summaryrefslogtreecommitdiffstats
path: root/libavcodec/mss1.c
blob: 6679a1c1f7fe93233bcd0a40a718e2ac48f103e7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
/*
 * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder
 * Copyright (c) 2012 Konstantin Shishkov
 *
 * 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
 */

/**
 * @file
 * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder
 */

#include "avcodec.h"
#include "internal.h"
#include "mss12.h"

typedef struct MSS1Context {
    MSS12Context   ctx;
    AVFrame       *pic;
    SliceContext   sc;
} MSS1Context;

static void arith1_normalise(ArithCoder *c)
{
    for (;;) {
        if (c->high >= 0x8000) {
            if (c->low < 0x8000) {
                if (c->low >= 0x4000 && c->high < 0xC000) {
                    c->value -= 0x4000;
                    c->low   -= 0x4000;
                    c->high  -= 0x4000;
                } else {
                    return;
                }
            } else {
                c->value -= 0x8000;
                c->low   -= 0x8000;
                c->high  -= 0x8000;
            }
        }
        c->value <<= 1;
        c->low   <<= 1;
        c->high  <<= 1;
        c->high   |= 1;
        c->value  |= get_bits1(c->gbc.gb);
    }
}

ARITH_GET_BIT(1)

static int arith_get_bits(ArithCoder *c, int bits)
{
    int range = c->high - c->low + 1;
    int val   = (((c->value - c->low + 1) << bits) - 1) / range;
    int prob  = range * val;

    c->high   = ((prob + range) >> bits) + c->low - 1;
    c->low   += prob >> bits;

    arith1_normalise(c);

    return val;
}

static int arith_get_number(ArithCoder *c, int mod_val)
{
    int range = c->high - c->low + 1;
    int val   = ((c->value - c->low + 1) * mod_val - 1) / range;
    int prob  = range * val;

    c->high   = (prob + range) / mod_val + c->low - 1;
    c->low   += prob / mod_val;

    arith1_normalise(c);

    return val;
}

static int arith1_get_prob(ArithCoder *c, int16_t *probs)
{
    int range = c->high - c->low + 1;
    int val   = ((c->value - c->low + 1) * probs[0] - 1) / range;
    int sym   = 1;

    while (probs[sym] > val)
        sym++;

    c->high = range * probs[sym - 1] / probs[0] + c->low - 1;
    c->low += range * probs[sym]     / probs[0];

    return sym;
}

ARITH_GET_MODEL_SYM(1)

static void arith_init(ArithCoder *c, GetBitContext *gb)
{
    c->low           = 0;
    c->high          = 0xFFFF;
    c->value         = get_bits(gb, 16);
    c->gbc.gb        = gb;
    c->get_model_sym = arith1_get_model_sym;
    c->get_number    = arith_get_number;
}

static int decode_pal(MSS12Context *ctx, ArithCoder *acoder)
{
    int i, ncol, r, g, b;
    uint32_t *pal = ctx->pal + 256 - ctx->free_colours;

    if (!ctx->free_colours)
        return 0;

    ncol = arith_get_number(acoder, ctx->free_colours + 1);
    for (i = 0; i < ncol; i++) {
        r = arith_get_bits(acoder, 8);
        g = arith_get_bits(acoder, 8);
        b = arith_get_bits(acoder, 8);
        *pal++ = (r << 16) | (g << 8) | b;
    }

    return !!ncol;
}

static int mss1_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
                             AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size = avpkt->size;
    MSS1Context *ctx = avctx->priv_data;
    MSS12Context *c = &ctx->ctx;
    GetBitContext gb;
    ArithCoder acoder;
    int pal_changed = 0;
    int ret;

    init_get_bits(&gb, buf, buf_size * 8);
    arith_init(&acoder, &gb);

    if ((ret = ff_reget_buffer(avctx, ctx->pic)) < 0) {
        av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n");
        return ret;
    }

    c->pal_pic    =  ctx->pic->data[0] + ctx->pic->linesize[0] * (avctx->height - 1);
    c->pal_stride = -ctx->pic->linesize[0];
    c->keyframe   = !arith1_get_bit(&acoder);
    if (c->keyframe) {
        c->corrupted = 0;
        ff_mss12_slicecontext_reset(&ctx->sc);
        pal_changed        = decode_pal(c, &acoder);
        ctx->pic->key_frame = 1;
        ctx->pic->pict_type = AV_PICTURE_TYPE_I;
    } else {
        if (c->corrupted)
            return AVERROR_INVALIDDATA;
        ctx->pic->key_frame = 0;
        ctx->pic->pict_type = AV_PICTURE_TYPE_P;
    }
    c->corrupted = ff_mss12_decode_rect(&ctx->sc, &acoder, 0, 0,
                                        avctx->width, avctx->height);
    if (c->corrupted)
        return AVERROR_INVALIDDATA;
    memcpy(ctx->pic->data[1], c->pal, AVPALETTE_SIZE);
    ctx->pic->palette_has_changed = pal_changed;

    if ((ret = av_frame_ref(data, ctx->pic)) < 0)
        return ret;

    *got_frame      = 1;

    /* always report that the buffer was completely consumed */
    return buf_size;
}

static av_cold int mss1_decode_init(AVCodecContext *avctx)
{
    MSS1Context * const c = avctx->priv_data;
    int ret;

    c->ctx.avctx       = avctx;

    c->pic = av_frame_alloc();
    if (!c->pic)
        return AVERROR(ENOMEM);

    ret = ff_mss12_decode_init(&c->ctx, 0, &c->sc, NULL);

    avctx->pix_fmt = AV_PIX_FMT_PAL8;

    return ret;
}

static av_cold int mss1_decode_end(AVCodecContext *avctx)
{
    MSS1Context * const ctx = avctx->priv_data;

    av_frame_free(&ctx->pic);
    ff_mss12_decode_end(&ctx->ctx);

    return 0;
}

AVCodec ff_mss1_decoder = {
    .name           = "mss1",
    .long_name      = NULL_IF_CONFIG_SMALL("MS Screen 1"),
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = AV_CODEC_ID_MSS1,
    .priv_data_size = sizeof(MSS1Context),
    .init           = mss1_decode_init,
    .close          = mss1_decode_end,
    .decode         = mss1_decode_frame,
    .capabilities   = AV_CODEC_CAP_DR1,
};
OpenPOWER on IntegriCloud