mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-12-28 20:53:54 +02:00
c81a706381
Based on the 2007 GSoC project from Kamil Nowosad <k.nowosad@students.mimuw.edu.pl> Updated to current programming standards, style and many more small fixes by Diego Biurrun <diego@biurrun.de>. Signed-off-by: Diego Biurrun <diego@biurrun.de>
94 lines
2.4 KiB
C
94 lines
2.4 KiB
C
/*
|
|
* MQ-coder decoder
|
|
* Copyright (c) 2007 Kamil Nowosad
|
|
*
|
|
* This file is part of Libav.
|
|
*
|
|
* Libav 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.
|
|
*
|
|
* Libav 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 Libav; 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);
|
|
}
|
|
}
|