libavcodec/dvdsubenc.c

   1 /*
   2  * DVD subtitle encoding for ffmpeg
   3  * Copyright (c) 2005 Wolfram Gloger.
   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 #include "avcodec.h"
  22
  23 #undef NDEBUG
  24 #include <assert.h>
  25
  26 // ncnt is the nibble counter
  27 #define PUTNIBBLE(val)\
  28 do {\
  29     if (ncnt++ & 1)\
  30         *q++ = bitbuf | ((val) & 0x0f);\
  31     else\
  32         bitbuf = (val) << 4;\
  33 } while(0)
  34
  35 static void dvd_encode_rle(uint8_t **pq,
  36                            const uint8_t *bitmap, int linesize,
  37                            int w, int h,
  38                            const int cmap[256])
  39 {
  40     uint8_t *q;
  41     unsigned int bitbuf = 0;
  42     int ncnt;
  43     int x, y, len, color;
  44
  45     q = *pq;
  46
  47     for (y = 0; y < h; ++y) {
  48         ncnt = 0;
  49         for(x = 0; x < w; x += len) {
  50             color = bitmap[x];
  51             for (len=1; x+len < w; ++len)
  52                 if (bitmap[x+len] != color)
  53                     break;
  54             color = cmap[color];
  55             assert(color < 4);
  56             if (len < 0x04) {
  57                 PUTNIBBLE((len << 2)|color);
  58             } else if (len < 0x10) {
  59                 PUTNIBBLE(len >> 2);
  60                 PUTNIBBLE((len << 2)|color);
  61             } else if (len < 0x40) {
  62                 PUTNIBBLE(0);
  63                 PUTNIBBLE(len >> 2);
  64                 PUTNIBBLE((len << 2)|color);
  65             } else if (x+len == w) {
  66                 PUTNIBBLE(0);
  67                 PUTNIBBLE(0);
  68                 PUTNIBBLE(0);
  69                 PUTNIBBLE(color);
  70             } else {
  71                 if (len > 0xff)
  72                     len = 0xff;
  73                 PUTNIBBLE(0);
  74                 PUTNIBBLE(len >> 6);
  75                 PUTNIBBLE(len >> 2);
  76                 PUTNIBBLE((len << 2)|color);
  77             }
  78         }
  79         /* end of line */
  80         if (ncnt & 1)
  81             PUTNIBBLE(0);
  82         bitmap += linesize;
  83     }
  84
  85     *pq = q;
  86 }
  87
  88 static inline void putbe16(uint8_t **pq, uint16_t v)
  89 {
  90     uint8_t *q = *pq;
  91     *q++ = v >> 8;
  92     *q++ = v;
  93     *pq = q;
  94 }
  95
  96 static int encode_dvd_subtitles(uint8_t *outbuf, int outbuf_size,
  97                                 const AVSubtitle *h)
  98 {
  99     uint8_t *q, *qq;
 100     int object_id;
 101     int offset1[20], offset2[20];
 102     int i, imax, color, alpha, rects = h->num_rects;
 103     unsigned long hmax;
 104     unsigned long hist[256];
 105     int           cmap[256];
 106
 107     if (rects == 0 || h->rects == NULL)
 108         return -1;
 109     if (rects > 20)
 110         rects = 20;
 111
 112     // analyze bitmaps, compress to 4 colors
 113     for (i=0; i<256; ++i) {
 114         hist[i] = 0;
 115         cmap[i] = 0;
 116     }
 117     for (object_id = 0; object_id < rects; object_id++)
 118         for (i=0; i<h->rects[object_id].w*h->rects[object_id].h; ++i) {
 119             color = h->rects[object_id].bitmap[i];
 120             // only count non-transparent pixels
 121             alpha = h->rects[object_id].rgba_palette[color] >> 24;
 122             hist[color] += alpha;
 123         }
 124     for (color=3;; --color) {
 125         hmax = 0;
 126         imax = 0;
 127         for (i=0; i<256; ++i)
 128             if (hist[i] > hmax) {
 129                 imax = i;
 130                 hmax = hist[i];
 131             }
 132         if (hmax == 0)
 133             break;
 134         if (color == 0)
 135             color = 3;
 136         av_log(NULL, AV_LOG_DEBUG, "dvd_subtitle hist[%d]=%ld -> col %d\n",
 137                imax, hist[imax], color);
 138         cmap[imax] = color;
 139         hist[imax] = 0;
 140     }
 141
 142
 143     // encode data block
 144     q = outbuf + 4;
 145     for (object_id = 0; object_id < rects; object_id++) {
 146         offset1[object_id] = q - outbuf;
 147         // worst case memory requirement: 1 nibble per pixel..
