forked from osmocom/wireshark
123 lines
2.8 KiB
C
123 lines
2.8 KiB
C
/* mpeg-audio.c
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*
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* MPEG Audio header dissection
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* Written by Shaun Jackman <sjackman@gmail.com>
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* Copyright 2007 Shaun Jackman
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*
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* Wiretap Library
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* SPDX-License-Identifier: GPL-2.0-or-later
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*/
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#include "mpeg-audio.h"
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static const int mpa_versions[4] = { 2, -1, 1, 0 };
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static const int mpa_layers[4] = { -1, 2, 1, 0 };
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static const unsigned int mpa_samples_data[3][3] = {
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{ 384, 1152, 1152 },
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{ 384, 1152, 576 },
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{ 384, 1152, 576 },
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};
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static const unsigned int mpa_bitrates[3][3][16] = { /* kb/s */
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{
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{ 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448 },
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{ 0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384 },
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{ 0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320 },
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},
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{
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{ 0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256 },
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{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160 },
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{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160 },
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},
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{
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{ 0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256 },
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{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160 },
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{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160 },
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},
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};
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static const unsigned int mpa_frequencies[3][4] = {
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{ 44100, 48000, 32000 },
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{ 22050, 24000, 16000 },
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{ 11025, 12000, 8000 },
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};
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static const unsigned int mpa_padding_data[3] = { 4, 1, 1 };
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int
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mpa_version(const struct mpa *mpa)
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{
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return mpa_versions[mpa->version];
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}
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int
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mpa_layer(const struct mpa *mpa)
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{
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return mpa_layers[mpa->layer];
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}
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unsigned
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mpa_samples(const struct mpa *mpa)
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{
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return mpa_samples_data[mpa_versions[mpa->version]][mpa_layer(mpa)];
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}
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unsigned
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mpa_bitrate(const struct mpa *mpa)
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{
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return (1000 * (mpa_bitrates[mpa_versions[mpa->version]][mpa_layers[mpa->layer]][mpa->bitrate]));
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}
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unsigned
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mpa_frequency(const struct mpa *mpa)
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{
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return(mpa_frequencies[mpa_versions[mpa->version]][mpa->frequency]);
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}
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unsigned
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mpa_padding(const struct mpa *mpa)
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{
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return(mpa->padding ? mpa_padding_data[mpa_layers[mpa->layer]] : 0);
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}
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/* Decode an ID3v2 synchsafe integer.
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* See https://id3.org/id3v2.4.0-structure section 6.2.
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*/
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guint32
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decode_synchsafe_int(guint32 input)
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{
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guint32 value;
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/* High-order byte */
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value = (input >> 24) & 0x7f;
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/* Shift the result left to make room for the next 7 bits */
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value <<= 7;
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/* Now OR in the 2nd byte */
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value |= (input >> 16) & 0x7f;
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value <<= 7;
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/* ... and the 3rd */
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value |= (input >> 8) & 0x7f;
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value <<= 7;
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/* For the 4th byte don't do the shift */
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value |= input & 0x7f;
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return value;
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}
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/*
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* Editor modelines - https://www.wireshark.org/tools/modelines.html
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*
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* Local variables:
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* c-basic-offset: 8
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* tab-width: 8
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* indent-tabs-mode: t
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* End:
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*
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* vi: set shiftwidth=8 tabstop=8 noexpandtab:
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* :indentSize=8:tabSize=8:noTabs=false:
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*/
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