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1 | /* |
2 | * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder | |
3 | * Copyright (c) 2012 Konstantin Shishkov | |
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 | * @file | |
24 | * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder | |
25 | */ | |
26 | ||
27 | #include "avcodec.h" | |
28 | #include "internal.h" | |
29 | #include "mss12.h" | |
30 | ||
31 | typedef struct MSS1Context { | |
32 | MSS12Context ctx; | |
33 | AVFrame *pic; | |
34 | SliceContext sc; | |
35 | } MSS1Context; | |
36 | ||
37 | static void arith_normalise(ArithCoder *c) | |
38 | { | |
39 | for (;;) { | |
40 | if (c->high >= 0x8000) { | |
41 | if (c->low < 0x8000) { | |
42 | if (c->low >= 0x4000 && c->high < 0xC000) { | |
43 | c->value -= 0x4000; | |
44 | c->low -= 0x4000; | |
45 | c->high -= 0x4000; | |
46 | } else { | |
47 | return; | |
48 | } | |
49 | } else { | |
50 | c->value -= 0x8000; | |
51 | c->low -= 0x8000; | |
52 | c->high -= 0x8000; | |
53 | } | |
54 | } | |
55 | c->value <<= 1; | |
56 | c->low <<= 1; | |
57 | c->high <<= 1; | |
58 | c->high |= 1; | |
59 | c->value |= get_bits1(c->gbc.gb); | |
60 | } | |
61 | } | |
62 | ||
63 | ARITH_GET_BIT(arith) | |
64 | ||
65 | static int arith_get_bits(ArithCoder *c, int bits) | |
66 | { | |
67 | int range = c->high - c->low + 1; | |
68 | int val = (((c->value - c->low + 1) << bits) - 1) / range; | |
69 | int prob = range * val; | |
70 | ||
71 | c->high = ((prob + range) >> bits) + c->low - 1; | |
72 | c->low += prob >> bits; | |
73 | ||
74 | arith_normalise(c); | |
75 | ||
76 | return val; | |
77 | } | |
78 | ||
79 | static int arith_get_number(ArithCoder *c, int mod_val) | |
80 | { | |
81 | int range = c->high - c->low + 1; | |
82 | int val = ((c->value - c->low + 1) * mod_val - 1) / range; | |
83 | int prob = range * val; | |
84 | ||
85 | c->high = (prob + range) / mod_val + c->low - 1; | |
86 | c->low += prob / mod_val; | |
87 | ||
88 | arith_normalise(c); | |
89 | ||
90 | return val; | |
91 | } | |
92 | ||
93 | static int arith_get_prob(ArithCoder *c, int16_t *probs) | |
94 | { | |
95 | int range = c->high - c->low + 1; | |
96 | int val = ((c->value - c->low + 1) * probs[0] - 1) / range; | |
97 | int sym = 1; | |
98 | ||
99 | while (probs[sym] > val) | |
100 | sym++; | |
101 | ||
102 | c->high = range * probs[sym - 1] / probs[0] + c->low - 1; | |
103 | c->low += range * probs[sym] / probs[0]; | |
104 | ||
105 | return sym; | |
106 | } | |
107 | ||
108 | ARITH_GET_MODEL_SYM(arith) | |
109 | ||
110 | static void arith_init(ArithCoder *c, GetBitContext *gb) | |
111 | { | |
112 | c->low = 0; | |
113 | c->high = 0xFFFF; | |
114 | c->value = get_bits(gb, 16); | |
115 | c->gbc.gb = gb; | |
116 | c->get_model_sym = arith_get_model_sym; | |
117 | c->get_number = arith_get_number; | |
118 | } | |
119 | ||
120 | static int decode_pal(MSS12Context *ctx, ArithCoder *acoder) | |
121 | { | |
122 | int i, ncol, r, g, b; | |
123 | uint32_t *pal = ctx->pal + 256 - ctx->free_colours; | |
124 | ||
125 | if (!ctx->free_colours) | |
126 | return 0; | |
127 | ||
128 | ncol = arith_get_number(acoder, ctx->free_colours + 1); | |
129 | for (i = 0; i < ncol; i++) { | |
