dvdsubenc.c
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1 /*
2  * DVD subtitle encoding
3  * Copyright (c) 2005 Wolfram Gloger
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 #include "avcodec.h"
22 #include "bytestream.h"
23 
24 #undef NDEBUG
25 #include <assert.h>
26 
27 // ncnt is the nibble counter
28 #define PUTNIBBLE(val)\
29 do {\
30  if (ncnt++ & 1)\
31  *q++ = bitbuf | ((val) & 0x0f);\
32  else\
33  bitbuf = (val) << 4;\
34 } while(0)
35 
36 static void dvd_encode_rle(uint8_t **pq,
37  const uint8_t *bitmap, int linesize,
38  int w, int h,
39  const int cmap[256])
40 {
41  uint8_t *q;
42  unsigned int bitbuf = 0;
43  int ncnt;
44  int x, y, len, color;
45 
46  q = *pq;
47 
48  for (y = 0; y < h; ++y) {
49  ncnt = 0;
50  for(x = 0; x < w; x += len) {
51  color = bitmap[x];
52  for (len=1; x+len < w; ++len)
53  if (bitmap[x+len] != color)
54  break;
55  color = cmap[color];
56  assert(color < 4);
57  if (len < 0x04) {
58  PUTNIBBLE((len << 2)|color);
59  } else if (len < 0x10) {
60  PUTNIBBLE(len >> 2);
61  PUTNIBBLE((len << 2)|color);
62  } else if (len < 0x40) {
63  PUTNIBBLE(0);
64  PUTNIBBLE(len >> 2);
65  PUTNIBBLE((len << 2)|color);
66  } else if (x+len == w) {
67  PUTNIBBLE(0);
68  PUTNIBBLE(0);
69  PUTNIBBLE(0);
70  PUTNIBBLE(color);
71  } else {
72  if (len > 0xff)
73  len = 0xff;
74  PUTNIBBLE(0);
75  PUTNIBBLE(len >> 6);
76  PUTNIBBLE(len >> 2);
77  PUTNIBBLE((len << 2)|color);
78  }
79  }
80  /* end of line */
81  if (ncnt & 1)
82  PUTNIBBLE(0);
83  bitmap += linesize;
84  }
85 
86  *pq = q;
87 }
88 
89 static int encode_dvd_subtitles(uint8_t *outbuf, int outbuf_size,
90  const AVSubtitle *h)
91 {
92  uint8_t *q, *qq;
93  int object_id;
94  int offset1[20], offset2[20];
95  int i, imax, color, alpha, rects = h->num_rects;
96  unsigned long hmax;
97  unsigned long hist[256];
98  int cmap[256];
99 
100  if (rects == 0 || h->rects == NULL)
101  return -1;
102  if (rects > 20)
103  rects = 20;
104 
105  // analyze bitmaps, compress to 4 colors
106  for (i=0; i<256; ++i) {
107  hist[i] = 0;
108  cmap[i] = 0;
109  }
110  for (object_id = 0; object_id < rects; object_id++)
111  for (i=0; i<h->rects[object_id]->w*h->rects[object_id]->h; ++i) {
112  color = h->rects[object_id]->pict.data[0][i];
113  // only count non-transparent pixels
114  alpha = ((uint32_t*)h->rects[object_id]->pict.data[1])[color] >> 24;
115  hist[color] += alpha;
116  }
117  for (color=3;; --color) {
118  hmax = 0;
119  imax = 0;
120  for (i=0; i<256; ++i)
121  if (hist[i] > hmax) {
122  imax = i;
123  hmax = hist[i];
124  }
125  if (hmax == 0)
126  break;
127  if (color == 0)
128  color = 3;
129  av_log(NULL, AV_LOG_DEBUG, "dvd_subtitle hist[%d]=%ld -> col %d\n",
130  imax, hist[imax], color);
131  cmap[imax] = color;
132  hist[imax] = 0;
133  }
134 
135 
136  // encode data block
137  q = outbuf + 4;
138  for (object_id = 0; object_id < rects; object_id++) {
139  offset1[object_id] = q - outbuf;
140  // worst case memory requirement: 1 nibble per pixel..