 148         if ((q - outbuf) + h->rects[object_id].w*h->rects[object_id].h/2
 149             + 17*rects + 21 > outbuf_size) {
 150             av_log(NULL, AV_LOG_ERROR, "dvd_subtitle too big\n");
 151             return -1;
 152         }
 153         dvd_encode_rle(&q, h->rects[object_id].bitmap,
 154                        h->rects[object_id].w*2,
 155                        h->rects[object_id].w, h->rects[object_id].h >> 1,
 156                        cmap);
 157         offset2[object_id] = q - outbuf;
 158         dvd_encode_rle(&q, h->rects[object_id].bitmap + h->rects[object_id].w,
 159                        h->rects[object_id].w*2,
 160                        h->rects[object_id].w, h->rects[object_id].h >> 1,
 161                        cmap);
 162     }
 163
 164     // set data packet size
 165     qq = outbuf + 2;
 166     putbe16(&qq, q - outbuf);
 167
 168     // send start display command
 169     putbe16(&q, (h->start_display_time*90) >> 10);
 170     putbe16(&q, (q - outbuf) /*- 2 */ + 8 + 12*rects + 2);
 171     *q++ = 0x03; // palette - 4 nibbles
 172     *q++ = 0x03; *q++ = 0x7f;
 173     *q++ = 0x04; // alpha - 4 nibbles
 174     *q++ = 0xf0; *q++ = 0x00;
 175     //*q++ = 0x0f; *q++ = 0xff;
 176
 177     // XXX not sure if more than one rect can really be encoded..
 178     // 12 bytes per rect
 179     for (object_id = 0; object_id < rects; object_id++) {
 180         int x2 = h->rects[object_id].x + h->rects[object_id].w - 1;
 181         int y2 = h->rects[object_id].y + h->rects[object_id].h - 1;
 182
 183         *q++ = 0x05;
 184         // x1 x2 -> 6 nibbles
 185         *q++ = h->rects[object_id].x >> 4;
 186         *q++ = (h->rects[object_id].x << 4) | ((x2 >> 8) & 0xf);
 187         *q++ = x2;
 188         // y1 y2 -> 6 nibbles
 189         *q++ = h->rects[object_id].y >> 4;
 190         *q++ = (h->rects[object_id].y << 4) | ((y2 >> 8) & 0xf);
 191         *q++ = y2;
 192
 193         *q++ = 0x06;
 194         // offset1, offset2
 195         putbe16(&q, offset1[object_id]);
 196         putbe16(&q, offset2[object_id]);
 197     }
 198     *q++ = 0x01; // start command
 199     *q++ = 0xff; // terminating command
 200
 201     // send stop display command last
 202     putbe16(&q, (h->end_display_time*90) >> 10);
 203     putbe16(&q, (q - outbuf) - 2 /*+ 4*/);
 204     *q++ = 0x02; // set end
 205     *q++ = 0xff; // terminating command
 206
 207     qq = outbuf;
 208     putbe16(&qq, q - outbuf);
 209
 210     av_log(NULL, AV_LOG_DEBUG, "subtitle_packet size=%td\n", q - outbuf);
 211     return q - outbuf;
 212 }
 213
 214 static int dvdsub_init_encoder(AVCodecContext *avctx)
 215 {
 216     return 0;
 217 }
 218
 219 static int dvdsub_close_encoder(AVCodecContext *avctx)
 220 {
 221     return 0;
 222 }
 223
 224 static int dvdsub_encode(AVCodecContext *avctx,
 225                          unsigned char *buf, int buf_size, void *data)
 226 {
 227     //DVDSubtitleContext *s = avctx->priv_data;
 228     AVSubtitle *sub = data;
 229     int ret;
 230
 231     ret = encode_dvd_subtitles(buf, buf_size, sub);
 232     return ret;
 233 }
 234
 235 AVCodec dvdsub_encoder = {
 236     "dvdsub",
 237     CODEC_TYPE_SUBTITLE,
 238     CODEC_ID_DVD_SUBTITLE,
 239     0,
 240     dvdsub_init_encoder,
 241     dvdsub_encode,
 242     dvdsub_close_encoder,
 243 };
 244
 245 /* Local Variables: */
 246 /* c-basic-offset:4 */
 247 /* End: */