| 1 | /* |
| 2 | * Discworld II BMV video decoder |
| 3 | * Copyright (c) 2011 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 | #include "libavutil/avassert.h" |
| 23 | #include "libavutil/common.h" |
| 24 | |
| 25 | #include "avcodec.h" |
| 26 | #include "bytestream.h" |
| 27 | #include "internal.h" |
| 28 | |
| 29 | enum BMVFlags{ |
| 30 | BMV_NOP = 0, |
| 31 | BMV_END, |
| 32 | BMV_DELTA, |
| 33 | BMV_INTRA, |
| 34 | |
| 35 | BMV_SCROLL = 0x04, |
| 36 | BMV_PALETTE = 0x08, |
| 37 | BMV_COMMAND = 0x10, |
| 38 | BMV_AUDIO = 0x20, |
| 39 | BMV_EXT = 0x40, |
| 40 | BMV_PRINT = 0x80 |
| 41 | }; |
| 42 | |
| 43 | #define SCREEN_WIDE 640 |
| 44 | #define SCREEN_HIGH 429 |
| 45 | |
| 46 | typedef struct BMVDecContext { |
| 47 | AVCodecContext *avctx; |
| 48 | |
| 49 | uint8_t *frame, frame_base[SCREEN_WIDE * (SCREEN_HIGH + 1)]; |
| 50 | uint32_t pal[256]; |
| 51 | const uint8_t *stream; |
| 52 | } BMVDecContext; |
| 53 | |
| 54 | #define NEXT_BYTE(v) v = forward ? v + 1 : v - 1; |
| 55 | |
| 56 | static int decode_bmv_frame(const uint8_t *source, int src_len, uint8_t *frame, int frame_off) |
| 57 | { |
| 58 | unsigned val, saved_val = 0; |
| 59 | int tmplen = src_len; |
| 60 | const uint8_t *src, *source_end = source + src_len; |
| 61 | uint8_t *frame_end = frame + SCREEN_WIDE * SCREEN_HIGH; |
| 62 | uint8_t *dst, *dst_end; |
| 63 | int len, mask; |
| 64 | int forward = (frame_off <= -SCREEN_WIDE) || (frame_off >= 0); |
| 65 | int read_two_nibbles, flag; |
| 66 | int advance_mode; |
| 67 | int mode = 0; |
| 68 | int i; |
| 69 | |
| 70 | if (src_len <= 0) |
| 71 | return AVERROR_INVALIDDATA; |
| 72 | |
| 73 | if (forward) { |
| 74 | src = source; |
| 75 | dst = frame; |
| 76 | dst_end = frame_end; |
| 77 | } else { |
| 78 | src = source + src_len - 1; |
| 79 | dst = frame_end - 1; |
| 80 | dst_end = frame - 1; |
| 81 | } |
| 82 | for (;;) { |
| 83 | int shift = 0; |
| 84 | flag = 0; |
| 85 | |
| 86 | /* The mode/len decoding is a bit strange: |
| 87 | * values are coded as variable-length codes with nibble units, |
| 88 | * code end is signalled by two top bits in the nibble being nonzero. |
| 89 | * And since data is bytepacked and we read two nibbles at a time, |
| 90 | * we may get a nibble belonging to the next code. |
| 91 | * Hence this convoluted loop. |
| 92 | */ |
| 93 | if (!mode || (tmplen == 4)) { |
| 94 | if (src < source || src >= source_end) |
| 95 | return AVERROR_INVALIDDATA; |
| 96 | val = *src; |
| 97 | read_two_nibbles = 1; |
| 98 | } else { |
| 99 | val = saved_val; |
| 100 | read_two_nibbles = 0; |
| 101 | } |
| 102 | if (!(val & 0xC)) { |
| 103 | for (;;) { |
| 104 | if(shift>22) |
| 105 | return -1; |
| 106 | if (!read_two_nibbles) { |
| 107 | if (src < source || src >= source_end) |
| 108 | return AVERROR_INVALIDDATA; |
| 109 | shift += 2; |
| 110 | val |= *src << shift; |
| 111 | if (*src & 0xC) |
| 112 | break; |
| 113 | } |
| 114 | // two upper bits of the nibble is zero, |
| 115 | // so shift top nibble value down into their place |
