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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 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/channel_layout.h"
24 #include "avcodec.h"
25 #include "bytestream.h"
26 #include "internal.h"
27 
28 enum BMVFlags{
29  BMV_NOP = 0,
30  BMV_END,
31  BMV_DELTA,
32  BMV_INTRA,
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 {
46  AVCodecContext *avctx;
47 
48  uint8_t *frame, frame_base[SCREEN_WIDE * (SCREEN_HIGH + 1)];
49  uint32_t pal[256];
50  const uint8_t *stream;
51 } BMVDecContext;
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 AVERROR_INVALIDDATA;
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 AVERROR_INVALIDDATA;
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(shift>22)
104  return -1;
105  if (!read_two_nibbles) {
106  if (src < source || src >= source_end)
107  return AVERROR_INVALIDDATA;
108  shift += 2;
109  val |= *src << shift;
110  if (*src & 0xC)
111  break;
112  }
113  // two upper bits of the nibble is zero,
114  // so shift top nibble value down into their place
115  read_two_nibbles = 0;
116  shift += 2;
117  mask = (1 << shift) - 1;
118  val = ((val >> 2) & ~mask) | (val & mask);
119  NEXT_BYTE(src);
120  if ((val & (0xC << shift))) {
121  flag = 1;
122  break;
123  }
124  }
125  } else if (mode) {
126  flag = tmplen != 4;
127  }
128  if (flag) {
129  tmplen = 4;
130  } else {
131  saved_val = val >> (4 + shift);
132  tmplen = 0;
133  val &= (1 << (shift + 4)) - 1;
134  NEXT_BYTE(src);
135  }
136  advance_mode = val & 1;
137  len = (val >> 1) - 1;
138  av_assert0(len>0);
139  mode += 1 + advance_mode;
140  if (mode >= 4)
141  mode -= 3;
142  if (len <= 0 || FFABS(dst_end - dst) < len)
143  return AVERROR_INVALIDDATA;
144  switch (mode) {
145  case 1:
146  if (forward) {
147  if (dst - frame + SCREEN_WIDE < frame_off ||
148  dst - frame + SCREEN_WIDE + frame_off < 0 ||
149  frame_end - dst < frame_off + len ||
150  frame_end - dst < len)
151  return AVERROR_INVALIDDATA;
152  for (i = 0; i < len; i++)
153  dst[i] = dst[frame_off + i];
154  dst += len;
155  } else {
156  dst -= len;
157  if (dst - frame + SCREEN_WIDE < frame_off ||
158  dst - frame + SCREEN_WIDE + frame_off < 0 ||
159  frame_end - dst < frame_off + len ||
160  frame_end - dst < len)
161  return AVERROR_INVALIDDATA;
162  for (i = len - 1; i >= 0; i--)
163  dst[i] = dst[frame_off + i];
164  }
165  break;
166  case 2:
167  if (forward) {
168  if (source + src_len - src < len)
169  return AVERROR_INVALIDDATA;
170  memcpy(dst, src, len);
171  dst += len;
172  src += len;
173  } else {
174  if (src - source < len)
175  return AVERROR_INVALIDDATA;
176  dst -= len;
177  src -= len;
178  memcpy(dst, src, len);
179  }
180  break;
181  case 3:
182  val = forward ? dst[-1] : dst[1];
183  if (forward) {
184  memset(dst, val, len);
185  dst += len;
186  } else {
187  dst -= len;
188  memset(dst, val, len);
189  }
190  break;
191  }
192  if (dst == dst_end)
193  return 0;
194  }
195  return 0;
196 }
197 
198 static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
199  AVPacket *pkt)
200 {
201  BMVDecContext * const c = avctx->priv_data;
202  AVFrame *frame = 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 ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
246  return ret;
247 
248  if (decode_bmv_frame(c->stream, pkt->size - (c->stream - pkt->data), c->frame, scr_off)) {
