xref: /third_party/ffmpeg/libavcodec/mqcenc.c (revision cabdff1a) 
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 <string.h>
29
30#include "libavutil/avassert.h"
31#include "mqc.h"
32
33static void byteout(MqcState *mqc)
34{
35retry:
36    if (*mqc->bp == 0xff){
37        mqc->bp++;
38        *mqc->bp = mqc->c >> 20;
39        mqc->c &= 0xfffff;
40        mqc->ct = 7;
41    } else if ((mqc->c & 0x8000000)){
42        (*mqc->bp)++;
43        mqc->c &= 0x7ffffff;
44        goto retry;
45    } else{
46        mqc->bp++;
47        *mqc->bp = mqc->c >> 19;
48        mqc->c &= 0x7ffff;
49        mqc->ct = 8;
50    }
51}
52
53static void renorme(MqcState *mqc)
54{
55    do{
56        mqc->a += mqc->a;
57        mqc->c += mqc->c;
58        if (!--mqc->ct)
59            byteout(mqc);
60    } while (!(mqc->a & 0x8000));
61}
62
63static void setbits(MqcState *mqc)
64{
65    int tmp = mqc->c + mqc->a;
66    mqc->c |= 0xffff;
67    if (mqc->c >= tmp)
68        mqc->c -= 0x8000;
69}
70
71void ff_mqc_initenc(MqcState *mqc, uint8_t *bp)
72{
73    ff_mqc_init_contexts(mqc);
74    mqc->a = 0x8000;
75    mqc->c = 0;
76    mqc->bp = bp-1;
77    mqc->bpstart = bp;
78    mqc->ct = 12 + (*mqc->bp == 0xff);
79}
80
81void ff_mqc_encode(MqcState *mqc, uint8_t *cxstate, int d)
82{
83    int qe;
84
85    qe = ff_mqc_qe[*cxstate];
86    mqc->a -= qe;
87    if ((*cxstate & 1) == d){
88        if (!(mqc->a & 0x8000)){
89            if (mqc->a < qe)
90                mqc->a = qe;
91            else
92                mqc->c += qe;
93            *cxstate = ff_mqc_nmps[*cxstate];
94            renorme(mqc);
95        } else
96            mqc->c += qe;
97    } else{
98        if (mqc->a < qe)
99            mqc->c += qe;
100        else
101            mqc->a = qe;
102        *cxstate = ff_mqc_nlps[*cxstate];
103        renorme(mqc);
104    }
105}
106
107static int mqc_flush(MqcState *mqc)
108{
109    setbits(mqc);
110    mqc->c = mqc->c << mqc->ct;
111    byteout(mqc);
112    mqc->c = mqc->c << mqc->ct;
113    byteout(mqc);
114    if (*mqc->bp != 0xff)
115        mqc->bp++;
116    return mqc->bp - mqc->bpstart;
117}
118
119int ff_mqc_flush_to(MqcState *mqc, uint8_t *dst, int *dst_len)
120{
121    MqcState mqc2 = *mqc;
122    mqc2.bpstart=
123    mqc2.bp = dst;
124    *mqc2.bp = *mqc->bp;
125    mqc_flush(&mqc2);
126    *dst_len = mqc2.bp - dst;
127    if (mqc->bp < mqc->bpstart) {
128        av_assert1(mqc->bpstart - mqc->bp == 1);
129        av_assert1(*dst_len > 0);
130        av_assert1(mqc->bp[0] == 0 && dst[0] == 0);
131        (*dst_len) --;
132        memmove(dst, dst+1, *dst_len);
133        return mqc->bp - mqc->bpstart + 1 + *dst_len;
134    }
135    return mqc->bp - mqc->bpstart + *dst_len;
136}
137