| 116 | read_two_nibbles = 0; |
| 117 | shift += 2; |
| 118 | mask = (1 << shift) - 1; |
| 119 | val = ((val >> 2) & ~mask) | (val & mask); |
| 120 | NEXT_BYTE(src); |
| 121 | if ((val & (0xC << shift))) { |
| 122 | flag = 1; |
| 123 | break; |
| 124 | } |
| 125 | } |
| 126 | } else if (mode) { |
| 127 | flag = tmplen != 4; |
| 128 | } |
| 129 | if (flag) { |
| 130 | tmplen = 4; |
| 131 | } else { |
| 132 | saved_val = val >> (4 + shift); |
| 133 | tmplen = 0; |
| 134 | val &= (1 << (shift + 4)) - 1; |
| 135 | NEXT_BYTE(src); |
| 136 | } |
| 137 | advance_mode = val & 1; |
| 138 | len = (val >> 1) - 1; |
| 139 | av_assert0(len>0); |
| 140 | mode += 1 + advance_mode; |
| 141 | if (mode >= 4) |
| 142 | mode -= 3; |
| 143 | if (len <= 0 || FFABS(dst_end - dst) < len) |
| 144 | return AVERROR_INVALIDDATA; |
| 145 | switch (mode) { |
| 146 | case 1: |
| 147 | if (forward) { |
| 148 | if (dst - frame + SCREEN_WIDE < frame_off || |
| 149 | dst - frame + SCREEN_WIDE + frame_off < 0 || |
| 150 | frame_end - dst < frame_off + len || |
| 151 | frame_end - dst < len) |
| 152 | return AVERROR_INVALIDDATA; |
| 153 | for (i = 0; i < len; i++) |
| 154 | dst[i] = dst[frame_off + i]; |
| 155 | dst += len; |
| 156 | } else { |
| 157 | dst -= len; |
| 158 | if (dst - frame + SCREEN_WIDE < frame_off || |
| 159 | dst - frame + SCREEN_WIDE + frame_off < 0 || |
| 160 | frame_end - dst < frame_off + len || |
| 161 | frame_end - dst < len) |
| 162 | return AVERROR_INVALIDDATA; |
| 163 | for (i = len - 1; i >= 0; i--) |
| 164 | dst[i] = dst[frame_off + i]; |
| 165 | } |
| 166 | break; |
| 167 | case 2: |
| 168 | if (forward) { |
| 169 | if (source + src_len - src < len) |
| 170 | return AVERROR_INVALIDDATA; |
| 171 | memcpy(dst, src, len); |
| 172 | dst += len; |
| 173 | src += len; |
| 174 | } else { |
| 175 | if (src - source < len) |
| 176 | return AVERROR_INVALIDDATA; |
| 177 | dst -= len; |
| 178 | src -= len; |
| 179 | memcpy(dst, src, len); |
| 180 | } |
| 181 | break; |
| 182 | case 3: |
| 183 | val = forward ? dst[-1] : dst[1]; |
| 184 | if (forward) { |
| 185 | memset(dst, val, len); |
| 186 | dst += len; |
| 187 | } else { |
| 188 | dst -= len; |
| 189 | memset(dst, val, len); |
| 190 | } |
| 191 | break; |
| 192 | } |
| 193 | if (dst == dst_end) |
| 194 | return 0; |
| 195 | } |
| 196 | return 0; |
| 197 | } |
| 198 | |
| 199 | static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame, |
| 200 | AVPacket *pkt) |
| 201 | { |
| 202 | BMVDecContext * const c = avctx->priv_data; |
| 203 | AVFrame *frame = data; |
| 204 | int type, scr_off; |
| 205 | int i, ret; |
| 206 | uint8_t *srcptr, *outptr; |
| 207 | |
| 208 | c->stream = pkt->data; |
| 209 | type = bytestream_get_byte(&c->stream); |
| 210 | if (type & BMV_AUDIO) { |
| 211 | int blobs = bytestream_get_byte(&c->stream); |
| 212 | if (pkt->size < blobs * 65 + 2) { |
| 213 | av_log(avctx, AV_LOG_ERROR, "Audio data doesn't fit in frame\n"); |
| 214 | return AVERROR_INVALIDDATA; |
