                 i += 4;
 126                 PARA_INFO_LOG("entry point: %zd\n", ret);
 127                 *skip = i;
 128                 return ret;
 129         }
 130         PARA_WARNING_LOG("stco not found, buflen: %zu\n", buflen);
 131         return -E_STCO;
 132 }