0,0 → 1,93 |
/* |
* MQ-coder decoder |
* Copyright (c) 2007 Kamil Nowosad |
* |
* This file is part of FFmpeg. |
* |
* FFmpeg is free software; you can redistribute it and/or |
* modify it under the terms of the GNU Lesser General Public |
* License as published by the Free Software Foundation; either |
* version 2.1 of the License, or (at your option) any later version. |
* |
* FFmpeg is distributed in the hope that it will be useful, |
* but WITHOUT ANY WARRANTY; without even the implied warranty of |
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
* Lesser General Public License for more details. |
* |
* You should have received a copy of the GNU Lesser General Public |
* License along with FFmpeg; if not, write to the Free Software |
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
*/ |
|
/** |
* MQ-coder decoder |
* @file |
* @author Kamil Nowosad |
*/ |
|
#include "mqc.h" |
|
static void bytein(MqcState *mqc) |
{ |
if (*mqc->bp == 0xff) { |
if (*(mqc->bp + 1) > 0x8f) |
mqc->c++; |
else { |
mqc->bp++; |
mqc->c += 2 + 0xfe00 - (*mqc->bp << 9); |
} |
} else { |
mqc->bp++; |
mqc->c += 1 + 0xff00 - (*mqc->bp << 8); |
} |
} |
|
static int exchange(MqcState *mqc, uint8_t *cxstate, int lps) |
{ |
int d; |
if ((mqc->a < ff_mqc_qe[*cxstate]) ^ (!lps)) { |
if (lps) |
mqc->a = ff_mqc_qe[*cxstate]; |
d = *cxstate & 1; |
*cxstate = ff_mqc_nmps[*cxstate]; |
} else { |
if (lps) |
mqc->a = ff_mqc_qe[*cxstate]; |
d = 1 - (*cxstate & 1); |
*cxstate = ff_mqc_nlps[*cxstate]; |
} |
// do RENORMD: see ISO/IEC 15444-1:2002 §C.3.3 |
do { |
if (!(mqc->c & 0xff)) { |
mqc->c -= 0x100; |
bytein(mqc); |
} |
mqc->a += mqc->a; |
mqc->c += mqc->c; |
} while (!(mqc->a & 0x8000)); |
return d; |
} |
|
void ff_mqc_initdec(MqcState *mqc, uint8_t *bp) |
{ |
ff_mqc_init_contexts(mqc); |
mqc->bp = bp; |
mqc->c = (*mqc->bp ^ 0xff) << 16; |
bytein(mqc); |
mqc->c = mqc->c << 7; |
mqc->a = 0x8000; |
} |
|
int ff_mqc_decode(MqcState *mqc, uint8_t *cxstate) |
{ |
mqc->a -= ff_mqc_qe[*cxstate]; |
if ((mqc->c >> 16) < mqc->a) { |
if (mqc->a & 0x8000) |
return *cxstate & 1; |
else |
return exchange(mqc, cxstate, 0); |
} else { |
mqc->c -= mqc->a << 16; |
return exchange(mqc, cxstate, 1); |
} |
} |