130 | r = arith_get_bits(acoder, 8); | |
131 | g = arith_get_bits(acoder, 8); | |
132 | b = arith_get_bits(acoder, 8); | |
133 | *pal++ = (0xFFU << 24) | (r << 16) | (g << 8) | b; | |
134 | } | |
135 | ||
136 | return !!ncol; | |
137 | } | |
138 | ||
139 | static int mss1_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, | |
140 | AVPacket *avpkt) | |
141 | { | |
142 | MSS1Context *ctx = avctx->priv_data; | |
143 | MSS12Context *c = &ctx->ctx; | |
144 | GetBitContext gb; | |
145 | ArithCoder acoder; | |
146 | int pal_changed = 0; | |
147 | int ret; | |
148 | ||
149 | if ((ret = init_get_bits8(&gb, avpkt->data, avpkt->size)) < 0) | |
150 | return ret; | |
151 | ||
152 | arith_init(&acoder, &gb); | |
153 | ||
154 | if ((ret = ff_reget_buffer(avctx, ctx->pic)) < 0) | |
155 | return ret; | |
156 | ||
157 | c->pal_pic = ctx->pic->data[0] + ctx->pic->linesize[0] * (avctx->height - 1); | |
158 | c->pal_stride = -ctx->pic->linesize[0]; | |
159 | c->keyframe = !arith_get_bit(&acoder); | |
160 | if (c->keyframe) { | |
161 | c->corrupted = 0; | |
162 | ff_mss12_slicecontext_reset(&ctx->sc); | |
163 | pal_changed = decode_pal(c, &acoder); | |
164 | ctx->pic->key_frame = 1; | |
165 | ctx->pic->pict_type = AV_PICTURE_TYPE_I; | |
166 | } else { | |
167 | if (c->corrupted) | |
168 | return AVERROR_INVALIDDATA; | |
169 | ctx->pic->key_frame = 0; | |
170 | ctx->pic->pict_type = AV_PICTURE_TYPE_P; | |
171 | } | |
172 | c->corrupted = ff_mss12_decode_rect(&ctx->sc, &acoder, 0, 0, | |
173 | avctx->width, avctx->height); | |
174 | if (c->corrupted) | |
175 | return AVERROR_INVALIDDATA; | |
176 | memcpy(ctx->pic->data[1], c->pal, AVPALETTE_SIZE); | |
177 | ctx->pic->palette_has_changed = pal_changed; | |
178 | ||
179 | if ((ret = av_frame_ref(data, ctx->pic)) < 0) | |
180 | return ret; | |
181 | ||
182 | *got_frame = 1; | |
183 | ||
184 | /* always report that the buffer was completely consumed */ | |
185 | return avpkt->size; | |
186 | } | |
187 | ||
188 | static av_cold int mss1_decode_init(AVCodecContext *avctx) | |
189 | { | |
190 | MSS1Context * const c = avctx->priv_data; | |
191 | int ret; | |
192 | ||
193 | c->ctx.avctx = avctx; | |
194 | ||
195 | c->pic = av_frame_alloc(); | |
196 | if (!c->pic) | |
197 | return AVERROR(ENOMEM); | |
198 | ||
199 | ret = ff_mss12_decode_init(&c->ctx, 0, &c->sc, NULL); | |
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200 | if (ret < 0) |
201 | av_frame_free(&c->pic); | |
2ba45a60 DM |
202 | |
203 | avctx->pix_fmt = AV_PIX_FMT_PAL8; | |
204 | ||
205 | return ret; | |
206 | } | |
207 | ||
208 | static av_cold int mss1_decode_end(AVCodecContext *avctx) | |
209 | { | |
210 | MSS1Context * const ctx = avctx->priv_data; | |
211 | ||
212 | av_frame_free(&ctx->pic); | |
213 | ff_mss12_decode_end(&ctx->ctx); | |
214 | ||
215 | return 0; | |
216 | } | |
217 | ||
218 | AVCodec ff_mss1_decoder = { | |
219 | .name = "mss1", | |
220 | .long_name = NULL_IF_CONFIG_SMALL("MS Screen 1"), | |
221 | .type = AVMEDIA_TYPE_VIDEO, | |
222 | .id = AV_CODEC_ID_MSS1, | |
223 | .priv_data_size = sizeof(MSS1Context), | |
224 | .init = mss1_decode_init, | |
225 | .close = mss1_decode_end, | |
226 | .decode = mss1_decode_frame, | |
227 | .capabilities = CODEC_CAP_DR1, | |
228 | }; |