249  av_log(avctx, AV_LOG_ERROR, "Error decoding frame data\n");
250  return AVERROR_INVALIDDATA;
251  }
252 
253  memcpy(frame->data[1], c->pal, AVPALETTE_SIZE);
254  frame->palette_has_changed = type & BMV_PALETTE;
255 
256  outptr = frame->data[0];
257  srcptr = c->frame;
258 
259  for (i = 0; i < avctx->height; i++) {
260  memcpy(outptr, srcptr, avctx->width);
261  srcptr += avctx->width;
262  outptr += frame->linesize[0];
263  }
264 
265  *got_frame = 1;
266 
267  /* always report that the buffer was completely consumed */
268  return pkt->size;
269 }
270 
271 static av_cold int decode_init(AVCodecContext *avctx)
272 {
273  BMVDecContext * const c = avctx->priv_data;
274 
275  c->avctx = avctx;
276  avctx->pix_fmt = AV_PIX_FMT_PAL8;
277 
278  if (avctx->width != SCREEN_WIDE || avctx->height != SCREEN_HIGH) {
279  av_log(avctx, AV_LOG_ERROR, "Invalid dimension %dx%d\n", avctx->width, avctx->height);
280  return AVERROR_INVALIDDATA;
281  }
282 
283  c->frame = c->frame_base + 640;
284 
285  return 0;
286 }
287 
288 static const int bmv_aud_mults[16] = {
289  16512, 8256, 4128, 2064, 1032, 516, 258, 192, 129, 88, 64, 56, 48, 40, 36, 32
290 };
291 
292 static av_cold int bmv_aud_decode_init(AVCodecContext *avctx)
293 {
294  avctx->channels = 2;
295  avctx->channel_layout = AV_CH_LAYOUT_STEREO;
296  avctx->sample_fmt = AV_SAMPLE_FMT_S16;
297 
298  return 0;
299 }
300 
301 static int bmv_aud_decode_frame(AVCodecContext *avctx, void *data,
302  int *got_frame_ptr, AVPacket *avpkt)
303 {
304  AVFrame *frame = data;
305  const uint8_t *buf = avpkt->data;
306  int buf_size = avpkt->size;
307  int blocks = 0, total_blocks, i;
308  int ret;
309  int16_t *output_samples;
310  int scale[2];
311 
312  total_blocks = *buf++;
313  if (buf_size < total_blocks * 65 + 1) {
314  av_log(avctx, AV_LOG_ERROR, "expected %d bytes, got %d\n",
315  total_blocks * 65 + 1, buf_size);
316  return AVERROR_INVALIDDATA;
317  }
318 
319  /* get output buffer */
320  frame->nb_samples = total_blocks * 32;
321  if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
322  return ret;
323  output_samples = (int16_t *)frame->data[0];
324 
325  for (blocks = 0; blocks < total_blocks; blocks++) {
326  uint8_t code = *buf++;
327  code = (code >> 1) | (code << 7);
328  scale[0] = bmv_aud_mults[code & 0xF];
329  scale[1] = bmv_aud_mults[code >> 4];
330  for (i = 0; i < 32; i++) {
331  *output_samples++ = av_clip_int16((scale[0] * (int8_t)*buf++) >> 5);
332  *output_samples++ = av_clip_int16((scale[1] * (int8_t)*buf++) >> 5);
333  }
334  }
335 
336  *got_frame_ptr = 1;
337 
338  return buf_size;
339 }
340 
341 AVCodec ff_bmv_video_decoder = {
342  .name = "bmv_video",
343  .long_name = NULL_IF_CONFIG_SMALL("Discworld II BMV video"),
344  .type = AVMEDIA_TYPE_VIDEO,
345  .id = AV_CODEC_ID_BMV_VIDEO,
346  .priv_data_size = sizeof(BMVDecContext),
347  .init = decode_init,
348  .decode = decode_frame,
349  .capabilities = CODEC_CAP_DR1,
350 };
351 
352 AVCodec ff_bmv_audio_decoder = {
353  .name = "bmv_audio",
354  .long_name = NULL_IF_CONFIG_SMALL("Discworld II BMV audio"),
355  .type = AVMEDIA_TYPE_AUDIO,
356  .id = AV_CODEC_ID_BMV_AUDIO,
357  .init = bmv_aud_decode_init,
358  .decode = bmv_aud_decode_frame,
359  .capabilities = CODEC_CAP_DR1,
360 };
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