Libav
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00001 /* 00002 * AC-3 parser 00003 * Copyright (c) 2003 Fabrice Bellard 00004 * Copyright (c) 2003 Michael Niedermayer 00005 * 00006 * This file is part of FFmpeg. 00007 * 00008 * FFmpeg is free software; you can redistribute it and/or 00009 * modify it under the terms of the GNU Lesser General Public 00010 * License as published by the Free Software Foundation; either 00011 * version 2.1 of the License, or (at your option) any later version. 00012 * 00013 * FFmpeg is distributed in the hope that it will be useful, 00014 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00015 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00016 * Lesser General Public License for more details. 00017 * 00018 * You should have received a copy of the GNU Lesser General Public 00019 * License along with FFmpeg; if not, write to the Free Software 00020 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00021 */ 00022 00023 #include "parser.h" 00024 #include "ac3_parser.h" 00025 #include "aac_ac3_parser.h" 00026 #include "get_bits.h" 00027 00028 00029 #define AC3_HEADER_SIZE 7 00030 00031 00032 static const uint8_t eac3_blocks[4] = { 00033 1, 2, 3, 6 00034 }; 00035 00036 00037 int ff_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr) 00038 { 00039 int frame_size_code; 00040 00041 memset(hdr, 0, sizeof(*hdr)); 00042 00043 hdr->sync_word = get_bits(gbc, 16); 00044 if(hdr->sync_word != 0x0B77) 00045 return AAC_AC3_PARSE_ERROR_SYNC; 00046 00047 /* read ahead to bsid to distinguish between AC-3 and E-AC-3 */ 00048 hdr->bitstream_id = show_bits_long(gbc, 29) & 0x1F; 00049 if(hdr->bitstream_id > 16) 00050 return AAC_AC3_PARSE_ERROR_BSID; 00051 00052 hdr->num_blocks = 6; 00053 00054 /* set default mix levels */ 00055 hdr->center_mix_level = 1; // -4.5dB 00056 hdr->surround_mix_level = 1; // -6.0dB 00057 00058 if(hdr->bitstream_id <= 10) { 00059 /* Normal AC-3 */ 00060 hdr->crc1 = get_bits(gbc, 16); 00061 hdr->sr_code = get_bits(gbc, 2); 00062 if(hdr->sr_code == 3) 00063 return AAC_AC3_PARSE_ERROR_SAMPLE_RATE; 00064 00065 frame_size_code = get_bits(gbc, 6); 00066 if(frame_size_code > 37) 00067 return AAC_AC3_PARSE_ERROR_FRAME_SIZE; 00068 00069 skip_bits(gbc, 5); // skip bsid, already got it 00070 00071 skip_bits(gbc, 3); // skip bitstream mode 00072 hdr->channel_mode = get_bits(gbc, 3); 00073 00074 if(hdr->channel_mode == AC3_CHMODE_STEREO) { 00075 skip_bits(gbc, 2); // skip dsurmod 00076 } else { 00077 if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO) 00078 hdr->center_mix_level = get_bits(gbc, 2); 00079 if(hdr->channel_mode & 4) 00080 hdr->surround_mix_level = get_bits(gbc, 2); 00081 } 00082 hdr->lfe_on = get_bits1(gbc); 00083 00084 hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8; 00085 hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift; 00086 hdr->bit_rate = (ff_ac3_bitrate_tab[frame_size_code>>1] * 1000) >> hdr->sr_shift; 00087 hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on; 00088 hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2; 00089 hdr->frame_type = EAC3_FRAME_TYPE_AC3_CONVERT; //EAC3_FRAME_TYPE_INDEPENDENT; 00090 hdr->substreamid = 0; 00091 } else { 00092 /* Enhanced AC-3 */ 00093 hdr->crc1 = 0; 00094 hdr->frame_type = get_bits(gbc, 2); 00095 if(hdr->frame_type == EAC3_FRAME_TYPE_RESERVED) 00096 return AAC_AC3_PARSE_ERROR_FRAME_TYPE; 00097 00098 hdr->substreamid = get_bits(gbc, 3); 00099 00100 