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FFmpeg/libavcodec/ac3_parser.c

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/*
* AC-3 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 "config_components.h"
#include "libavutil/channel_layout.h"
#include "libavutil/mem.h"
#include "parser.h"
#include "ac3defs.h"
#include "ac3tab.h"
#include "ac3_parser.h"
#include "ac3_parser_internal.h"
#include "aac_ac3_parser.h"
#include "get_bits.h"
#define AC3_HEADER_SIZE 7
#if CONFIG_AC3_PARSER
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] = { 4, 5, 6, 5 };
/**
* Table for surround mix levels
* reference: Section 5.4.2.5 surmixlev
*/
static const uint8_t surround_levels[4] = { 4, 6, 7, 6 };
int ff_ac3_find_syncword(const uint8_t *buf, int buf_size)
{
int i;
for (i = 1; i < buf_size; i += 2) {
if (buf[i] == 0x77 || buf[i] == 0x0B) {
if ((buf[i] ^ buf[i-1]) == (0x77 ^ 0x0B)) {
i--;
break;
} else if ((buf[i] ^ buf[i+1]) == (0x77 ^ 0x0B)) {
break;
}
}
}
if (i >= buf_size)
return AVERROR_INVALIDDATA;
return i;
}
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 AAC_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 AAC_AC3_PARSE_ERROR_BSID;
hdr->num_blocks = 6;
hdr->ac3_bit_rate_code = -1;
/* set default mix levels */
hdr->center_mix_level = 5; // -4.5dB
hdr->surround_mix_level = 6; // -6.0dB
/* set default dolby surround mode */
hdr->dolby_surround_mode = AC3_DSURMOD_NOTINDICATED;
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 AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
frame_size_code = get_bits(gbc, 6);
if(frame_size_code > 37)
return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
hdr->ac3_bit_rate_code = (frame_size_code >> 1);
skip_bits(gbc, 5); // skip bsid, already got it
hdr->bitstream_mode = get_bits(gbc, 3);
hdr->channel_mode = get_bits(gbc, 3);
if(hdr->channel_mode == AC3_CHMODE_STEREO) {
hdr->dolby_surround_mode = get_bits(gbc, 2);
} 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[hdr->ac3_bit_rate_code] * 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;
hdr->substreamid = 0;
} else {
/* Enhanced AC-3 */
hdr->crc1 = 0;
hdr->frame_type = get_bits(gbc, 2);
if(hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)
return AAC_AC3_PARSE_ERROR_FRAME_TYPE;
hdr->substreamid = get_bits(gbc, 3);
hdr->frame_size = (get_bits(gbc, 11) + 1) << 1;
if(hdr->frame_size < AC3_HEADER_SIZE)
return AAC_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 AAC_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 = 8LL * hdr->frame_size * hdr->sample_rate /
(hdr->num_blocks * 256);
hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
}
hdr->channel_layout = ff_ac3_channel_layout_tab[hdr->channel_mode];
if (hdr->lfe_on)
hdr->channel_layout |= AV_CH_LOW_FREQUENCY;
return 0;
}
// TODO: Better way to pass AC3HeaderInfo fields to mov muxer.
int avpriv_ac3_parse_header(AC3HeaderInfo **phdr, const uint8_t *buf,
size_t size)
{
GetBitContext gb;
AC3HeaderInfo *hdr;
int err;
if (!*phdr)
*phdr = av_mallocz(sizeof(AC3HeaderInfo));
if (!*phdr)
return AVERROR(ENOMEM);
hdr = *phdr;
err = init_get_bits8(&gb, buf, size);
if (err < 0)
return AVERROR_INVALIDDATA;
err = ff_ac3_parse_header(&gb, hdr);
if (err < 0)
return AVERROR_INVALIDDATA;
return get_bits_count(&gb);
}
int av_ac3_parse_header(const uint8_t *buf, size_t size,
uint8_t *bitstream_id, uint16_t *frame_size)
{
GetBitContext gb;
AC3HeaderInfo hdr;
int err;
init_get_bits8(&gb, buf, size);
err = ff_ac3_parse_header(&gb, &hdr);
if (err < 0)
return AVERROR_INVALIDDATA;
*bitstream_id = hdr.bitstream_id;
*frame_size = hdr.frame_size;
return 0;
}
static int ac3_sync(uint64_t state, int *need_next_header, int *new_frame_start)
{
int err;
union {
uint64_t u64;
uint8_t u8[8 + AV_INPUT_BUFFER_PADDING_SIZE];
} tmp = { av_be2ne64(state) };
AC3HeaderInfo hdr;
GetBitContext gbc;
if (tmp.u8[1] == 0x77 && tmp.u8[2] == 0x0b) {
FFSWAP(uint8_t, tmp.u8[1], tmp.u8[2]);
FFSWAP(uint8_t, tmp.u8[3], tmp.u8[4]);
FFSWAP(uint8_t, tmp.u8[5], tmp.u8[6]);
}
init_get_bits(&gbc, tmp.u8+8-AC3_HEADER_SIZE, 54);
err = ff_ac3_parse_header(&gbc, &hdr);
if(err < 0)
return 0;
*new_frame_start = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT);
*need_next_header = *new_frame_start || (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);
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->crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);
s->sync = ac3_sync;
return 0;
}
const AVCodecParser ff_ac3_parser = {
.codec_ids = { AV_CODEC_ID_AC3, AV_CODEC_ID_EAC3 },
.priv_data_size = sizeof(AACAC3ParseContext),
.parser_init = ac3_parse_init,
.parser_parse = ff_aac_ac3_parse,
.parser_close = ff_parse_close,
};
#else
int avpriv_ac3_parse_header(AC3HeaderInfo **phdr, const uint8_t *buf,
size_t size)
{
return AVERROR(ENOSYS);
}
int av_ac3_parse_header(const uint8_t *buf, size_t size,
uint8_t *bitstream_id, uint16_t *frame_size)
{
return AVERROR(ENOSYS);
}
#endif