| 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 = CODEC_CAP_DR1, |
| 228 | }; |