/* * AC3 parser * Copyright (c) 2003 Fabrice Bellard. * Copyright (c) 2003 Michael Niedermayer. * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #include "parser.h" #include "ac3_parser.h" #include "aac_ac3_parser.h" #include "bitstream.h" #define AC3_HEADER_SIZE 7 static const uint8_t eac3_blocks[4] = { 1, 2, 3, 6 }; /** * Table for center mix levels * reference: Section 5.4.2.4 cmixlev */ static const uint8_t center_levels[4] = { 2, 3, 4, 3 }; /** * Table for surround mix levels * reference: Section 5.4.2.5 surmixlev */ static const uint8_t surround_levels[4] = { 2, 4, 0, 4 }; int ff_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr) { int frame_size_code; int num_blocks; memset(hdr, 0, sizeof(*hdr)); hdr->sync_word = get_bits(gbc, 16); if(hdr->sync_word != 0x0B77) return AC3_PARSE_ERROR_SYNC; /* read ahead to bsid to distinguish between AC-3 and E-AC-3 */ hdr->bitstream_id = show_bits_long(gbc, 29) & 0x1F; if(hdr->bitstream_id > 16) return AC3_PARSE_ERROR_BSID; if(hdr->bitstream_id <= 10) { /* Normal AC-3 */ hdr->crc1 = get_bits(gbc, 16); hdr->sr_code = get_bits(gbc, 2); if(hdr->sr_code == 3) return AC3_PARSE_ERROR_SAMPLE_RATE; frame_size_code = get_bits(gbc, 6); if(frame_size_code > 37) return AC3_PARSE_ERROR_FRAME_SIZE; skip_bits(gbc, 5); // skip bsid, already got it skip_bits(gbc, 3); // skip bitstream mode hdr->channel_mode = get_bits(gbc, 3); /* set default mix levels */ hdr->center_mix_level = 3; // -4.5dB hdr->surround_mix_level = 4; // -6.0dB if(hdr->channel_mode == AC3_CHMODE_STEREO) { skip_bits(gbc, 2); // skip dsurmod } else { if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO) hdr->center_mix_level = center_levels[get_bits(gbc, 2)]; if(hdr->channel_mode & 4) hdr->surround_mix_level = surround_levels[get_bits(gbc, 2)]; } hdr->lfe_on = get_bits1(gbc); hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8; hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift; hdr->bit_rate = (ff_ac3_bitrate_tab[frame_size_code>>1] * 1000) >> hdr->sr_shift; hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on; hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2; hdr->frame_type = EAC3_FRAME_TYPE_AC3_CONVERT; //EAC3_FRAME_TYPE_INDEPENDENT; } else { /* Enhanced AC-3 */ hdr->crc1 = 0; hdr->frame_type = get_bits(gbc, 2); if(hdr->frame_type == EAC3_FRAME_TYPE_RESERVED) return AC3_PARSE_ERROR_FRAME_TYPE; skip_bits(gbc, 3); // skip substream id hdr->frame_size = (get_bits(gbc, 11) + 1) << 1; if(hdr->frame_size < AC3_HEADER_SIZE) return AC3_PARSE_ERROR_FRAME_SIZE; hdr->sr_code = get_bits(gbc, 2); if (hdr->sr_code == 3) { int sr_code2 = get_bits(gbc, 2); if(sr_code2 == 3) return AC3_PARSE_ERROR_SAMPLE_RATE; hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2; hdr->sr_shift = 1; num_blocks = 6; } else { num_blocks = eac3_blocks[get_bits(gbc, 2)]; hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code]; hdr->sr_shift = 0; } hdr->channel_mode = get_bits(gbc, 3); hdr->lfe_on = get_bits1(gbc); hdr->bit_rate = (uint32_t)(8.0 * hdr->frame_size * hdr->sample_rate / (num_blocks * 256.0)); hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on; } return 0; } int ff_ac3_parse_header_full(GetBitContext *gbc, AC3HeaderInfo *hdr){ int ret, i; ret = ff_ac3_parse_header(gbc, hdr); if(!ret){ if(hdr->bitstream_id>10){ /* Enhanced AC-3 */ skip_bits(gbc, 5); // skip bitstream id /* skip dialog normalization and compression gain */ for (i = 0; i < (hdr->channel_mode ? 1 : 2); i++) { skip_bits(gbc, 5); // skip dialog normalization if (get_bits1(gbc)) { skip_bits(gbc, 8); //skip Compression gain word } } /* dependent stream channel map */ if (hdr->frame_type == EAC3_FRAME_TYPE_DEPENDENT && get_bits1(gbc)) { hdr->channel_map = get_bits(gbc, 16); //custom channel map return 0; } } //default channel map based on acmod and lfeon hdr->channel_map = ff_eac3_default_chmap[hdr->channel_mode]; if(hdr->lfe_on) hdr->channel_map |= AC3_CHMAP_LFE; } return ret; } static int ac3_sync(uint64_t state, AACAC3ParseContext *hdr_info, int *need_next_header, int *new_frame_start) { int err; uint64_t tmp = be2me_64(state); AC3HeaderInfo hdr; GetBitContext gbc; init_get_bits(&gbc, ((uint8_t *)&tmp)+8-AC3_HEADER_SIZE, 54); err = ff_ac3_parse_header(&gbc, &hdr); if(err < 0) return 0; hdr_info->sample_rate = hdr.sample_rate; hdr_info->bit_rate = hdr.bit_rate; hdr_info->channels = hdr.channels; hdr_info->samples = AC3_FRAME_SIZE; *need_next_header = (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT); *new_frame_start = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT); return hdr.frame_size; } static av_cold int ac3_parse_init(AVCodecParserContext *s1) { AACAC3ParseContext *s = s1->priv_data; s->header_size = AC3_HEADER_SIZE; s->sync = ac3_sync; return 0; } AVCodecParser ac3_parser = { { CODEC_ID_AC3 }, sizeof(AACAC3ParseContext), ac3_parse_init, ff_aac_ac3_parse, NULL, };