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bmvvideo.c
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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,
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 {
48 
50  uint32_t pal[256];
51  const uint8_t *stream;
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;
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 
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 
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 };