mkvtoolnix/aac_common.cpp

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/*
mkvmerge -- utility for splicing together matroska files
from component media subtypes
aac_common.cpp
Written by Moritz Bunkus <moritz@bunkus.org>
Distributed under the GPL
see the file COPYING for details
or visit http://www.gnu.org/copyleft/gpl.html
*/
/*!
\file
\version \$Id: aac_common.cpp,v 1.5 2003/05/19 20:51:12 mosu Exp $
\brief helper function for AAC data
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\author Moritz Bunkus <moritz@bunkus.org>
*/
#include <stdio.h>
#include <string.h>
#include "common.h"
#include "aac_common.h"
static const int sample_rates[16] = {96000, 88200, 64000, 48000, 44100, 32000,
24000, 22050, 16000, 12000, 11025, 8000,
0, 0, 0, 0}; // filling
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int parse_aac_adif_header(unsigned char *buf, int size,
aac_header_t *aac_header) {
int i, k;
bool b, eob;
unsigned int bits;
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int nprogram_conf_e, bitstream_type, profile, sfreq_index;
int nfront_c_e, nside_c_e, nback_c_e, nlfe_c_e;
int nassoc_data_e, nvalid_cc_e, comment_field_bytes;
int channels;
bit_cursor_c bc(buf, size);
bc.get_bits(32, bits);
if (bits != FOURCC('A', 'D', 'I', 'F'))
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return 0;
bc.get_bit(b); // copyright_id_present
if (b) {
for (i = 0; i < 3; i++)
eob = bc.get_bits(24, bits); // copyright_id
}
bc.get_bit(b); // original_copy
bc.get_bit(b); // home
bc.get_bits(1, bitstream_type);
bc.get_bits(23, bits); // bitrate
bc.get_bits(4, nprogram_conf_e);
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for (i = 0; i <= nprogram_conf_e; i++) {
channels = 0;
if (bitstream_type == 0)
bc.get_bits(20, bits);
bc.get_bits(4, bits); // element_instance_tag
bc.get_bits(2, profile);
bc.get_bits(4, sfreq_index);
bc.get_bits(4, nfront_c_e);
bc.get_bits(4, nside_c_e);
bc.get_bits(4, nback_c_e);
bc.get_bits(2, nlfe_c_e);
bc.get_bits(3, nassoc_data_e);
bc.get_bits(4, nvalid_cc_e);
bc.get_bit(b); // mono_mixdown_present
if (b)
bc.get_bits(4, bits); // mono_mixdown_el_num
bc.get_bit(b); // stereo_mixdown_present
if (b)
bc.get_bits(4, bits); // stereo_mixdown_el_num
bc.get_bit(b); // matrix_mixdown_idx_present
if (b) {
bc.get_bits(2, bits); // matrix_mixdown_idx
eob = bc.get_bits(1, bits); // pseudo_surround_enable
}
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channels = nfront_c_e + nside_c_e + nback_c_e;
for (k = 0; k < (nfront_c_e + nside_c_e + nback_c_e); k++) {
bc.get_bit(b); // *_element_is_cpe
if (b)
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channels++;
bc.get_bits(4, bits); // *_element_tag_select
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}
channels += nlfe_c_e;
for (k = 0; k < (nlfe_c_e + nassoc_data_e); k++)
bc.get_bits(4, bits); // *_element_tag_select
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for (k = 0; k < nvalid_cc_e; k++) {
bc.get_bits(1, bits); // cc_e_is_ind_sw
bc.get_bits(4, bits); // valid_cc_e_tag_select
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}
bc.byte_align();
eob = bc.get_bits(8, bits);
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for (k = 0; k < comment_field_bytes; k++)
eob = bc.get_bits(8, bits);
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}
if (eob)
return 0;
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aac_header->sample_rate = sample_rates[sfreq_index];
aac_header->id = 0; // MPEG-4
aac_header->profile = profile;
aac_header->bytes = 0;
aac_header->channels = channels > 6 ? 2 : channels;
aac_header->bit_rate = 1024;
aac_header->header_bit_size = bc.get_bit_position();
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aac_header->header_byte_size = (aac_header->header_bit_size + 7) / 8;
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return 1;
}
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static int is_adts_header(unsigned char *buf, int size, int bpos,
aac_header_t *aac_header) {
int id, profile, sfreq_index, channels, frame_length;
bool eob, protection_absent, b;
unsigned int bits;
bit_cursor_c bc(buf, size);
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bc.get_bits(12, bits);
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if (bits != 0xfff) // ADTS header
return 0;
bc.get_bits(1, id); // ID: 0 = MPEG-4, 1 = MPEG-2
bc.get_bits(2, bits); // layer: = 0 !!
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if (bits != 0)
return 0;
bc.get_bit(protection_absent);
bc.get_bits(2, profile);
bc.get_bits(4, sfreq_index);
bc.get_bit(b); // private
bc.get_bits(3, channels);
bc.get_bit(b); // original/copy
bc.get_bit(b); // home
if (id == 0)
bc.get_bits(2, bits); // emphasis, MPEG-4 only
bc.get_bit(b); // copyright_id_bit
bc.get_bit(b); // copyright_id_start
bc.get_bits(13, frame_length);
bc.get_bits(11, bits); // adts_buffer_fullness
eob = bc.get_bits(2, bits); // no_raw_blocks_in_frame
if (!protection_absent)
eob = bc.get_bits(16, bits);
if (eob)
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return 0;
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aac_header->sample_rate = sample_rates[sfreq_index];
aac_header->id = id;
aac_header->profile = profile;
aac_header->bytes = frame_length;
aac_header->channels = channels > 6 ? 2 : channels;
aac_header->bit_rate = 1024;
if (id == 0) // MPEG-4
aac_header->header_bit_size = 58;
else
aac_header->header_bit_size = 56;
if (!protection_absent)
aac_header->header_bit_size += 16;
aac_header->header_byte_size = (aac_header->header_bit_size + 7) / 8;
aac_header->data_byte_size = aac_header->bytes -
aac_header->header_bit_size / 8;
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return 1;
}
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int find_aac_header(unsigned char *buf, int size, aac_header_t *aac_header) {
int bpos;
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bpos = 0;
while (bpos < size) {
if (is_adts_header(buf, size, bpos, aac_header))
return bpos;
bpos++;
}
return -1;
}