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4349 | Serge | 1 | /* |
2 | * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder |
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3 | * Copyright (c) 2012 Konstantin Shishkov |
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4 | * |
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5 | * This file is part of FFmpeg. |
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6 | * |
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7 | * FFmpeg is free software; you can redistribute it and/or |
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8 | * modify it under the terms of the GNU Lesser General Public |
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9 | * License as published by the Free Software Foundation; either |
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10 | * version 2.1 of the License, or (at your option) any later version. |
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11 | * |
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12 | * FFmpeg is distributed in the hope that it will be useful, |
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13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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15 | * Lesser General Public License for more details. |
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16 | * |
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17 | * You should have received a copy of the GNU Lesser General Public |
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18 | * License along with FFmpeg; if not, write to the Free Software |
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19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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20 | */ |
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21 | |||
22 | /** |
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23 | * @file |
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24 | * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder |
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25 | */ |
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26 | |||
27 | #include "avcodec.h" |
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28 | #include "internal.h" |
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29 | #include "mss12.h" |
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30 | |||
31 | typedef struct MSS1Context { |
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32 | MSS12Context ctx; |
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33 | AVFrame pic; |
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34 | SliceContext sc; |
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35 | } MSS1Context; |
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36 | |||
37 | static void arith_normalise(ArithCoder *c) |
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38 | { |
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39 | for (;;) { |
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40 | if (c->high >= 0x8000) { |
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41 | if (c->low < 0x8000) { |
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42 | if (c->low >= 0x4000 && c->high < 0xC000) { |
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43 | c->value -= 0x4000; |
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44 | c->low -= 0x4000; |
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45 | c->high -= 0x4000; |
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46 | } else { |
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47 | return; |
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48 | } |
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49 | } else { |
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50 | c->value -= 0x8000; |
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51 | c->low -= 0x8000; |
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52 | c->high -= 0x8000; |
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53 | } |
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54 | } |
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55 | c->value <<= 1; |
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56 | c->low <<= 1; |
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57 | c->high <<= 1; |
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58 | c->high |= 1; |
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59 | c->value |= get_bits1(c->gbc.gb); |
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60 | } |
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61 | } |
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62 | |||
63 | ARITH_GET_BIT() |
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64 | |||
65 | static int arith_get_bits(ArithCoder *c, int bits) |
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66 | { |
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67 | int range = c->high - c->low + 1; |
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68 | int val = (((c->value - c->low + 1) << bits) - 1) / range; |
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69 | int prob = range * val; |
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70 | |||
71 | c->high = ((prob + range) >> bits) + c->low - 1; |
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72 | c->low += prob >> bits; |
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73 | |||
74 | arith_normalise(c); |
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75 | |||
76 | return val; |
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77 | } |
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78 | |||
79 | static int arith_get_number(ArithCoder *c, int mod_val) |
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80 | { |
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81 | int range = c->high - c->low + 1; |
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82 | int val = ((c->value - c->low + 1) * mod_val - 1) / range; |
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83 | int prob = range * val; |
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84 | |||
85 | c->high = (prob + range) / mod_val + c->low - 1; |
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86 | c->low += prob / mod_val; |
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87 | |||
88 | arith_normalise(c); |
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89 | |||
90 | return val; |
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91 | } |
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92 | |||
93 | static int arith_get_prob(ArithCoder *c, int16_t *probs) |
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94 | { |
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95 | int range = c->high - c->low + 1; |
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96 | int val = ((c->value - c->low + 1) * probs[0] - 1) / range; |
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97 | int sym = 1; |
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98 | |||
99 | while (probs[sym] > val) |
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100 | sym++; |
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101 | |||
102 | c->high = range * probs[sym - 1] / probs[0] + c->low - 1; |
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103 | c->low += range * probs[sym] / probs[0]; |
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104 | |||
105 | return sym; |
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106 | } |
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107 | |||
108 | ARITH_GET_MODEL_SYM() |
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109 | |||
110 | static void arith_init(ArithCoder *c, GetBitContext *gb) |
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111 | { |
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112 | c->low = 0; |
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113 | c->high = 0xFFFF; |
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114 | c->value = get_bits(gb, 16); |
