blob: a579d9d9a44999248c162e9516c10f8e4a0de139
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); |
200 | if (ret < 0) |
201 | av_frame_free(&c->pic); |
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 = AV_CODEC_CAP_DR1, |
228 | }; |
229 |