hdr->frame_size = (get_bits(gbc, 11) + 1) << 1; 00101 if(hdr->frame_size < AC3_HEADER_SIZE) 00102 return AAC_AC3_PARSE_ERROR_FRAME_SIZE; 00103 00104 hdr->sr_code = get_bits(gbc, 2); 00105 if (hdr->sr_code == 3) { 00106 int sr_code2 = get_bits(gbc, 2); 00107 if(sr_code2 == 3) 00108 return AAC_AC3_PARSE_ERROR_SAMPLE_RATE; 00109 hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2; 00110 hdr->sr_shift = 1; 00111 } else { 00112 hdr->num_blocks = eac3_blocks[get_bits(gbc, 2)]; 00113 hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code]; 00114 hdr->sr_shift = 0; 00115 } 00116 00117 hdr->channel_mode = get_bits(gbc, 3); 00118 hdr->lfe_on = get_bits1(gbc); 00119 00120 hdr->bit_rate = (uint32_t)(8.0 * hdr->frame_size * hdr->sample_rate / 00121 (hdr->num_blocks * 256.0)); 00122 hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on; 00123 } 00124 hdr->channel_layout = ff_ac3_channel_layout_tab[hdr->channel_mode]; 00125 if (hdr->lfe_on) 00126 hdr->channel_layout |= CH_LOW_FREQUENCY; 00127 00128 return 0; 00129 } 00130 00131 int ff_ac3_parse_header_full(GetBitContext *gbc, AC3HeaderInfo *hdr){ 00132 int ret, i; 00133 ret = ff_ac3_parse_header(gbc, hdr); 00134 if(!ret){ 00135 if(hdr->bitstream_id>10){ 00136 /* Enhanced AC-3 */ 00137 skip_bits(gbc, 5); // skip bitstream id 00138 00139 /* skip dialog normalization and compression gain */ 00140 for (i = 0; i < (hdr->channel_mode ? 1 : 2); i++) { 00141 skip_bits(gbc, 5); // skip dialog normalization 00142 if (get_bits1(gbc)) { 00143 skip_bits(gbc, 8); //skip Compression gain word 00144 } 00145 } 00146 /* dependent stream channel map */ 00147 if (hdr->frame_type == EAC3_FRAME_TYPE_DEPENDENT && get_bits1(gbc)) { 00148 hdr->channel_map = get_bits(gbc, 16); //custom channel map 00149 return 0; 00150 } 00151 } 00152 //default channel map based on acmod and lfeon 00153 hdr->channel_map = ff_eac3_default_chmap[hdr->channel_mode]; 00154 if(hdr->lfe_on) 00155 hdr->channel_map |= AC3_CHMAP_LFE; 00156 } 00157 return ret; 00158 } 00159 00160 static int ac3_sync(uint64_t state, AACAC3ParseContext *hdr_info, 00161 int *need_next_header, int *new_frame_start) 00162 { 00163 int err; 00164 union { 00165 uint64_t u64; 00166 uint8_t u8[8]; 00167 } tmp = { be2me_64(state) }; 00168 AC3HeaderInfo hdr; 00169 GetBitContext gbc; 00170 00171 init_get_bits(&gbc, tmp.u8+8-AC3_HEADER_SIZE, 54); 00172 err = ff_ac3_parse_header(&gbc, &hdr); 00173 00174 if(err < 0) 00175 return 0; 00176 00177 hdr_info->sample_rate = hdr.sample_rate; 00178 hdr_info->bit_rate = hdr.bit_rate; 00179 hdr_info->channels = hdr.channels; 00180 hdr_info->channel_layout = hdr.channel_layout; 00181 hdr_info->samples = hdr.num_blocks * 256; 00182 if(hdr.bitstream_id>10) 00183 hdr_info->codec_id = CODEC_ID_EAC3; 00184 else if (hdr_info->codec_id == CODEC_ID_NONE) 00185 hdr_info->codec_id = CODEC_ID_AC3; 00186 00187 *need_next_header = (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT); 00188 *new_frame_start = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT); 00189 return hdr.frame_size; 00190 } 00191 00192 static av_cold int ac3_parse_init(AVCodecParserContext *s1) 00193 { 00194 AACAC3ParseContext *s = s1->priv_data; 00195 s->header_size = AC3_HEADER_SIZE; 00196 s->sync = ac3_sync; 00197 return 0; 00198 } 00199 00200 00201 AVCodecParser ac3_parser = { 00202 { CODEC_ID_AC3, CODEC_ID_EAC3 }, 00203 sizeof(AACAC3ParseContext), 00204 ac3_parse_init, 00205 ff_aac_ac3_parse, 00206 ff_parse_close, 00207 };