mirror of
https://gitlab.com/mbunkus/mkvtoolnix.git
synced 2024-12-25 20:32:33 +00:00
97 lines
2.4 KiB
C++
97 lines
2.4 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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mp3_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 $Id$
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\brief helper functions for MP3 data
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\author Moritz Bunkus <moritz@bunkus.org>
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*/
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#include "mp3_common.h"
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#include "common.h"
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int mp3_tabsel[2][16] =
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{{0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320},
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{0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160}};
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long mp3_freqs[9] =
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{44100, 48000, 32000, 22050, 24000, 16000, 11025, 12000, 8000};
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int find_mp3_header(unsigned char *buf, int size, unsigned long *_header) {
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int i, pos;
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unsigned long header;
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if (size < 4)
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return -1;
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for (pos = 0; pos <= (size - 4); pos++) {
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for (i = 0, header = 0; i < 4; i++) {
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header <<= 8;
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header |= buf[i + pos];
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}
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if ((header == FOURCC('R', 'I', 'F', 'F')) ||
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((header & 0xffffff00) == FOURCC('I', 'D', '3', ' ')))
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continue;
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if ((header & 0xffe00000) != 0xffe00000)
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continue;
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if (!((header >> 17) & 3))
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continue;
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if (((header >> 12) & 0xf) == 0xf)
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continue;
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if (!((header >> 12) & 0xf))
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continue;
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if (((header >> 10) & 0x3) == 0x3)
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continue;
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if ((((header >> 19) & 1) == 1) && (((header >> 17) & 3) == 3) &&
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(((header >> 16) & 1) == 1))
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continue;
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if ((header & 0xffff0000) == 0xfffe0000)
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continue;
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*_header = header;
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return pos;
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}
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return -1;
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}
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void decode_mp3_header(unsigned long header, mp3_header_t *h) {
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if (header & (1 << 20)) {
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h->lsf = (header & (1 << 19)) ? 0 : 1;
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h->mpeg25 = 0;
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} else {
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h->lsf = 1;
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h->mpeg25 = 1;
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}
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h->mode = (header >> 6) & 3;
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h->error_protection = ((header >> 16) & 1) ^ 1;
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h->stereo = (h->mode == 3 ? 0 : 1);
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if (h->lsf)
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h->ssize = (h->stereo == 1 ? 9 : 17);
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else
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h->ssize = (h->stereo == 1 ? 17: 32);
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if (h->error_protection)
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h->ssize += 2;
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h->bitrate_index = (header >> 12) & 15;
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if (h->mpeg25)
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h->sampling_frequency = 6 + ((header >> 10) & 3);
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else
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h->sampling_frequency = ((header >> 10) & 3) + (h->lsf * 3);
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h->padding = (header >> 9) & 1;
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h->framesize = (long)mp3_tabsel[h->lsf][h->bitrate_index] * 144000;
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h->framesize /= (mp3_freqs[h->sampling_frequency] << h->lsf);
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h->framesize = h->framesize + h->padding - 4;
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}
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