libavcodec/ac3_parser.c

   1 /*
   2  * AC-3 parser
   3  * Copyright (c) 2003 Fabrice Bellard
   4  * Copyright (c) 2003 Michael Niedermayer
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include "parser.h"
  24 #include "ac3_parser.h"
  25 #include "aac_ac3_parser.h"
  26 #include "get_bits.h"
  27
  28
  29 #define AC3_HEADER_SIZE 7
  30
  31
  32 static const uint8_t eac3_blocks[4] = {
  33     1, 2, 3, 6
  34 };
  35
  36
  37 int ff_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
  38 {
  39     int frame_size_code;
  40
  41     memset(hdr, 0, sizeof(*hdr));
  42
  43     hdr->sync_word = get_bits(gbc, 16);
  44     if(hdr->sync_word != 0x0B77)
  45         return AAC_AC3_PARSE_ERROR_SYNC;
  46
  47     /* read ahead to bsid to distinguish between AC-3 and E-AC-3 */
  48     hdr->bitstream_id = show_bits_long(gbc, 29) & 0x1F;
  49     if(hdr->bitstream_id > 16)
  50         return AAC_AC3_PARSE_ERROR_BSID;
  51
  52     hdr->num_blocks = 6;
  53
  54     /* set default mix levels */
  55     hdr->center_mix_level   = 1;  // -4.5dB
  56     hdr->surround_mix_level = 1;  // -6.0dB
  57
  58     if(hdr->bitstream_id <= 10) {
  59         /* Normal AC-3 */
  60         hdr->crc1 = get_bits(gbc, 16);
  61         hdr->sr_code = get_bits(gbc, 2);
  62         if(hdr->sr_code == 3)
  63             return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
  64
  65         frame_size_code = get_bits(gbc, 6);
  66         if(frame_size_code > 37)
  67             return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
  68
  69         skip_bits(gbc, 5); // skip bsid, already got it
  70
  71         skip_bits(gbc, 3); // skip bitstream mode
  72         hdr->channel_mode = get_bits(gbc, 3);
  73
  74         if(hdr->channel_mode == AC3_CHMODE_STEREO) {
  75             skip_bits(gbc, 2); // skip dsurmod
  76         } else {
  77             if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO)
  78                 hdr->center_mix_level = get_bits(gbc, 2);
  79             if(hdr->channel_mode & 4)
  80                 hdr->surround_mix_level = get_bits(gbc, 2);
  81         }
  82         hdr->lfe_on = get_bits1(gbc);
  83
  84         hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8;
  85         hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;
  86         hdr->bit_rate = (ff_ac3_bitrate_tab[frame_size_code>>1] * 1000) >> hdr->sr_shift;
  87         hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
  88         hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2;
  89         hdr->frame_type = EAC3_FRAME_TYPE_AC3_CONVERT; //EAC3_FRAME_TYPE_INDEPENDENT;
  90         hdr->substreamid = 0;
  91     } else {
  92         /* Enhanced AC-3 */
  93         hdr->crc1 = 0;
  94         hdr->frame_type = get_bits(gbc, 2);
  95         if(hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)
  96             return AAC_AC3_PARSE_ERROR_FRAME_TYPE;
  97
  98         hdr->substreamid = get_bits(gbc, 3);
  99
 100         hdr->frame_size = (get_bits(gbc, 11) + 1) << 1;
 101         if(hdr->frame_size < AC3_HEADER_SIZE)
 102             return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
 103
 104         hdr->sr_code = get_bits(gbc, 2);
 105         if (hdr->sr_code == 3) {
 106             int sr_code2 = get_bits(gbc, 2);
 107             if(sr_code2 == 3)
 108                 return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
 109             hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
 110             hdr->sr_shift = 1;
 111         } else {
 112             hdr->num_blocks = eac3_blocks[get_bits(gbc, 2)];
 113             hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code];
 114             hdr->sr_shift = 0;
 115         }
 116
 117         hdr->channel_mode = get_bits(gbc, 3);
 118         hdr->lfe_on = get_bits1(gbc);
 119
 120         hdr->bit_rate = (uint32_t)(8.0 * hdr->frame_size * hdr->sample_rate /
 121                         (hdr->num_blocks * 256.0));
 122         hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
 123     }
 124     hdr->channel_layout = ff_ac3_channel_layout_tab[hdr->channel_mode];
 125     if (hdr->lfe_on)
 126         hdr->channel_layout |= CH_LOW_FREQUENCY;
 127
 128     return 0;
 129 }
 130
 131 int ff_ac3_parse_header_full(GetBitContext *gbc, AC3HeaderInfo *hdr){
 132     int ret, i;
 133     ret = ff_ac3_parse_header(gbc, hdr);
 134     if(!ret){
 135         if(hdr->bitstream_id>10){
 136             /* Enhanced AC-3 */
 137             skip_bits(gbc, 5); // skip bitstream id
 138
 139             /* skip dialog normalization and compression gain */
 140             for (i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
 141                 skip_bits(gbc, 5); // skip dialog normalization
 142                 if (get_bits1(gbc)) {
 143                     skip_bits(gbc, 8); //skip Compression gain word
 144                 }
 145             }
 146             /* dependent stream channel map */
 147             if (hdr->frame_type == EAC3_FRAME_TYPE_DEPENDENT && get_bits1(gbc)) {
 148                     hdr->channel_map = get_bits(gbc, 16); //custom channel map
 149                     return 0;
 150             }
 151         }
 152         //default channel map based on acmod and lfeon
 153         hdr->channel_map = ff_eac3_default_chmap[hdr->channel_mode];
 154         if(hdr->lfe_on)
 155             hdr->channel_map |= AC3_CHMAP_LFE;
 156     }
 157     return ret;
 158 }
 159
 160 static int ac3_sync(uint64_t state, AACAC3ParseContext *hdr_info,
 161         int *need_next_header, int *new_frame_start)
 162 {
 163     int err;
 164     union {
 165         uint64_t u64;
 166         uint8_t  u8[8];
 167     } tmp = { be2me_64(state) };
 168     AC3HeaderInfo hdr;
 169     GetBitContext gbc;
 170
 171     init_get_bits(&gbc, tmp.u8+8-AC3_HEADER_SIZE, 54);
 172     err = ff_ac3_parse_header(&gbc, &hdr);
 173
 174     if(err < 0)
 175         return 0;
 176
 177     hdr_info->sample_rate = hdr.sample_rate;
 178     hdr_info->bit_rate = hdr.bit_rate;
 179     hdr_info->channels = hdr.channels;
 180     hdr_info->channel_layout = hdr.channel_layout;
 181     hdr_info->samples = hdr.num_blocks * 256;
 182     if(hdr.bitstream_id>10)
 183         hdr_info->codec_id = CODEC_ID_EAC3;
 184     else
 185         hdr_info->codec_id = CODEC_ID_AC3;
 186
 187     *need_next_header = (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);
 188     *new_frame_start  = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT);
 189     return hdr.frame_size;
 190 }
 191
 192 static av_cold int ac3_parse_init(AVCodecParserContext *s1)
 193 {
 194     AACAC3ParseContext *s = s1->priv_data;
 195     s->header_size = AC3_HEADER_SIZE;
 196     s->sync = ac3_sync;
 197     return 0;
 198 }
 199
 200
 201 AVCodecParser ac3_parser = {
 202     { CODEC_ID_AC3, CODEC_ID_EAC3 },
 203     sizeof(AACAC3ParseContext),
 204     ac3_parse_init,
 205     ff_aac_ac3_parse,
 206     ff_parse_close,
 207 };