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 
23 #include "avcodec.h"
24 #include "bytestream.h"
25 #include "internal.h"
26 
27 enum BMVFlags{
28  BMV_NOP = 0,
32 
33  BMV_SCROLL = 0x04,
34  BMV_PALETTE = 0x08,
35  BMV_COMMAND = 0x10,
36  BMV_AUDIO = 0x20,
37  BMV_EXT = 0x40,
38  BMV_PRINT = 0x80
39 };
40 
41 #define SCREEN_WIDE 640
42 #define SCREEN_HIGH 429
43 
44 typedef struct BMVDecContext {
47 
49  uint32_t pal[256];
50  const uint8_t *stream;
52 
53 #define NEXT_BYTE(v) v = forward ? v + 1 : v - 1;
54 
55 static int decode_bmv_frame(const uint8_t *source, int src_len, uint8_t *frame, int frame_off)
56 {
57  unsigned val, saved_val = 0;
58  int tmplen = src_len;
59  const uint8_t *src, *source_end = source + src_len;
60  uint8_t *frame_end = frame + SCREEN_WIDE * SCREEN_HIGH;
61  uint8_t *dst, *dst_end;
62  int len, mask;
63  int forward = (frame_off <= -SCREEN_WIDE) || (frame_off >= 0);
64  int read_two_nibbles, flag;
65  int advance_mode;
66  int mode = 0;
67  int i;
68 
69  if (src_len <= 0)
70  return -1;
71 
72  if (forward) {
73  src = source;
74  dst = frame;
75  dst_end = frame_end;
76  } else {
77  src = source + src_len - 1;
78  dst = frame_end - 1;
79  dst_end = frame - 1;
80  }
81  for (;;) {
82  int shift = 0;
83  flag = 0;
84 
85  /* The mode/len decoding is a bit strange:
86  * values are coded as variable-length codes with nibble units,
87  * code end is signalled by two top bits in the nibble being nonzero.
88  * And since data is bytepacked and we read two nibbles at a time,
89  * we may get a nibble belonging to the next code.
90  * Hence this convoluted loop.
91  */
92  if (!mode || (tmplen == 4)) {
93  if (src < source || src >= source_end)
94  return -1;
95  val = *src;
96  read_two_nibbles = 1;
97  } else {
98  val = saved_val;
99  read_two_nibbles = 0;
100  }
101  if (!(val & 0xC)) {
102  for (;;) {
103  if (!read_two_nibbles) {
104  if (src < source || src >= source_end)
105  return -1;
106  shift += 2;
107  val |= *src << shift;
108  if (*src & 0xC)
109  break;
110  }
111  // two upper bits of the nibble is zero,
112  // so shift top nibble value down into their place
113  read_two_nibbles = 0;
114  shift += 2;
115  mask = (1 << shift) - 1;
116  val = ((val >> 2) & ~mask) | (val & mask);
117  NEXT_BYTE(src);
118  if ((val & (0xC << shift))) {
119  flag = 1;
120  break;
121  }
122  }
123  } else if (mode) {
124  flag = tmplen != 4;
125  }
126  if (flag) {
127  tmplen = 4;
128  } else {
129  saved_val = val >> (4 + shift);
130  tmplen = 0;
131  val &= (1 << (shift + 4)) - 1;
132  NEXT_BYTE(src);
133  }
134  advance_mode = val & 1;
135  len = (val >> 1) - 1;
136  mode += 1 + advance_mode;
137  if (mode >= 4)
138  mode -= 3;
139  if (len <= 0 || FFABS(dst_end - dst) < len)
140  return -1;
141  switch (mode) {
142  case 1:
143  if (forward) {
144  if (dst - frame + SCREEN_WIDE < frame_off ||
145  dst - frame + SCREEN_WIDE + frame_off < 0 ||
146  frame_end - dst < frame_off + len ||
147  frame_end - dst < len)
148  return -1;
149  for (i = 0; i < len; i++)
