git.sesse.net Git - ffmpeg/blob - libavcodec/dvdsubenc.c

   1 /*
   2  * DVD subtitle encoding
   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 #include "bytestream.h"
  23 #include "libavutil/avassert.h"
  24
  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             av_assert0(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 int encode_dvd_subtitles(uint8_t *outbuf, int outbuf_size,
  89                                 const AVSubtitle *h)
  90 {
  91     uint8_t *q, *qq;
  92     int object_id;
  93     int offset1[20], offset2[20];
  94     int i, imax, color, alpha, rects = h->num_rects;
  95     unsigned long hmax;
  96     unsigned long hist[256];
  97     int           cmap[256];
  98
  99     if (rects == 0 || h->rects == NULL)
 100         return -1;
 101     if (rects > 20)
 102         rects = 20;
 103
 104     // analyze bitmaps, compress to 4 colors
 105     for (i=0; i<256; ++i) {
 106         hist[i] = 0;
 107         cmap[i] = 0;
 108     }
 109     for (object_id = 0; object_id < rects; object_id++)
 110         for (i=0; i<h->rects[object_id]->w*h->rects[object_id]->h; ++i) {
 111             color = h->rects[object_id]->pict.data[0][i];
 112             // only count non-transparent pixels
 113             alpha = ((uint32_t*)h->rects[object_id]->pict.data[1])[color] >> 24;
 114             hist[color] += alpha;
 115         }
 116     for (color=3;; --color) {
 117         hmax = 0;
 118         imax = 0;
 119         for (i=0; i<256; ++i)
 120             if (hist[i] > hmax) {
 121                 imax = i;
 122                 hmax = hist[i];
 123             }
 124         if (hmax == 0)
 125             break;
 126         if (color == 0)
 127             color = 3;
 128         av_log(NULL, AV_LOG_DEBUG, "dvd_subtitle hist[%d]=%ld -> col %d\n",
 129                imax, hist[imax], color);
 130         cmap[imax] = color;
 131         hist[imax] = 0;
 132     }
 133
 134
 135     // encode data block
 136     q = outbuf + 4;
 137     for (object_id = 0; object_id < rects; object_id++) {
 138         offset1[object_id] = q - outbuf;
 139         // worst case memory requirement: 1 nibble per pixel..
 140         if ((q - outbuf) + h->rects[object_id]->w*h->rects[object_id]->h/2
 141             + 17*rects + 21 > outbuf_size) {
 142             av_log(NULL, AV_LOG_ERROR, "dvd_subtitle too big\n");
 143             return -1;
 144         }
 145         dvd_encode_rle(&q, h->rects[object_id]->pict.data[0],
 146                        h->rects[object_id]->w*2,
 147                        h->rects[object_id]->w, h->rects[object_id]->h >> 1,
 148                        cmap);
 149         offset2[object_id] = q - outbuf;
 150         dvd_encode_rle(&q, h->rects[object_id]->pict.data[0] + h->rects[object_id]->w,
 151                        h->rects[object_id]->w*2,
 152                        h->rects[object_id]->w, h->rects[object_id]->h >> 1,
 153                        cmap);
 154     }
 155
 156     // set data packet size
 157     qq = outbuf + 2;
 158     bytestream_put_be16(&qq, q - outbuf);
 159
 160     // send start display command
 161     bytestream_put_be16(&q, (h->start_display_time*90) >> 10);
 162     bytestream_put_be16(&q, (q - outbuf) /*- 2 */ + 8 + 12*rects + 2);
 163     *q++ = 0x03; // palette - 4 nibbles
 164     *q++ = 0x03; *q++ = 0x7f;
 165     *q++ = 0x04; // alpha - 4 nibbles
 166     *q++ = 0xf0; *q++ = 0x00;
 167     //*q++ = 0x0f; *q++ = 0xff;
 168
 169     // XXX not sure if more than one rect can really be encoded..
 170     // 12 bytes per rect
 171     for (object_id = 0; object_id < rects; object_id++) {
 172         int x2 = h->rects[object_id]->x + h->rects[object_id]->w - 1;
 173         int y2 = h->rects[object_id]->y + h->rects[object_id]->h - 1;
 174
 175         *q++ = 0x05;
 176         // x1 x2 -> 6 nibbles
 177         *q++ = h->rects[object_id]->x >> 4;
 178         *q++ = (h->rects[object_id]->x << 4) | ((x2 >> 8) & 0xf);
 179         *q++ = x2;
 180         // y1 y2 -> 6 nibbles
 181         *q++ = h->rects[object_id]->y >> 4;
 182         *q++ = (h->rects[object_id]->y << 4) | ((y2 >> 8) & 0xf);
 183         *q++ = y2;
 184
 185         *q++ = 0x06;
 186         // offset1, offset2
 187         bytestream_put_be16(&q, offset1[object_id]);
 188         bytestream_put_be16(&q, offset2[object_id]);
 189     }
 190     *q++ = 0x01; // start command
 191     *q++ = 0xff; // terminating command
 192
 193     // send stop display command last
 194     bytestream_put_be16(&q, (h->end_display_time*90) >> 10);
 195     bytestream_put_be16(&q, (q - outbuf) - 2 /*+ 4*/);
 196     *q++ = 0x02; // set end
 197     *q++ = 0xff; // terminating command
 198
 199     qq = outbuf;
 200     bytestream_put_be16(&qq, q - outbuf);
 201
 202     av_log(NULL, AV_LOG_DEBUG, "subtitle_packet size=%td\n", q - outbuf);
 203     return q - outbuf;
 204 }
 205
 206 static int dvdsub_encode(AVCodecContext *avctx,
 207                          unsigned char *buf, int buf_size, void *data)
 208 {
 209     //DVDSubtitleContext *s = avctx->priv_data;
 210     AVSubtitle *sub = data;
 211     int ret;
 212
 213     ret = encode_dvd_subtitles(buf, buf_size, sub);
 214     return ret;
 215 }
 216
 217 AVCodec ff_dvdsub_encoder = {
 218     .name           = "dvdsub",
 219     .type           = AVMEDIA_TYPE_SUBTITLE,
 220     .id             = AV_CODEC_ID_DVD_SUBTITLE,
 221     .encode         = dvdsub_encode,
 222     .long_name      = NULL_IF_CONFIG_SMALL("DVD subtitles"),
 223 };