mirror of https://github.com/FFmpeg/FFmpeg.git
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
93 lines
2.4 KiB
93 lines
2.4 KiB
/* |
|
* 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); |
|
} |
|
}
|
|
|