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/* |
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* MQ-coder decoder |
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* Copyright (c) 2007 Kamil Nowosad |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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/** |
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* MQ-coder decoder |
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* @file |
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* @author Kamil Nowosad |
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*/ |
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#include "mqc.h" |
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15972024 |
static void bytein(MqcState *mqc) |
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{ |
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✓✓ |
15972024 |
if (*mqc->bp == 0xff) { |
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✓✓ |
447940 |
if (*(mqc->bp + 1) > 0x8f) |
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385409 |
mqc->c++; |
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else { |
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62531 |
mqc->bp++; |
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62531 |
mqc->c += 2 + 0xfe00 - (*mqc->bp << 9); |
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} |
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} else { |
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15524084 |
mqc->bp++; |
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15524084 |
mqc->c += 1 + 0xff00 - (*mqc->bp << 8); |
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} |
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15972024 |
} |
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88273842 |
static int exchange(MqcState *mqc, uint8_t *cxstate, int lps) |
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{ |
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int d; |
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✓✓ |
88273842 |
if ((mqc->a < ff_mqc_qe[*cxstate]) ^ (!lps)) { |
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✓✓ |
46699411 |
if (lps) |
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8992607 |
mqc->a = ff_mqc_qe[*cxstate]; |
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46699411 |
d = *cxstate & 1; |
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46699411 |
*cxstate = ff_mqc_nmps[*cxstate]; |
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} else { |
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✓✓ |
41574431 |
if (lps) |
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34304675 |
mqc->a = ff_mqc_qe[*cxstate]; |
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41574431 |
d = 1 - (*cxstate & 1); |
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41574431 |
*cxstate = ff_mqc_nlps[*cxstate]; |
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} |
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// do RENORMD: see ISO/IEC 15444-1:2002 §C.3.3 |
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do { |
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✓✓ |
124024020 |
if (!(mqc->c & 0xff)) { |
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15609296 |
mqc->c -= 0x100; |
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15609296 |
bytein(mqc); |
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} |
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124024020 |
mqc->a += mqc->a; |
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124024020 |
mqc->c += mqc->c; |
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✓✓ |
124024020 |
} while (!(mqc->a & 0x8000)); |
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88273842 |
return d; |
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} |
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362728 |
void ff_mqc_initdec(MqcState *mqc, uint8_t *bp, int raw, int reset) |
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{ |
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362728 |
mqc->raw = raw; |
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✓✗ |
362728 |
if (reset) |
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362728 |
ff_mqc_init_contexts(mqc); |
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362728 |
mqc->bp = bp; |
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362728 |
mqc->c = (*mqc->bp ^ 0xff) << 16; |
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362728 |
bytein(mqc); |
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362728 |
mqc->c = mqc->c << 7; |
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362728 |
mqc->a = 0x8000; |
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362728 |
} |
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static int mqc_decode_bypass(MqcState *mqc) { |
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int bit = !(mqc->c & 0x40000000); |
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if (!(mqc->c & 0xff)) { |
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mqc->c -= 0x100; |
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bytein(mqc); |
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} |
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mqc->c += mqc->c; |
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return bit; |
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} |
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182845733 |
int ff_mqc_decode(MqcState *mqc, uint8_t *cxstate) |
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{ |
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✗✓ |
182845733 |
if (mqc->raw) |
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return mqc_decode_bypass(mqc); |
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182845733 |
mqc->a -= ff_mqc_qe[*cxstate]; |
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✓✓ |
182845733 |
if ((mqc->c >> 16) < mqc->a) { |
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✓✓ |
139548451 |
if (mqc->a & 0x8000) |
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94571891 |
return *cxstate & 1; |
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else |
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44976560 |
return exchange(mqc, cxstate, 0); |
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} else { |
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43297282 |
mqc->c -= mqc->a << 16; |
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43297282 |
return exchange(mqc, cxstate, 1); |
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} |
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} |