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 "avcodec.h"
23 #include "bytestream.h"
24 
25 enum BMVFlags{
26  BMV_NOP = 0,
30 
31  BMV_SCROLL = 0x04,
32  BMV_PALETTE = 0x08,
33  BMV_COMMAND = 0x10,
34  BMV_AUDIO = 0x20,
35  BMV_EXT = 0x40,
36  BMV_PRINT = 0x80
37 };
38 
39 #define SCREEN_WIDE 640
40 #define SCREEN_HIGH 429
41 
42 typedef struct BMVDecContext {
45 
47  uint32_t pal[256];
48  const uint8_t *stream;
50 
51 #define NEXT_BYTE(v) v = forward ? v + 1 : v - 1;
52 
53 static int decode_bmv_frame(const uint8_t *source, int src_len, uint8_t *frame, int frame_off)
54 {
55  int val, saved_val = 0;
56  int tmplen = src_len;
57  const uint8_t *src, *source_end = source + src_len;
58  uint8_t *frame_end = frame + SCREEN_WIDE * SCREEN_HIGH;
59  uint8_t *dst, *dst_end;
60  int len, mask;
61  int forward = (frame_off <= -SCREEN_WIDE) || (frame_off >= 0);
62  int read_two_nibbles, flag;
63  int advance_mode;
64  int mode = 0;
65  int i;
66 
67  if (src_len <= 0)
68  return -1;
69 
70  if (forward) {
71  src = source;
72  dst = frame;
73  dst_end = frame_end;
74  } else {
75  src = source + src_len - 1;
76  dst = frame_end - 1;
77  dst_end = frame - 1;
78  }
79  for (;;) {
80  int shift = 0;
81  flag = 0;
82 
83  /* The mode/len decoding is a bit strange:
84  * values are coded as variable-length codes with nibble units,
85  * code end is signalled by two top bits in the nibble being nonzero.
86  * And since data is bytepacked and we read two nibbles at a time,
87  * we may get a nibble belonging to the next code.
88  * Hence this convoluted loop.
89  */
90  if (!mode || (tmplen == 4)) {
91  if (src < source || src >= source_end)
92  return -1;
93  val = *src;
94  read_two_nibbles = 1;
95  } else {
96  val = saved_val;
97  read_two_nibbles = 0;
98  }
99  if (!(val & 0xC)) {
100  for (;;) {
101  if (!read_two_nibbles) {
102  if (src < source || src >= source_end)
103  return -1;
104  shift += 2;
105  val |= *src << shift;
106  if (*src & 0xC)
107  break;
108  }
109  // two upper bits of the nibble is zero,
110  // so shift top nibble value down into their place
111  read_two_nibbles = 0;
112  shift += 2;
113  mask = (1 << shift) - 1;
114  val = ((val >> 2) & ~mask) | (val & mask);
115  NEXT_BYTE(src);
116  if ((val & (0xC << shift))) {
117  flag = 1;
118  break;
119  }
120  }
121  } else if (mode) {
122  flag = tmplen != 4;
123  }
124  if (flag) {
125  tmplen = 4;
126  } else {
127  saved_val = val >> (4 + shift);
128  tmplen = 0;
129  val &= (1 << (shift + 4)) - 1;
130  NEXT_BYTE(src);
131  }
132  advance_mode = val & 1;
133  len = (val >> 1) - 1;
134  mode += 1 + advance_mode;
135  if (mode >= 4)
136  mode -= 3;
137  if (FFABS(dst_end - dst) < len)
138  return -1;
139  switch (mode) {
140  case 1:
141  if (forward) {
142  if (dst - frame + SCREEN_WIDE < frame_off ||
143  frame_end - dst < frame_off + len)
144  return -1;
145  for (i = 0; i < len; i++)
146  dst[i] = dst[frame_off + i];
147  dst += len;
148  } else {
149  dst -= len;
150  if (dst - frame + SCREEN_WIDE < frame_off ||
151  frame_end - dst < frame_off + len)
152  return -1;
153  for (i = len - 1; i >= 0; i--)
154  dst[i] = dst[frame_off + i];
155  }
156  break;
157  case 2:
158  if (forward) {
159  if (source + src_len - src < len)
160  return -1;
161  memcpy(dst, src, len);
162  dst += len;
163  src += len;
164  } else {
165  if (src - source < len)
166  return -1;
167  dst -= len;
168  src -= len;
169  memcpy(dst, src, len);
170  }
171  break;
172  case 3:
173  val = forward ? dst[-1] : dst[1];
174  if (forward) {
175  memset(dst, val, len);
176  dst += len;
177  } else {
178  dst -= len;
179  memset(dst, val, len);
180  }
181  break;
182  default:
183  break;
184  }
185  if (dst == dst_end)
186  return 0;
187  }
188  return 0;
189 }
190 
191 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *pkt)
192 {
193  BMVDecContext * const c = avctx->priv_data;
194  int type, scr_off;
195  int i;
196  uint8_t *srcptr, *outptr;
197 
198  c->stream = pkt->data;
199  type = bytestream_get_byte(&c->stream);
200  if (type & BMV_AUDIO) {
201  int blobs = bytestream_get_byte(&c->stream);
202  if (pkt->size < blobs * 65 + 2) {
203  av_log(avctx, AV_LOG_ERROR, "Audio data doesn't fit in frame\n");
204  return AVERROR_INVALIDDATA;
205  }
206  c->stream += blobs * 65;
207  }
208  if (type & BMV_COMMAND) {
209  int command_size = (type & BMV_PRINT) ? 8 : 10;
210  if (c->stream - pkt->data + command_size > pkt->size) {
