libavcodec/dvdsubenc.c

   1 /*
   2  * DVD subtitle encoding for ffmpeg
   3  * Copyright (c) 2005 Wolfram Gloger.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  18  */
  19 #include "avcodec.h"
  20
  21 #undef NDEBUG
  22 #include <assert.h>
  23
  24 typedef struct DVDSubtitleContext {
  25 } DVDSubtitleContext;
  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 inline void putbe16(uint8_t **pq, uint16_t v)
  90 {
  91     uint8_t *q = *pq;
  92     *q++ = v >> 8;
  93     *q++ = v;
  94     *pq = q;
  95 }
  96
  97 static int encode_dvd_subtitles(uint8_t *outbuf, int outbuf_size,
  98                                 const AVSubtitle *h)
  99 {
 100     uint8_t *q, *qq;
 101     int object_id;
 102     int offset1[20], offset2[20];
 103     int i, imax, color, alpha, rects = h->num_rects;
 104     unsigned long hmax;
 105     unsigned long hist[256];
 106     int           cmap[256];
 107
 108     if (rects == 0 || h->rects == NULL)
 109         return -1;
 110     if (rects > 20)
 111         rects = 20;
 112
 113     // analyze bitmaps, compress to 4 colors
 114     for (i=0; i<256; ++i) {
 115         hist[i] = 0;
 116         cmap[i] = 0;
 117     }
 118     for (object_id = 0; object_id < rects; object_id++)
 119         for (i=0; i<h->rects[object_id].w*h->rects[object_id].h; ++i) {
 120             color = h->rects[object_id].bitmap[i];
 121             // only count non-transparent pixels
 122             alpha = h->rects[object_id].rgba_palette[color] >> 24;
 123             hist[color] += alpha;
 124         }
 125     for (color=3;; --color) {
 126         hmax = 0;
 127         imax = 0;
 128         for (i=0; i<256; ++i)
 129             if (hist[i] > hmax) {
 130                 imax = i;
 131                 hmax = hist[i];
 132             }
 133         if (hmax == 0)
 134             break;
 135         if (color == 0)
 136             color = 3;
 137         av_log(NULL, AV_LOG_DEBUG, "dvd_subtitle hist[%d]=%ld -> col %d\n",
 138                imax, hist[imax], color);
 139         cmap[imax] = color;
 140         hist[imax] = 0;
 141     }
 142
 143
 144     // encode data block
 145     q = outbuf + 4;
 146     for (object_id = 0; object_id < rects; object_id++) {
 147         offset1[object_id] = q - outbuf;
 148         // worst case memory requirement: 1 nibble per pixel..
 149         if ((q - outbuf) + h->rects[object_id].w*h->rects[object_id].h/2
 150             + 17*rects + 21 > outbuf_size) {
 151             av_log(NULL, AV_LOG_ERROR, "dvd_subtitle too big\n");
 152             return -1;
 153         }
 154         dvd_encode_rle(&q, h->rects[object_id].bitmap,
 155                        h->rects[object_id].w*2,
 156                        h->rects[object_id].w, h->rects[object_id].h >> 1,
 157                        cmap);
 158         offset2[object_id] = q - outbuf;
 159         dvd_encode_rle(&q, h->rects[object_id].bitmap + h->rects[object_id].w,
 160                        h->rects[object_id].w*2,
 161                        h->rects[object_id].w, h->rects[object_id].h >> 1,
 162                        cmap);
 163     }
 164
 165     // set data packet size
 166     qq = outbuf + 2;
 167     putbe16(&qq, q - outbuf);
 168
 169     // send start display command
 170     putbe16(&q, (h->start_display_time*90) >> 10);
 171     putbe16(&q, (q - outbuf) /*- 2 */ + 8 + 12*rects + 2);
 172     *q++ = 0x03; // palette - 4 nibbles
 173     *q++ = 0x03; *q++ = 0x7f;
 174     *q++ = 0x04; // alpha - 4 nibbles
 175     *q++ = 0xf0; *q++ = 0x00;
 176     //*q++ = 0x0f; *q++ = 0xff;
 177
 178     // XXX not sure if more than one rect can really be encoded..
 179     // 12 bytes per rect
 180     for (object_id = 0; object_id < rects; object_id++) {
 181         int x2 = h->rects[object_id].x + h->rects[object_id].w - 1;
 182         int y2 = h->rects[object_id].y + h->rects[object_id].h - 1;
 183
 184         *q++ = 0x05;
 185         // x1 x2 -> 6 nibbles
 186         *q++ = h->rects[object_id].x >> 4;
 187         *q++ = (h->rects[object_id].x << 4) | ((x2 >> 8) & 0xf);
 188         *q++ = x2;
 189         // y1 y2 -> 6 nibbles
 190         *q++ = h->rects[object_id].y >> 4;
 191         *q++ = (h->rects[object_id].y << 4) | ((y2 >> 8) & 0xf);
 192         *q++ = y2;
 193
 194         *q++ = 0x06;
 195         // offset1, offset2
 196         putbe16(&q, offset1[object_id]);
 197         putbe16(&q, offset2[object_id]);
 198     }
 199     *q++ = 0x01; // start command
 200     *q++ = 0xff; // terminating command
 201
 202     // send stop display command last
 203     putbe16(&q, (h->end_display_time*90) >> 10);
 204     putbe16(&q, (q - outbuf) - 2 /*+ 4*/);
 205     *q++ = 0x02; // set end
 206     *q++ = 0xff; // terminating command
 207
 208     qq = outbuf;
 209     putbe16(&qq, q - outbuf);
 210
 211     av_log(NULL, AV_LOG_DEBUG, "subtitle_packet size=%td\n", q - outbuf);
 212     return q - outbuf;
 213 }
 214
 215 static int dvdsub_init_encoder(AVCodecContext *avctx)
 216 {
 217     return 0;
 218 }
 219
 220 static int dvdsub_close_encoder(AVCodecContext *avctx)
 221 {
 222     return 0;
 223 }
 224
 225 static int dvdsub_encode(AVCodecContext *avctx,
 226                          unsigned char *buf, int buf_size, void *data)
 227 {
 228     //DVDSubtitleContext *s = avctx->priv_data;
 229     AVSubtitle *sub = data;
 230     int ret;
 231
 232     ret = encode_dvd_subtitles(buf, buf_size, sub);
 233     return ret;
 234 }
 235
 236 AVCodec dvdsub_encoder = {
 237     "dvdsub",
 238     CODEC_TYPE_SUBTITLE,
 239     CODEC_ID_DVD_SUBTITLE,
 240     sizeof(DVDSubtitleContext),
 241     dvdsub_init_encoder,
 242     dvdsub_encode,
 243     dvdsub_close_encoder,
 244 };
 245
 246 /* Local Variables: */
 247 /* c-basic-offset:4 */
 248 /* End: */