141  if ((q - outbuf) + h->rects[object_id]->w*h->rects[object_id]->h/2
142  + 17*rects + 21 > outbuf_size) {
143  av_log(NULL, AV_LOG_ERROR, "dvd_subtitle too big\n");
144  return -1;
145  }
146  dvd_encode_rle(&q, h->rects[object_id]->pict.data[0],
147  h->rects[object_id]->w*2,
148  h->rects[object_id]->w, h->rects[object_id]->h >> 1,
149  cmap);
150  offset2[object_id] = q - outbuf;
151  dvd_encode_rle(&q, h->rects[object_id]->pict.data[0] + h->rects[object_id]->w,
152  h->rects[object_id]->w*2,
153  h->rects[object_id]->w, h->rects[object_id]->h >> 1,
154  cmap);
155  }
156 
157  // set data packet size
158  qq = outbuf + 2;
159  bytestream_put_be16(&qq, q - outbuf);
160 
161  // send start display command
162  bytestream_put_be16(&q, (h->start_display_time*90) >> 10);
163  bytestream_put_be16(&q, (q - outbuf) /*- 2 */ + 8 + 12*rects + 2);
164  *q++ = 0x03; // palette - 4 nibbles
165  *q++ = 0x03; *q++ = 0x7f;
166  *q++ = 0x04; // alpha - 4 nibbles
167  *q++ = 0xf0; *q++ = 0x00;
168  //*q++ = 0x0f; *q++ = 0xff;
169 
170  // XXX not sure if more than one rect can really be encoded..
171  // 12 bytes per rect
172  for (object_id = 0; object_id < rects; object_id++) {
173  int x2 = h->rects[object_id]->x + h->rects[object_id]->w - 1;
174  int y2 = h->rects[object_id]->y + h->rects[object_id]->h - 1;
175 
176  *q++ = 0x05;
177  // x1 x2 -> 6 nibbles
178  *q++ = h->rects[object_id]->x >> 4;
179  *q++ = (h->rects[object_id]->x << 4) | ((x2 >> 8) & 0xf);
180  *q++ = x2;
181  // y1 y2 -> 6 nibbles
182  *q++ = h->rects[object_id]->y >> 4;
183  *q++ = (h->rects[object_id]->y << 4) | ((y2 >> 8) & 0xf);
184  *q++ = y2;
185 
186  *q++ = 0x06;
187  // offset1, offset2
188  bytestream_put_be16(&q, offset1[object_id]);
189  bytestream_put_be16(&q, offset2[object_id]);
190  }
191  *q++ = 0x01; // start command
192  *q++ = 0xff; // terminating command
193 
194  // send stop display command last
195  bytestream_put_be16(&q, (h->end_display_time*90) >> 10);
196  bytestream_put_be16(&q, (q - outbuf) - 2 /*+ 4*/);
197  *q++ = 0x02; // set end
198  *q++ = 0xff; // terminating command
199 
200  qq = outbuf;
201  bytestream_put_be16(&qq, q - outbuf);
202 
203  av_log(NULL, AV_LOG_DEBUG, "subtitle_packet size=%td\n", q - outbuf);
204  return q - outbuf;
205 }
206 
207 static int dvdsub_encode(AVCodecContext *avctx,
208  unsigned char *buf, int buf_size, void *data)
209 {
210  //DVDSubtitleContext *s = avctx->priv_data;
211  AVSubtitle *sub = data;
212  int ret;
213 
214  ret = encode_dvd_subtitles(buf, buf_size, sub);
215  return ret;
216 }
217 
219  .name = "dvdsub",
220  .type = AVMEDIA_TYPE_SUBTITLE,
221  .id = CODEC_ID_DVD_SUBTITLE,
222  .encode = dvdsub_encode,
223  .long_name = NULL_IF_CONFIG_SMALL("DVD subtitles"),
224 };