func: int avpriv_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf,
                                   int bit_size, int sync_extension)
  {
      GetBitContext gb;
      int specific_config_bitindex;
      init_get_bits(&gb, buf, bit_size);
      c->object_type = get_object_type(&gb);
      c->sample_rate = get_sample_rate(&gb, &c->sampling_index);
      c->chan_config = get_bits(&gb, 4);
      if (c->chan_config < FF_ARRAY_ELEMS(ff_mpeg4audio_channels))
          c->channels = ff_mpeg4audio_channels[c->chan_config];
      c->sbr = -1;
      c->ps  = -1;
      if (c->object_type == AOT_SBR || (c->object_type == AOT_PS &&
          // check for W6132 Annex YYYY draft MP3onMP4
          !(show_bits(&gb, 3) & 0x03 && !(show_bits(&gb, 9) & 0x3F)))) {
          if (c->object_type == AOT_PS)
              c->ps = 1;
          c->ext_object_type = AOT_SBR;
          c->sbr = 1;
          c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
          c->object_type = get_object_type(&gb);
          if (c->object_type == AOT_ER_BSAC)
              c->ext_chan_config = get_bits(&gb, 4);
      } else {
          c->ext_object_type = AOT_NULL;
          c->ext_sample_rate = 0;
      }
      specific_config_bitindex = get_bits_count(&gb);
      if (c->object_type == AOT_ALS) {
          skip_bits(&gb, 5);
          if (show_bits_long(&gb, 24) != MKBETAG('\0','A','L','S'))
              skip_bits_long(&gb, 24);
          specific_config_bitindex = get_bits_count(&gb);
          if (parse_config_ALS(&gb, c))
              return -1;
      }
      if (c->ext_object_type != AOT_SBR && sync_extension) {
          while (get_bits_left(&gb) > 15) {
              if (show_bits(&gb, 11) == 0x2b7) { // sync extension
                  get_bits(&gb, 11);
                  c->ext_object_type = get_object_type(&gb);
                  if (c->ext_object_type == AOT_SBR && (c->sbr = get_bits1(&gb)) == 1)
                      c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
                  if (get_bits_left(&gb) > 11 && get_bits(&gb, 11) == 0x548)
                      c->ps = get_bits1(&gb);
                  break;
              } else
                  get_bits1(&gb); // skip 1 bit
          }
      }
      //PS requires SBR
      if (!c->sbr)
          c->ps = 0;
      //Limit implicit PS to the HE-AACv2 Profile
      if ((c->ps == -1 && c->object_type != AOT_AAC_LC) || c->channels & ~0x01)
          c->ps = 0;
      return specific_config_bitindex;
  }