mirror of
https://gitlab.com/mbunkus/mkvtoolnix.git
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101 lines
2.6 KiB
C++
101 lines
2.6 KiB
C++
/*
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mkvmerge -- utility for splicing together matroska files
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from component media subtypes
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ac3_common.cpp
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Written by Moritz Bunkus <moritz@bunkus.org>
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Distributed under the GPL
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see the file COPYING for details
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or visit http://www.gnu.org/copyleft/gpl.html
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*/
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/*!
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\file
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\version \$Id: ac3_common.cpp,v 1.2 2003/02/16 17:04:38 mosu Exp $
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\brief helper function for AC3 data
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\author Moritz Bunkus <moritz @ bunkus.org>
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*/
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#include <malloc.h>
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#include <string.h>
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#include "ac3_common.h"
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int find_ac3_header(unsigned char *buf, int size, ac3_header_t *ac3_header) {
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static int rate[] = { 32, 40, 48, 56, 64, 80, 96, 112, 128, 160,
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192, 224, 256, 320, 384, 448, 512, 576, 640};
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static unsigned char lfeon[8] = {0x10, 0x10, 0x04, 0x04, 0x04, 0x01,
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0x04, 0x01};
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static unsigned char halfrate[12] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3};
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ac3_header_t header;
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int i;
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int frmsizecod;
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int bitrate;
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int half;
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int acmod;
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for (i = 0; i < (size - 7); i++) {
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if ((buf[i] != 0x0b) || (buf[i + 1] != 0x77))
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continue;
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if (buf[i + 5] >= 0x60)
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continue;
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half = halfrate[buf[i + 5] >> 3];
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acmod = buf[i + 6] >> 5;
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header.flags = ((((buf[i + 6] & 0xf8) == 0x50) ? A52_DOLBY : acmod) |
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((buf[i + 6] & lfeon[acmod]) ? A52_LFE : 0));
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frmsizecod = buf[i + 4] & 63;
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if (frmsizecod >= 38)
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return -1;
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bitrate = rate[frmsizecod >> 1];
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header.bit_rate = (bitrate * 1000) >> half;
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switch (buf[i + 4] & 0xc0) {
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case 0:
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header.sample_rate = 48000 >> half;
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header.bytes = 4 * bitrate;
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break;
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case 0x40:
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header.sample_rate = 44100 >> half;
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header.bytes = 2 * (320 * bitrate / 147 + (frmsizecod & 1));
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break;
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case 0x80:
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header.sample_rate = 32000 >> half;
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header.bytes = 6 * bitrate;
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break;
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default:
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return -1;
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}
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switch(header.flags & A52_CHANNEL_MASK) {
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case A52_MONO:
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header.channels=1;
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break;
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case A52_CHANNEL:
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case A52_STEREO:
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case A52_CHANNEL1:
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case A52_CHANNEL2:
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case A52_DOLBY:
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header.channels=2;
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break;
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case A52_2F1R:
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case A52_3F:
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header.channels=3;
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break;
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case A52_3F1R:
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case A52_2F2R:
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header.channels=4;
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break;
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case A52_3F2R:
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header.channels=5;
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break;
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}
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if (header.flags & A52_LFE)
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header.channels++;
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memcpy(ac3_header, &header, sizeof(ac3_header_t));
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return i;
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}
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return -1;
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}
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