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mqcenc.c
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1 /*
2  * MQ-coder encoder
3  * Copyright (c) 2007 Kamil Nowosad
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 /**
23  * MQ-coder encoder
24  * @file
25  * @author Kamil Nowosad
26  */
27 
28 #include "mqc.h"
29 
30 static void byteout(MqcState *mqc)
31 {
32 retry:
33  if (*mqc->bp == 0xff){
34  mqc->bp++;
35  *mqc->bp = mqc->c >> 20;
36  mqc->c &= 0xfffff;
37  mqc->ct = 7;
38  } else if ((mqc->c & 0x8000000)){
39  (*mqc->bp)++;
40  mqc->c &= 0x7ffffff;
41  goto retry;
42  } else{
43  mqc->bp++;
44  *mqc->bp = mqc->c >> 19;
45  mqc->c &= 0x7ffff;
46  mqc->ct = 8;
47  }
48 }
49 
50 static void renorme(MqcState *mqc)
51 {
52  do{
53  mqc->a += mqc->a;
54  mqc->c += mqc->c;
55  if (!--mqc->ct)
56  byteout(mqc);
57  } while (!(mqc->a & 0x8000));
58 }
59 
60 static void setbits(MqcState *mqc)
61 {
62  int tmp = mqc->c + mqc->a;
63  mqc->c |= 0xffff;
64  if (mqc->c >= tmp)
65  mqc->c -= 0x8000;
66 }
67 
69 {
71  mqc->a = 0x8000;
72  mqc->c = 0;
73  mqc->bp = bp-1;
74  mqc->bpstart = bp;
75  mqc->ct = 12 + (*mqc->bp == 0xff);
76 }
77 
78 void ff_mqc_encode(MqcState *mqc, uint8_t *cxstate, int d)
79 {
80  int qe;
81 
82  qe = ff_mqc_qe[*cxstate];
83  mqc->a -= qe;
84  if ((*cxstate & 1) == d){
85  if (!(mqc->a & 0x8000)){
86  if (mqc->a < qe)
87  mqc->a = qe;
88  else
89  mqc->c += qe;
90  *cxstate = ff_mqc_nmps[*cxstate];
91  renorme(mqc);
92  } else
93  mqc->c += qe;
94  } else{
95  if (mqc->a < qe)
96  mqc->c += qe;
97  else
98  mqc->a = qe;
99  *cxstate = ff_mqc_nlps[*cxstate];
100  renorme(mqc);
101  }
102 }
103 
105 {
106  return mqc->bp - mqc->bpstart;
107 }
108 
110 {
111  setbits(mqc);
112  mqc->c = mqc->c << mqc->ct;
113  byteout(mqc);
114  mqc->c = mqc->c << mqc->ct;
115  byteout(mqc);
116  if (*mqc->bp != 0xff)
117  mqc->bp++;
118  return mqc->bp - mqc->bpstart;
119 }