| 215 | } |
| 216 | c->stream += blobs * 65; |
| 217 | } |
| 218 | if (type & BMV_COMMAND) { |
| 219 | int command_size = (type & BMV_PRINT) ? 8 : 10; |
| 220 | if (c->stream - pkt->data + command_size > pkt->size) { |
| 221 | av_log(avctx, AV_LOG_ERROR, "Command data doesn't fit in frame\n"); |
| 222 | return AVERROR_INVALIDDATA; |
| 223 | } |
| 224 | c->stream += command_size; |
| 225 | } |
| 226 | if (type & BMV_PALETTE) { |
| 227 | if (c->stream - pkt->data > pkt->size - 768) { |
| 228 | av_log(avctx, AV_LOG_ERROR, "Palette data doesn't fit in frame\n"); |
| 229 | return AVERROR_INVALIDDATA; |
| 230 | } |
| 231 | for (i = 0; i < 256; i++) |
| 232 | c->pal[i] = 0xFFU << 24 | bytestream_get_be24(&c->stream); |
| 233 | } |
| 234 | if (type & BMV_SCROLL) { |
| 235 | if (c->stream - pkt->data > pkt->size - 2) { |
| 236 | av_log(avctx, AV_LOG_ERROR, "Screen offset data doesn't fit in frame\n"); |
| 237 | return AVERROR_INVALIDDATA; |
| 238 | } |
| 239 | scr_off = (int16_t)bytestream_get_le16(&c->stream); |
| 240 | } else if ((type & BMV_INTRA) == BMV_INTRA) { |
| 241 | scr_off = -640; |
| 242 | } else { |
| 243 | scr_off = 0; |
| 244 | } |
| 245 | |
| 246 | if ((ret = ff_get_buffer(avctx, frame, 0)) < 0) |
| 247 | return ret; |
| 248 | |
| 249 | if (decode_bmv_frame(c->stream, pkt->size - (c->stream - pkt->data), c->frame, scr_off)) { |
| 250 | av_log(avctx, AV_LOG_ERROR, "Error decoding frame data\n"); |
| 251 | return AVERROR_INVALIDDATA; |
| 252 | } |
| 253 | |
| 254 | memcpy(frame->data[1], c->pal, AVPALETTE_SIZE); |
| 255 | frame->palette_has_changed = type & BMV_PALETTE; |
| 256 | |
| 257 | outptr = frame->data[0]; |
| 258 | srcptr = c->frame; |
| 259 | |
| 260 | for (i = 0; i < avctx->height; i++) { |
| 261 | memcpy(outptr, srcptr, avctx->width); |
| 262 | srcptr += avctx->width; |
| 263 | outptr += frame->linesize[0]; |
| 264 | } |
| 265 | |
| 266 | *got_frame = 1; |
| 267 | |
| 268 | /* always report that the buffer was completely consumed */ |
| 269 | return pkt->size; |
| 270 | } |
| 271 | |
| 272 | static av_cold int decode_init(AVCodecContext *avctx) |
| 273 | { |
| 274 | BMVDecContext * const c = avctx->priv_data; |
| 275 | |
| 276 | c->avctx = avctx; |
| 277 | avctx->pix_fmt = AV_PIX_FMT_PAL8; |
| 278 | |
| 279 | if (avctx->width != SCREEN_WIDE || avctx->height != SCREEN_HIGH) { |
| 280 | av_log(avctx, AV_LOG_ERROR, "Invalid dimension %dx%d\n", avctx->width, avctx->height); |
| 281 | return AVERROR_INVALIDDATA; |
| 282 | } |
| 283 | |
| 284 | c->frame = c->frame_base + 640; |
| 285 | |
| 286 | return 0; |
| 287 | } |
| 288 | |
| 289 | AVCodec ff_bmv_video_decoder = { |
| 290 | .name = "bmv_video", |
| 291 | .long_name = NULL_IF_CONFIG_SMALL("Discworld II BMV video"), |
| 292 | .type = AVMEDIA_TYPE_VIDEO, |
| 293 | .id = AV_CODEC_ID_BMV_VIDEO, |
| 294 | .priv_data_size = sizeof(BMVDecContext), |
| 295 | .init = decode_init, |
| 296 | .decode = decode_frame, |
| 297 | .capabilities = CODEC_CAP_DR1, |
| 298 | }; |