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115 | c->gbc.gb = gb; |
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116 | c->get_model_sym = arith_get_model_sym; |
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117 | c->get_number = arith_get_number; |
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118 | } |
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119 | |||
120 | static int decode_pal(MSS12Context *ctx, ArithCoder *acoder) |
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121 | { |
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122 | int i, ncol, r, g, b; |
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123 | uint32_t *pal = ctx->pal + 256 - ctx->free_colours; |
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124 | |||
125 | if (!ctx->free_colours) |
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126 | return 0; |
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127 | |||
128 | ncol = arith_get_number(acoder, ctx->free_colours + 1); |
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129 | for (i = 0; i < ncol; i++) { |
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130 | r = arith_get_bits(acoder, 8); |
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131 | g = arith_get_bits(acoder, 8); |
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132 | b = arith_get_bits(acoder, 8); |
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133 | *pal++ = (0xFFU << 24) | (r << 16) | (g << 8) | b; |
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134 | } |
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135 | |||
136 | return !!ncol; |
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137 | } |
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138 | |||
139 | static int mss1_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, |
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140 | AVPacket *avpkt) |
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141 | { |
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142 | const uint8_t *buf = avpkt->data; |
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143 | int buf_size = avpkt->size; |
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144 | MSS1Context *ctx = avctx->priv_data; |
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145 | MSS12Context *c = &ctx->ctx; |
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146 | GetBitContext gb; |
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147 | ArithCoder acoder; |
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148 | int pal_changed = 0; |
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149 | int ret; |
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150 | |||
151 | init_get_bits(&gb, buf, buf_size * 8); |
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152 | arith_init(&acoder, &gb); |
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153 | |||
154 | if ((ret = ff_reget_buffer(avctx, &ctx->pic)) < 0) |
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155 | return ret; |
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156 | |||
157 | c->pal_pic = ctx->pic.data[0] + ctx->pic.linesize[0] * (avctx->height - 1); |
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158 | c->pal_stride = -ctx->pic.linesize[0]; |
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159 | c->keyframe = !arith_get_bit(&acoder); |
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160 | if (c->keyframe) { |
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161 | c->corrupted = 0; |
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162 | ff_mss12_slicecontext_reset(&ctx->sc); |
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163 | pal_changed = decode_pal(c, &acoder); |
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164 | ctx->pic.key_frame = 1; |
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165 | ctx->pic.pict_type = AV_PICTURE_TYPE_I; |
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166 | } else { |
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167 | if (c->corrupted) |
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168 | return AVERROR_INVALIDDATA; |
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169 | ctx->pic.key_frame = 0; |
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170 | ctx->pic.pict_type = AV_PICTURE_TYPE_P; |
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171 | } |
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172 | c->corrupted = ff_mss12_decode_rect(&ctx->sc, &acoder, 0, 0, |
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173 | avctx->width, avctx->height); |
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174 | if (c->corrupted) |
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175 | return AVERROR_INVALIDDATA; |
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176 | memcpy(ctx->pic.data[1], c->pal, AVPALETTE_SIZE); |
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177 | ctx->pic.palette_has_changed = pal_changed; |
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178 | |||
179 | if ((ret = av_frame_ref(data, &ctx->pic)) < 0) |
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180 | return ret; |
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181 | |||
182 | *got_frame = 1; |
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183 | |||
184 | /* always report that the buffer was completely consumed */ |
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185 | return buf_size; |
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186 | } |
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187 | |||
188 | static av_cold int mss1_decode_init(AVCodecContext *avctx) |
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189 | { |
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190 | MSS1Context * const c = avctx->priv_data; |
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191 | int ret; |
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192 | |||
193 | c->ctx.avctx = avctx; |
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194 | |||
195 | avcodec_get_frame_defaults(&c->pic); |
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196 | |||
197 | ret = ff_mss12_decode_init(&c->ctx, 0, &c->sc, NULL); |
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198 | |||
199 | avctx->pix_fmt = AV_PIX_FMT_PAL8; |
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200 | |||
201 | return ret; |
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202 | } |
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203 | |||
204 | static av_cold int mss1_decode_end(AVCodecContext *avctx) |
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205 | { |
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206 | MSS1Context * const ctx = avctx->priv_data; |
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207 | |||
208 | av_frame_unref(&ctx->pic); |
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209 | ff_mss12_decode_end(&ctx->ctx); |
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210 | |||
211 | return 0; |
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212 | } |
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213 | |||
214 | AVCodec ff_mss1_decoder = { |
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215 | .name = "mss1", |
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216 | .long_name = NULL_IF_CONFIG_SMALL("MS Screen 1"), |
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217 | .type = AVMEDIA_TYPE_VIDEO, |
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218 | .id = AV_CODEC_ID_MSS1, |
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219 | .priv_data_size = sizeof(MSS1Context), |
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220 | .init = mss1_decode_init, |
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221 | .close = mss1_decode_end, |
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222 | .decode = mss1_decode_frame, |
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223 | .capabilities = CODEC_CAP_DR1, |
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224 | };>>><>><>><>>><>=><=>=><=>=><=>>> |