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; }