libavcodec/dvdsubenc.c

   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)
 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 #if FF_API_AVPICTURE
 112 FF_DISABLE_DEPRECATION_WARNINGS
 113         if (!h->rects[object_id]->data[0]) {
 114             AVSubtitleRect *rect = h->rects[object_id];
 115             int j;
 116             for (j = 0; j < 4; j++) {
 117                 rect->data[j] = rect->pict.data[j];
 118                 rect->linesize[j] = rect->pict.linesize[j];
 119             }
 120         }
 121 FF_ENABLE_DEPRECATION_WARNINGS
 122 #endif
 123
 124         for (i=0; i<h->rects[object_id]->w*h->rects[object_id]->h; ++i) {
 125             color = h->rects[object_id]->data[0][i];
 126             // only count non-transparent pixels
 127             alpha = ((uint32_t *)h->rects[object_id]->data[1])[color] >> 24;
 128             hist[color] += alpha;
 129         }
 130     }
 131     for (color=3;; --color) {
 132         hmax = 0;
 133         imax = 0;
 134         for (i=0; i<256; ++i)
 135             if (hist[i] > hmax) {
 136                 imax = i;
 137                 hmax = hist[i];
 138             }
 139         if (hmax == 0)
 140             break;
 141         if (color == 0)
 142             color = 3;
 143         av_log(NULL, AV_LOG_DEBUG, "dvd_subtitle hist[%d]=%ld -> col %d\n",
 144                imax, hist[imax], color);
 145         cmap[imax] = color;
 146         hist[imax] = 0;
 147     }
 148
 149
 150     // encode data block
 151     q = outbuf + 4;
 152     for (object_id = 0; object_id < rects; object_id++) {
 153         offset1[object_id] = q - outbuf;
 154         // worst case memory requirement: 1 nibble per pixel..
 155         if ((q - outbuf) + h->rects[object_id]->w*h->rects[object_id]->h/2
 156             + 17*rects + 21 > outbuf_size) {
 157             av_log(NULL, AV_LOG_ERROR, "dvd_subtitle too big\n");
 158             return -1;
 159         }
 160         dvd_encode_rle(&q, h->rects[object_id]->data[0],
 161                        h->rects[object_id]->w*2,
 162                        h->rects[object_id]->w, h->rects[object_id]->h >> 1,
 163                        cmap);
 164         offset2[object_id] = q - outbuf;
 165         dvd_encode_rle(&q, h->rects[object_id]->data[0] + h->rects[object_id]->w,
 166                        h->rects[object_id]->w*2,
 167                        h->rects[object_id]->w, h->rects[object_id]->h >> 1,
 168                        cmap);
 169     }
 170
 171     // set data packet size
 172     qq = outbuf + 2;
 173     bytestream_put_be16(&qq, q - outbuf);
 174
 175     // send start display command
 176     bytestream_put_be16(&q, (h->start_display_time*90) >> 10);
 177     bytestream_put_be16(&q, (q - outbuf) /*- 2 */ + 8 + 12*rects + 2);
 178     *q++ = 0x03; // palette - 4 nibbles
 179     *q++ = 0x03; *q++ = 0x7f;
 180     *q++ = 0x04; // alpha - 4 nibbles
 181     *q++ = 0xf0; *q++ = 0x00;
 182     //*q++ = 0x0f; *q++ = 0xff;
 183
 184     // XXX not sure if more than one rect can really be encoded..
 185     // 12 bytes per rect
 186     for (object_id = 0; object_id < rects; object_id++) {
 187         int x2 = h->rects[object_id]->x + h->rects[object_id]->w - 1;
 188         int y2 = h->rects[object_id]->y + h->rects[object_id]->h - 1;
 189
 190         *q++ = 0x05;
 191         // x1 x2 -> 6 nibbles
 192         *q++ = h->rects[object_id]->x >> 4;
 193         *q++ = (h->rects[object_id]->x << 4) | ((x2 >> 8) & 0xf);
 194         *q++ = x2;
 195         // y1 y2 -> 6 nibbles
 196         *q++ = h->rects[object_id]->y >> 4;
 197         *q++ = (h->rects[object_id]->y << 4) | ((y2 >> 8) & 0xf);
 198         *q++ = y2;
 199
 200         *q++ = 0x06;
 201         // offset1, offset2
 202         bytestream_put_be16(&q, offset1[object_id]);
 203         bytestream_put_be16(&q, offset2[object_id]);
 204     }
 205     *q++ = 0x01; // start command
 206     *q++ = 0xff; // terminating command
 207
 208     // send stop display command last
 209     bytestream_put_be16(&q, (h->end_display_time*90) >> 10);
 210     bytestream_put_be16(&q, (q - outbuf) - 2 /*+ 4*/);
 211     *q++ = 0x02; // set end
 212     *q++ = 0xff; // terminating command
 213
 214     qq = outbuf;
 215     bytestream_put_be16(&qq, q - outbuf);
 216
 217     av_log(NULL, AV_LOG_DEBUG, "subtitle_packet size=%td\n", q - outbuf);
 218     return q - outbuf;
 219 }
 220
 221 static int dvdsub_encode(AVCodecContext *avctx,
 222                          unsigned char *buf, int buf_size,
 223                          const AVSubtitle *sub)
 224 {
 225     //DVDSubtitleContext *s = avctx->priv_data;
 226     int ret;
 227
 228     ret = encode_dvd_subtitles(buf, buf_size, sub);
 229     return ret;
 230 }
 231
 232 AVCodec ff_dvdsub_encoder = {
 233     .name           = "dvdsub",
 234     .long_name      = NULL_IF_CONFIG_SMALL("DVD subtitles"),
 235     .type           = AVMEDIA_TYPE_SUBTITLE,
 236     .id             = AV_CODEC_ID_DVD_SUBTITLE,
 237     .encode_sub     = dvdsub_encode,
 238 };