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/*
* 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;
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;
hdr->num_blocks = 6;
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;
} else {
hdr->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 /
(hdr->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,
};
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