Line data Source code
1 : /*
2 : * MQ-coder decoder
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 decoder
24 : * @file
25 : * @author Kamil Nowosad
26 : */
27 :
28 : #include "mqc.h"
29 :
30 15972024 : static void bytein(MqcState *mqc)
31 : {
32 15972024 : if (*mqc->bp == 0xff) {
33 447940 : if (*(mqc->bp + 1) > 0x8f)
34 385409 : mqc->c++;
35 : else {
36 62531 : mqc->bp++;
37 62531 : mqc->c += 2 + 0xfe00 - (*mqc->bp << 9);
38 : }
39 : } else {
40 15524084 : mqc->bp++;
41 15524084 : mqc->c += 1 + 0xff00 - (*mqc->bp << 8);
42 : }
43 15972024 : }
44 :
45 88273842 : static int exchange(MqcState *mqc, uint8_t *cxstate, int lps)
46 : {
47 : int d;
48 88273842 : if ((mqc->a < ff_mqc_qe[*cxstate]) ^ (!lps)) {
49 46699411 : if (lps)
50 8992607 : mqc->a = ff_mqc_qe[*cxstate];
51 46699411 : d = *cxstate & 1;
52 46699411 : *cxstate = ff_mqc_nmps[*cxstate];
53 : } else {
54 41574431 : if (lps)
55 34304675 : mqc->a = ff_mqc_qe[*cxstate];
56 41574431 : d = 1 - (*cxstate & 1);
57 41574431 : *cxstate = ff_mqc_nlps[*cxstate];
58 : }
59 : // do RENORMD: see ISO/IEC 15444-1:2002 §C.3.3
60 : do {
61 124024020 : if (!(mqc->c & 0xff)) {
62 15609296 : mqc->c -= 0x100;
63 15609296 : bytein(mqc);
64 : }
65 124024020 : mqc->a += mqc->a;
66 124024020 : mqc->c += mqc->c;
67 124024020 : } while (!(mqc->a & 0x8000));
68 88273842 : return d;
69 : }
70 :
71 362728 : void ff_mqc_initdec(MqcState *mqc, uint8_t *bp, int raw, int reset)
72 : {
73 362728 : mqc->raw = raw;
74 362728 : if (reset)
75 362728 : ff_mqc_init_contexts(mqc);
76 362728 : mqc->bp = bp;
77 362728 : mqc->c = (*mqc->bp ^ 0xff) << 16;
78 362728 : bytein(mqc);
79 362728 : mqc->c = mqc->c << 7;
80 362728 : mqc->a = 0x8000;
81 362728 : }
82 :
83 0 : static int mqc_decode_bypass(MqcState *mqc) {
84 0 : int bit = !(mqc->c & 0x40000000);
85 0 : if (!(mqc->c & 0xff)) {
86 0 : mqc->c -= 0x100;
87 0 : bytein(mqc);
88 : }
89 0 : mqc->c += mqc->c;
90 0 : return bit;
91 : }
92 :
93 182845733 : int ff_mqc_decode(MqcState *mqc, uint8_t *cxstate)
94 : {
95 182845733 : if (mqc->raw)
96 0 : return mqc_decode_bypass(mqc);
97 182845733 : mqc->a -= ff_mqc_qe[*cxstate];
98 182845733 : if ((mqc->c >> 16) < mqc->a) {
99 139548451 : if (mqc->a & 0x8000)
100 94571891 : return *cxstate & 1;
101 : else
102 44976560 : return exchange(mqc, cxstate, 0);
103 : } else {
104 43297282 : mqc->c -= mqc->a << 16;
105 43297282 : return exchange(mqc, cxstate, 1);
106 : }
107 : }
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