Function mad_layer_III

modules/data/mp3/libmad/layer3.c:2605–2770

NAME: layer->III() DESCRIPTION: decode a single Layer III frame */

   DESCRIPTION:	decode a single Layer III frame
*/
int mad_layer_III(struct mad_stream *stream, struct mad_frame *frame)
{
  struct mad_header *header = &frame->header;
  unsigned int nch, priv_bitlen, next_md_begin = 0;
  unsigned int si_len, data_bitlen, md_len;
  unsigned int frame_space, frame_used, frame_free;
  struct mad_bitptr ptr;
  struct sideinfo si;
  enum mad_error error;
  int result = 0;
  stack(__FUNCTION__, __FILE__, __LINE__);

  nch = MAD_NCHANNELS(header);
  si_len = (header->flags & MAD_FLAG_LSF_EXT) ?
           (nch == 1 ? 9 : 17) : (nch == 1 ? 17 : 32);

  /* check frame sanity */

  if (stream->next_frame - mad_bit_nextbyte(&stream->ptr) <
      (signed int) si_len) {
    stream->error = MAD_ERROR_BADFRAMELEN;
    stream->md_len = 0;
    return -1;
  }

  /* check CRC word */

  if (header->flags & MAD_FLAG_PROTECTION) {
    header->crc_check =
      mad_bit_crc(stream->ptr, si_len * CHAR_BIT, header->crc_check);

    if (header->crc_check != header->crc_target &&
        !(frame->options & MAD_OPTION_IGNORECRC)) {
      stream->error = MAD_ERROR_BADCRC;
      result = -1;
    }
  }

  /* decode frame side information */

  error = III_sideinfo(&stream->ptr, nch, header->flags & MAD_FLAG_LSF_EXT,
                       &si, &data_bitlen, &priv_bitlen);
  if (error && result == 0) {
    stream->error = error;
    result = -1;
  }

  header->flags        |= priv_bitlen;
  header->private_bits |= si.private_bits;

  /* find main_data of next frame */

  {
    struct mad_bitptr peek;
    unsigned long header;

    mad_bit_init(&peek, stream->next_frame);