211  av_log(avctx, AV_LOG_ERROR, "Command data doesn't fit in frame\n");
212  return AVERROR_INVALIDDATA;
213  }
214  c->stream += command_size;
215  }
216  if (type & BMV_PALETTE) {
217  if (c->stream - pkt->data > pkt->size - 768) {
218  av_log(avctx, AV_LOG_ERROR, "Palette data doesn't fit in frame\n");
219  return AVERROR_INVALIDDATA;
220  }
221  for (i = 0; i < 256; i++)
222  c->pal[i] = bytestream_get_be24(&c->stream);
223  }
224  if (type & BMV_SCROLL) {
225  if (c->stream - pkt->data > pkt->size - 2) {
226  av_log(avctx, AV_LOG_ERROR, "Screen offset data doesn't fit in frame\n");
227  return AVERROR_INVALIDDATA;
228  }
229  scr_off = (int16_t)bytestream_get_le16(&c->stream);
230  } else if ((type & BMV_INTRA) == BMV_INTRA) {
231  scr_off = -640;
232  } else {
233  scr_off = 0;
234  }
235 
236  if (decode_bmv_frame(c->stream, pkt->size - (c->stream - pkt->data), c->frame, scr_off)) {
237  av_log(avctx, AV_LOG_ERROR, "Error decoding frame data\n");
238  return AVERROR_INVALIDDATA;
239  }
240 
241  memcpy(c->pic.data[1], c->pal, AVPALETTE_SIZE);
242  c->pic.palette_has_changed = type & BMV_PALETTE;
243 
244  outptr = c->pic.data[0];
245  srcptr = c->frame;
246 
247  for (i = 0; i < avctx->height; i++) {
248  memcpy(outptr, srcptr, avctx->width);
249  srcptr += avctx->width;
250  outptr += c->pic.linesize[0];
251  }
252 
253  *data_size = sizeof(AVFrame);
254  *(AVFrame*)data = c->pic;
255 
256  /* always report that the buffer was completely consumed */
257  return pkt->size;
258 }
259 
261 {
262  BMVDecContext * const c = avctx->priv_data;
263 
264  c->avctx = avctx;
265  avctx->pix_fmt = PIX_FMT_PAL8;
266 
267  c->pic.reference = 1;
268  if (avctx->get_buffer(avctx, &c->pic) < 0) {
269  av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
270  return -1;
271  }
272 
273  c->frame = c->frame_base + 640;
274 
275  return 0;
276 }
277 
279 {
280  BMVDecContext *c = avctx->priv_data;
281 
282  if (c->pic.data[0])
283  avctx->release_buffer(avctx, &c->pic);
284 
285  return 0;
286 }
287 
288 typedef struct BMVAudioDecContext {
291 
292 static const int bmv_aud_mults[16] = {
293  16512, 8256, 4128, 2064, 1032, 516, 258, 192, 129, 88, 64, 56, 48, 40, 36, 32
294 };
295 
297 {
298  BMVAudioDecContext *c = avctx->priv_data;
299 
300  if (avctx->channels != 2) {
301  av_log(avctx, AV_LOG_INFO, "invalid number of channels\n");
302  return AVERROR(EINVAL);
303  }
304 
305  avctx->sample_fmt = AV_SAMPLE_FMT_S16;
306 
308  avctx->coded_frame = &c->frame;
309 
310  return 0;
311 }
312 
313 static int bmv_aud_decode_frame(AVCodecContext *avctx, void *data,
314  int *got_frame_ptr, AVPacket *avpkt)
315 {
316  BMVAudioDecContext *c = avctx->priv_data;
317  const uint8_t *buf = avpkt->data;
318  int buf_size = avpkt->size;
319  int blocks = 0, total_blocks, i;
320  int ret;
321  int16_t *output_samples;
322  int scale[2];
323 
324  total_blocks = *buf++;
325  if (buf_size < total_blocks * 65 + 1) {
326  av_log(avctx, AV_LOG_ERROR, "expected %d bytes, got %d\n",
327  total_blocks * 65 + 1, buf_size);
328  return AVERROR_INVALIDDATA;
329  }
330 
331  /* get output buffer */
332  c->frame.nb_samples = total_blocks * 32;
333  if ((ret = avctx->get_buffer(avctx, &c->frame)) < 0) {
334  av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
335  return ret;
336  }
337  output_samples = (int16_t *)c->frame.data[0];
338 
339  for (blocks = 0; blocks < total_blocks; blocks++) {
340  uint8_t code = *buf++;
341  code = (code >> 1) | (code << 7);
342  scale[0] = bmv_aud_mults[code & 0xF];
343  scale[1] = bmv_aud_mults[code >> 4];
344  for (i = 0; i < 32; i++) {
345  *output_samples++ = av_clip_int16((scale[0] * (int8_t)*buf++) >> 5);
346  *output_samples++ = av_clip_int16((scale[1] * (int8_t)*buf++) >> 5);
347  }
348  }
349 
350  *got_frame_ptr = 1;
351  *(AVFrame *)data = c->frame;
352 
353  return buf_size;
354 }
355 
357  .name = "bmv_video",
358  .type = AVMEDIA_TYPE_VIDEO,
359  .id = CODEC_ID_BMV_VIDEO,
360  .priv_data_size = sizeof(BMVDecContext),
361  .init = decode_init,
362  .close = decode_end,
363  .decode = decode_frame,
364  .long_name = NULL_IF_CONFIG_SMALL("Discworld II BMV video"),
365 };
366 
368  .name = "bmv_audio",
369  .type = AVMEDIA_TYPE_AUDIO,
370  .id = CODEC_ID_BMV_AUDIO,
371  .priv_data_size = sizeof(BMVAudioDecContext),
374  .capabilities = CODEC_CAP_DR1,
375  .long_name = NULL_IF_CONFIG_SMALL("Discworld II BMV audio"),
376 };