150  dst[i] = dst[frame_off + i];
151  dst += len;
152  } else {
153  dst -= len;
154  if (dst - frame + SCREEN_WIDE < frame_off ||
155  dst - frame + SCREEN_WIDE + frame_off < 0 ||
156  frame_end - dst < frame_off + len ||
157  frame_end - dst < len)
158  return -1;
159  for (i = len - 1; i >= 0; i--)
160  dst[i] = dst[frame_off + i];
161  }
162  break;
163  case 2:
164  if (forward) {
165  if (source + src_len - src < len)
166  return -1;
167  memcpy(dst, src, len);
168  dst += len;
169  src += len;
170  } else {
171  if (src - source < len)
172  return -1;
173  dst -= len;
174  src -= len;
175  memcpy(dst, src, len);
176  }
177  break;
178  case 3:
179  val = forward ? dst[-1] : dst[1];
180  if (forward) {
181  memset(dst, val, len);
182  dst += len;
183  } else {
184  dst -= len;
185  memset(dst, val, len);
186  }
187  break;
188  default:
189  break;
190  }
191  if (dst == dst_end)
192  return 0;
193  }
194  return 0;
195 }
196 
197 static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
198  AVPacket *pkt)
199 {
200  BMVDecContext * const c = avctx->priv_data;
201  int type, scr_off;
202  int i, ret;
203  uint8_t *srcptr, *outptr;
204 
205  c->stream = pkt->data;
206  type = bytestream_get_byte(&c->stream);
207  if (type & BMV_AUDIO) {
208  int blobs = bytestream_get_byte(&c->stream);
209  if (pkt->size < blobs * 65 + 2) {
210  av_log(avctx, AV_LOG_ERROR, "Audio data doesn't fit in frame\n");
211  return AVERROR_INVALIDDATA;
212  }
213  c->stream += blobs * 65;
214  }
215  if (type & BMV_COMMAND) {
216  int command_size = (type & BMV_PRINT) ? 8 : 10;
217  if (c->stream - pkt->data + command_size > pkt->size) {
218  av_log(avctx, AV_LOG_ERROR, "Command data doesn't fit in frame\n");
219  return AVERROR_INVALIDDATA;
220  }
221  c->stream += command_size;
222  }
223  if (type & BMV_PALETTE) {
224  if (c->stream - pkt->data > pkt->size - 768) {
225  av_log(avctx, AV_LOG_ERROR, "Palette data doesn't fit in frame\n");
226  return AVERROR_INVALIDDATA;
227  }
228  for (i = 0; i < 256; i++)
229  c->pal[i] = bytestream_get_be24(&c->stream);
230  }
231  if (type & BMV_SCROLL) {
232  if (c->stream - pkt->data > pkt->size - 2) {
233  av_log(avctx, AV_LOG_ERROR, "Screen offset data doesn't fit in frame\n");
234  return AVERROR_INVALIDDATA;
235  }
236  scr_off = (int16_t)bytestream_get_le16(&c->stream);
237  } else if ((type & BMV_INTRA) == BMV_INTRA) {
238  scr_off = -640;
239  } else {
240  scr_off = 0;
241  }
242 
243  if (c->pic.data[0])
244  avctx->release_buffer(avctx, &c->pic);
245 
246  c->pic.reference = 3;
247  if ((ret = ff_get_buffer(avctx, &c->pic)) < 0) {
248  av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
249  return ret;
250  }
251 
252  if (decode_bmv_frame(c->stream, pkt->size - (c->stream - pkt->data), c->frame, scr_off)) {
253  av_log(avctx, AV_LOG_ERROR, "Error decoding frame data\n");
254  return AVERROR_INVALIDDATA;
255  }
256 
257  memcpy(c->pic.data[1], c->pal, AVPALETTE_SIZE);
258  c->pic.palette_has_changed = type & BMV_PALETTE;
259 
