1/* 2 * MPEG-4 Audio common code 3 * Copyright (c) 2008 Baptiste Coudurier <baptiste.coudurier@free.fr> 4 * 5 * This file is part of FFmpeg. 6 * 7 * FFmpeg is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU Lesser General Public 9 * License as published by the Free Software Foundation; either 10 * version 2.1 of the License, or (at your option) any later version. 11 * 12 * FFmpeg is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * Lesser General Public License for more details. 16 * 17 * You should have received a copy of the GNU Lesser General Public 18 * License along with FFmpeg; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21 22#include "bitstream.h" 23#include "mpeg4audio.h" 24 25const int ff_mpeg4audio_sample_rates[16] = { 26 96000, 88200, 64000, 48000, 44100, 32000, 27 24000, 22050, 16000, 12000, 11025, 8000, 7350 28}; 29 30const uint8_t ff_mpeg4audio_channels[8] = { 31 0, 1, 2, 3, 4, 5, 6, 8 32}; 33 34static inline int get_object_type(GetBitContext *gb) 35{ 36 int object_type = get_bits(gb, 5); 37 if (object_type == 31) 38 object_type = 32 + get_bits(gb, 6); 39 return object_type; 40} 41 42static inline int get_sample_rate(GetBitContext *gb, int *index) 43{ 44 *index = get_bits(gb, 4); 45 return *index == 0x0f ? get_bits(gb, 24) : 46 ff_mpeg4audio_sample_rates[*index]; 47} 48 49int ff_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf, int buf_size) 50{ 51 GetBitContext gb; 52 int specific_config_bitindex; 53 54 init_get_bits(&gb, buf, buf_size*8); 55 c->object_type = get_object_type(&gb); 56 c->sample_rate = get_sample_rate(&gb, &c->sampling_index); 57 c->chan_config = get_bits(&gb, 4); 58 c->sbr = -1; 59 if (c->object_type == 5) { 60 c->ext_object_type = c->object_type; 61 c->sbr = 1; 62 c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index); 63 c->object_type = get_object_type(&gb); 64 } else 65 c->ext_object_type = 0; 66 67 specific_config_bitindex = get_bits_count(&gb); 68 69 if (c->ext_object_type != 5) { 70 int bits_left = buf_size*8 - specific_config_bitindex; 71 for (; bits_left > 15; bits_left--) { 72 if (show_bits(&gb, 11) == 0x2b7) { // sync extension 73 get_bits(&gb, 11); 74 c->ext_object_type = get_object_type(&gb); 75 if (c->ext_object_type == 5 && (c->sbr = get_bits1(&gb)) == 1) 76 c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index); 77 break; 78 } else 79 get_bits1(&gb); // skip 1 bit 80 } 81 } 82 return specific_config_bitindex; 83} 84