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 Libav.
   7  *
   8  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include "libavutil/channel_layout.h"
  24 #include "parser.h"
  25 #include "ac3_parser.h"
  26 #include "aac_ac3_parser.h"
  27 #include "get_bits.h"
  28
  29
  30 #define AC3_HEADER_SIZE 7
  31
  32
  33 static const uint8_t eac3_blocks[4] = {
  34     1, 2, 3, 6
  35 };
  36
  37 /**
  38  * Table for center mix levels
  39  * reference: Section 5.4.2.4 cmixlev
  40  */
  41 static const uint8_t center_levels[4] = { 4, 5, 6, 5 };
  42
  43 /**
  44  * Table for surround mix levels
  45  * reference: Section 5.4.2.5 surmixlev
  46  */
  47 static const uint8_t surround_levels[4] = { 4, 6, 7, 6 };
  48
  49
  50 int avpriv_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
  51 {
  52     int frame_size_code;
  53
  54     memset(hdr, 0, sizeof(*hdr));
  55
  56     hdr->sync_word = get_bits(gbc, 16);
  57     if(hdr->sync_word != 0x0B77)
  58         return AAC_AC3_PARSE_ERROR_SYNC;
  59
  60     /* read ahead to bsid to distinguish between AC-3 and E-AC-3 */
  61     hdr->bitstream_id = show_bits_long(gbc, 29) & 0x1F;
  62     if(hdr->bitstream_id > 16)
  63         return AAC_AC3_PARSE_ERROR_BSID;
  64
  65     hdr->num_blocks = 6;
  66
  67     /* set default mix levels */
  68     hdr->center_mix_level   = 5;  // -4.5dB
  69     hdr->surround_mix_level = 6;  // -6.0dB
  70
  71     if(hdr->bitstream_id <= 10) {
  72         /* Normal AC-3 */
  73         hdr->crc1 = get_bits(gbc, 16);
  74         hdr->sr_code = get_bits(gbc, 2);
  75         if(hdr->sr_code == 3)
  76             return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
  77
  78         frame_size_code = get_bits(gbc, 6);
  79         if(frame_size_code > 37)
  80             return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
  81
  82         skip_bits(gbc, 5); // skip bsid, already got it
  83
  84         hdr->bitstream_mode = get_bits(gbc, 3);
  85         hdr->channel_mode = get_bits(gbc, 3);
  86
  87         if(hdr->channel_mode == AC3_CHMODE_STEREO) {
  88             skip_bits(gbc, 2); // skip dsurmod
  89         } else {
  90             if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO)
  91                 hdr->  center_mix_level =   center_levels[get_bits(gbc, 2)];
  92             if(hdr->channel_mode & 4)
  93                 hdr->surround_mix_level = surround_levels[get_bits(gbc, 2)];
  94         }
  95         hdr->lfe_on = get_bits1(gbc);
  96
  97         hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8;
  98         hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;
  99         hdr->bit_rate = (ff_ac3_bitrate_tab[frame_size_code>>1] * 1000) >> hdr->sr_shift;
 100         hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
 101         hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2;
 102         hdr->frame_type = EAC3_FRAME_TYPE_AC3_CONVERT; //EAC3_FRAME_TYPE_INDEPENDENT;
 103         hdr->substreamid = 0;
 104     } else {
 105         /* Enhanced AC-3 */
 106         hdr->crc1 = 0;
 107         hdr->frame_type = get_bits(gbc, 2);
 108         if(hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)
 109             return AAC_AC3_PARSE_ERROR_FRAME_TYPE;
 110
 111         hdr->substreamid = get_bits(gbc, 3);
 112
 113         hdr->frame_size = (get_bits(gbc, 11) + 1) << 1;
 114         if(hdr->frame_size < AC3_HEADER_SIZE)
 115             return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
 116
 117         hdr->sr_code = get_bits(gbc, 2);
 118         if (hdr->sr_code == 3) {
 119             int sr_code2 = get_bits(gbc, 2);
 120             if(sr_code2 == 3)
 121                 return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
 122             hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
 123             hdr->sr_shift = 1;
 124         } else {
 125             hdr->num_blocks = eac3_blocks[get_bits(gbc, 2)];
 126             hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code];
 127             hdr->sr_shift = 0;
 128         }
 129
 130         hdr->channel_mode = get_bits(gbc, 3);
 131         hdr->lfe_on = get_bits1(gbc);
 132
 133         hdr->bit_rate = (uint32_t)(8.0 * hdr->frame_size * hdr->sample_rate /
 134                         (hdr->num_blocks * 256.0));
 135         hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
 136     }
 137     hdr->channel_layout = avpriv_ac3_channel_layout_tab[hdr->channel_mode];
 138     if (hdr->lfe_on)
 139         hdr->channel_layout |= AV_CH_LOW_FREQUENCY;
 140
 141     return 0;
 142 }
 143
 144 static int ac3_sync(uint64_t state, AACAC3ParseContext *hdr_info,
 145         int *need_next_header, int *new_frame_start)
 146 {
 147     int err;
 148     union {
 149         uint64_t u64;
 150         uint8_t  u8[8];
 151     } tmp = { av_be2ne64(state) };
 152     AC3HeaderInfo hdr;
 153     GetBitContext gbc;
 154
 155     init_get_bits(&gbc, tmp.u8+8-AC3_HEADER_SIZE, 54);
 156     err = avpriv_ac3_parse_header(&gbc, &hdr);
 157
 158     if(err < 0)
 159         return 0;
 160
 161     hdr_info->sample_rate = hdr.sample_rate;
 162     hdr_info->bit_rate = hdr.bit_rate;
 163     hdr_info->channels = hdr.channels;
 164     hdr_info->channel_layout = hdr.channel_layout;
 165     hdr_info->samples = hdr.num_blocks * 256;
 166     hdr_info->service_type = hdr.bitstream_mode;
 167     if (hdr.bitstream_mode == 0x7 && hdr.channels > 1)
 168         hdr_info->service_type = AV_AUDIO_SERVICE_TYPE_KARAOKE;
 169     if(hdr.bitstream_id>10)
 170         hdr_info->codec_id = AV_CODEC_ID_EAC3;
 171     else if (hdr_info->codec_id == AV_CODEC_ID_NONE)
 172         hdr_info->codec_id = AV_CODEC_ID_AC3;
 173
 174     *need_next_header = (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);
 175     *new_frame_start  = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT);
 176     return hdr.frame_size;
 177 }
 178
 179 static av_cold int ac3_parse_init(AVCodecParserContext *s1)
 180 {
 181     AACAC3ParseContext *s = s1->priv_data;
 182     s->header_size = AC3_HEADER_SIZE;
 183     s->sync = ac3_sync;
 184     return 0;
 185 }
 186
 187
 188 AVCodecParser ff_ac3_parser = {
 189     .codec_ids      = { AV_CODEC_ID_AC3, AV_CODEC_ID_EAC3 },
 190     .priv_data_size = sizeof(AACAC3ParseContext),
 191     .parser_init    = ac3_parse_init,
 192     .parser_parse   = ff_aac_ac3_parse,
 193     .parser_close   = ff_parse_close,
 194 };