260  outptr = c->pic.data[0];
261  srcptr = c->frame;
262 
263  for (i = 0; i < avctx->height; i++) {
264  memcpy(outptr, srcptr, avctx->width);
265  srcptr += avctx->width;
266  outptr += c->pic.linesize[0];
267  }
268 
269  *got_frame = 1;
270  *(AVFrame*)data = c->pic;
271 
272  /* always report that the buffer was completely consumed */
273  return pkt->size;
274 }
275 
277 {
278  BMVDecContext * const c = avctx->priv_data;
279 
280  c->avctx = avctx;
281  avctx->pix_fmt = AV_PIX_FMT_PAL8;
282 
283  c->frame = c->frame_base + 640;
284 
285  return 0;
286 }
287 
289 {
290  BMVDecContext *c = avctx->priv_data;
291 
292  if (c->pic.data[0])
293  avctx->release_buffer(avctx, &c->pic);
294 
295  return 0;
296 }
297 
298 typedef struct BMVAudioDecContext {
301 
302 static const int bmv_aud_mults[16] = {
303  16512, 8256, 4128, 2064, 1032, 516, 258, 192, 129, 88, 64, 56, 48, 40, 36, 32
304 };
305 
307 {
308  BMVAudioDecContext *c = avctx->priv_data;
309 
310  avctx->channels = 2;
312  avctx->sample_fmt = AV_SAMPLE_FMT_S16;
313 
315  avctx->coded_frame = &c->frame;
316 
317  return 0;
318 }
319 
320 static int bmv_aud_decode_frame(AVCodecContext *avctx, void *data,
321  int *got_frame_ptr, AVPacket *avpkt)
322 {
323  BMVAudioDecContext *c = avctx->priv_data;
324  const uint8_t *buf = avpkt->data;
325  int buf_size = avpkt->size;
326  int blocks = 0, total_blocks, i;
327  int ret;
328  int16_t *output_samples;
329  int scale[2];
330 
331  total_blocks = *buf++;
332  if (buf_size < total_blocks * 65 + 1) {
333  av_log(avctx, AV_LOG_ERROR, "expected %d bytes, got %d\n",
334  total_blocks * 65 + 1, buf_size);
335  return AVERROR_INVALIDDATA;
336  }
337 
338  /* get output buffer */
339  c->frame.nb_samples = total_blocks * 32;
340  if ((ret = ff_get_buffer(avctx, &c->frame)) < 0) {
341  av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
342  return ret;
343  }
344  output_samples = (int16_t *)c->frame.data[0];
345 
346  for (blocks = 0; blocks < total_blocks; blocks++) {
347  uint8_t code = *buf++;
348  code = (code >> 1) | (code << 7);
349  scale[0] = bmv_aud_mults[code & 0xF];
350  scale[1] = bmv_aud_mults[code >> 4];
351  for (i = 0; i < 32; i++) {
352  *output_samples++ = av_clip_int16((scale[0] * (int8_t)*buf++) >> 5);
353  *output_samples++ = av_clip_int16((scale[1] * (int8_t)*buf++) >> 5);
354  }
355  }
356 
357  *got_frame_ptr = 1;
358  *(AVFrame *)data = c->frame;
359 
360  return buf_size;
361 }
362 
364  .name = "bmv_video",
365  .type = AVMEDIA_TYPE_VIDEO,
366  .id = AV_CODEC_ID_BMV_VIDEO,
367  .priv_data_size = sizeof(BMVDecContext),
368  .init = decode_init,
369  .close = decode_end,
370  .decode = decode_frame,
371  .capabilities = CODEC_CAP_DR1,
372  .long_name = NULL_IF_CONFIG_SMALL("Discworld II BMV video"),
373 };
374 
376  .name = "bmv_audio",
377  .type = AVMEDIA_TYPE_AUDIO,
378  .id = AV_CODEC_ID_BMV_AUDIO,
379  .priv_data_size = sizeof(BMVAudioDecContext),
382  .capabilities = CODEC_CAP_DR1,
383  .long_name = NULL_IF_CONFIG_SMALL("Discworld II BMV audio"),
384 };