| 1 | /* |
| 2 | * Audio and Video frame extraction |
| 3 | * Copyright (c) 2003 Fabrice Bellard |
| 4 | * Copyright (c) 2003 Michael Niedermayer |
| 5 | * Copyright (c) 2009 Alex Converse |
| 6 | * |
| 7 | * This file is part of FFmpeg. |
| 8 | * |
| 9 | * FFmpeg is free software; you can redistribute it and/or |
| 10 | * modify it under the terms of the GNU Lesser General Public |
| 11 | * License as published by the Free Software Foundation; either |
| 12 | * version 2.1 of the License, or (at your option) any later version. |
| 13 | * |
| 14 | * FFmpeg is distributed in the hope that it will be useful, |
| 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 17 | * Lesser General Public License for more details. |
| 18 | * |
| 19 | * You should have received a copy of the GNU Lesser General Public |
| 20 | * License along with FFmpeg; if not, write to the Free Software |
| 21 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 22 | */ |
| 23 | |
| 24 | #include "aac_ac3_parser.h" |
| 25 | #include "aacadtsdec.h" |
| 26 | #include "get_bits.h" |
| 27 | #include "mpeg4audio.h" |
| 28 | |
| 29 | int avpriv_aac_parse_header(GetBitContext *gbc, AACADTSHeaderInfo *hdr) |
| 30 | { |
| 31 | int size, rdb, ch, sr; |
| 32 | int aot, crc_abs; |
| 33 | |
| 34 | if (get_bits(gbc, 12) != 0xfff) |
| 35 | return AAC_AC3_PARSE_ERROR_SYNC; |
| 36 | |
| 37 | skip_bits1(gbc); /* id */ |
| 38 | skip_bits(gbc, 2); /* layer */ |
| 39 | crc_abs = get_bits1(gbc); /* protection_absent */ |
| 40 | aot = get_bits(gbc, 2); /* profile_objecttype */ |
| 41 | sr = get_bits(gbc, 4); /* sample_frequency_index */ |
| 42 | if (!avpriv_mpeg4audio_sample_rates[sr]) |
| 43 | return AAC_AC3_PARSE_ERROR_SAMPLE_RATE; |
| 44 | skip_bits1(gbc); /* private_bit */ |
| 45 | ch = get_bits(gbc, 3); /* channel_configuration */ |
| 46 | |
| 47 | skip_bits1(gbc); /* original/copy */ |
| 48 | skip_bits1(gbc); /* home */ |
| 49 | |
| 50 | /* adts_variable_header */ |
| 51 | skip_bits1(gbc); /* copyright_identification_bit */ |
| 52 | skip_bits1(gbc); /* copyright_identification_start */ |
| 53 | size = get_bits(gbc, 13); /* aac_frame_length */ |
| 54 | if (size < AAC_ADTS_HEADER_SIZE) |
| 55 | return AAC_AC3_PARSE_ERROR_FRAME_SIZE; |
| 56 | |
| 57 | skip_bits(gbc, 11); /* adts_buffer_fullness */ |
| 58 | rdb = get_bits(gbc, 2); /* number_of_raw_data_blocks_in_frame */ |
| 59 | |
| 60 | hdr->object_type = aot + 1; |
| 61 | hdr->chan_config = ch; |
| 62 | hdr->crc_absent = crc_abs; |
| 63 | hdr->num_aac_frames = rdb + 1; |
| 64 | hdr->sampling_index = sr; |
| 65 | hdr->sample_rate = avpriv_mpeg4audio_sample_rates[sr]; |
| 66 | hdr->samples = (rdb + 1) * 1024; |
| 67 | hdr->bit_rate = size * 8 * hdr->sample_rate / hdr->samples; |
| 68 | |
| 69 | return size; |
| 70 | } |