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bmv.c
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1 /*
2  * Discworld II BMV video and audio decoder
3  * Copyright (c) 2011 Konstantin Shishkov
4  *
5  * This file is part of Libav.
6  *
7  * Libav 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  * Libav 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 Libav; 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"
24 #include "avcodec.h"
25 #include "bytestream.h"
26 #include "internal.h"
27 
28 enum BMVFlags{
29  BMV_NOP = 0,
33 
34  BMV_SCROLL = 0x04,
35  BMV_PALETTE = 0x08,
36  BMV_COMMAND = 0x10,
37  BMV_AUDIO = 0x20,
38  BMV_EXT = 0x40,
39  BMV_PRINT = 0x80
40 };
41 
42 #define SCREEN_WIDE 640
43 #define SCREEN_HIGH 429
44 
45 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;
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 (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  int type, scr_off;
204  int i, ret;
205  uint8_t *srcptr, *outptr;
206 
207  c->stream = pkt->data;
208  type = bytestream_get_byte(&c->stream);
209  if (type & BMV_AUDIO) {
210  int blobs = bytestream_get_byte(&c->stream);
211  if (pkt->size < blobs * 65 + 2) {
212  av_log(avctx, AV_LOG_ERROR, "Audio data doesn't fit in frame\n");
213  return AVERROR_INVALIDDATA;
214  }
215  c->stream += blobs * 65;
216  }
217  if (type & BMV_COMMAND) {
218  int command_size = (type & BMV_PRINT) ? 8 : 10;
219  if (c->stream - pkt->data + command_size > pkt->size) {
220  av_log(avctx, AV_LOG_ERROR, "Command data doesn't fit in frame\n");
221  return AVERROR_INVALIDDATA;
222  }
223  c->stream += command_size;
224  }
225  if (type & BMV_PALETTE) {
226  if (c->stream - pkt->data > pkt->size - 768) {
227  av_log(avctx, AV_LOG_ERROR, "Palette data doesn't fit in frame\n");
228  return AVERROR_INVALIDDATA;
229  }
230  for (i = 0; i < 256; i++)
231  c->pal[i] = 0xFFU << 24 | bytestream_get_be24(&c->stream);
232  }
233  if (type & BMV_SCROLL) {
234  if (c->stream - pkt->data > pkt->size - 2) {
235  av_log(avctx, AV_LOG_ERROR, "Screen offset data doesn't fit in frame\n");
236  return AVERROR_INVALIDDATA;
237  }
238  scr_off = (int16_t)bytestream_get_le16(&c->stream);
239  } else if ((type & BMV_INTRA) == BMV_INTRA) {
240  scr_off = -640;
241  } else {
242  scr_off = 0;
243  }
244 
245  if (c->pic.data[0])
246  avctx->release_buffer(avctx, &c->pic);
247 
248  c->pic.reference = 3;
249  if ((ret = ff_get_buffer(avctx, &c->pic)) < 0) {
250  av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
251  return ret;
252  }
253 
254  if (decode_bmv_frame(c->stream, pkt->size - (c->stream - pkt->data), c->frame, scr_off)) {
255  av_log(avctx, AV_LOG_ERROR, "Error decoding frame data\n");
256  return AVERROR_INVALIDDATA;
257  }
258 
259  memcpy(c->pic.data[1], c->pal, AVPALETTE_SIZE);
260  c->pic.palette_has_changed = type & BMV_PALETTE;
261 
262  outptr = c->pic.data[0];
263  srcptr = c->frame;
264 
265  for (i = 0; i < avctx->height; i++) {
266  memcpy(outptr, srcptr, avctx->width);
267  srcptr += avctx->width;
268  outptr += c->pic.linesize[0];
269  }
270 
271  *got_frame = 1;
272  *(AVFrame*)data = c->pic;
273 
274  /* always report that the buffer was completely consumed */
275  return pkt->size;
276 }
277 
279 {
280  BMVDecContext * const c = avctx->priv_data;
281 
282  c->avctx = avctx;
283  avctx->pix_fmt = AV_PIX_FMT_PAL8;
284 
285  if (avctx->width != SCREEN_WIDE || avctx->height != SCREEN_HIGH) {
286  av_log(avctx, AV_LOG_ERROR, "Invalid dimension %dx%d\n", avctx->width, avctx->height);
287  return AVERROR_INVALIDDATA;
288  }
289 
290  c->frame = c->frame_base + 640;
291 
292  return 0;
293 }
294 
296 {
297  BMVDecContext *c = avctx->priv_data;
298 
299  if (c->pic.data[0])
300  avctx->release_buffer(avctx, &c->pic);
301 
302  return 0;
303 }
304 
305 static const int bmv_aud_mults[16] = {
306  16512, 8256, 4128, 2064, 1032, 516, 258, 192, 129, 88, 64, 56, 48, 40, 36, 32
307 };
308 
310 {
311  avctx->channels = 2;
313  avctx->sample_fmt = AV_SAMPLE_FMT_S16;
314 
315  return 0;
316 }
317 
318 static int bmv_aud_decode_frame(AVCodecContext *avctx, void *data,
319  int *got_frame_ptr, AVPacket *avpkt)
320 {
321  AVFrame *frame = data;
322  const uint8_t *buf = avpkt->data;
323  int buf_size = avpkt->size;
324  int blocks = 0, total_blocks, i;
325  int ret;
326  int16_t *output_samples;
327  int scale[2];
328 
329  total_blocks = *buf++;
330  if (buf_size < total_blocks * 65 + 1) {
331  av_log(avctx, AV_LOG_ERROR, "expected %d bytes, got %d\n",
332  total_blocks * 65 + 1, buf_size);
333  return AVERROR_INVALIDDATA;
334  }
335 
336  /* get output buffer */
337  frame->nb_samples = total_blocks * 32;
338  if ((ret = ff_get_buffer(avctx, frame)) < 0) {
339  av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
340  return ret;
341  }
342  output_samples = (int16_t *)frame->data[0];
343 
344  for (blocks = 0; blocks < total_blocks; blocks++) {
345  uint8_t code = *buf++;
346  code = (code >> 1) | (code << 7);
347  scale[0] = bmv_aud_mults[code & 0xF];
348  scale[1] = bmv_aud_mults[code >> 4];
349  for (i = 0; i < 32; i++) {
350  *output_samples++ = av_clip_int16((scale[0] * (int8_t)*buf++) >> 5);
351  *output_samples++ = av_clip_int16((scale[1] * (int8_t)*buf++) >> 5);
352  }
353  }
354 
355  *got_frame_ptr = 1;
356 
357  return buf_size;
358 }
359 
361  .name = "bmv_video",
362  .type = AVMEDIA_TYPE_VIDEO,
363  .id = AV_CODEC_ID_BMV_VIDEO,
364  .priv_data_size = sizeof(BMVDecContext),
365  .init = decode_init,
366  .close = decode_end,
367  .decode = decode_frame,
368  .capabilities = CODEC_CAP_DR1,
369  .long_name = NULL_IF_CONFIG_SMALL("Discworld II BMV video"),
370 };
371 
373  .name = "bmv_audio",
374  .type = AVMEDIA_TYPE_AUDIO,
375  .id = AV_CODEC_ID_BMV_AUDIO,
376  .init = bmv_aud_decode_init,
377  .decode = bmv_aud_decode_frame,
378  .capabilities = CODEC_CAP_DR1,
379  .long_name = NULL_IF_CONFIG_SMALL("Discworld II BMV audio"),
380 };