libavcodec/xsubenc.c

   1 /*
   2  * DivX (XSUB) subtitle encoder
   3  * Copyright (c) 2005 DivX, Inc.
   4  * Copyright (c) 2009 Bjorn Axelsson
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include "avcodec.h"
  24 #include "bytestream.h"
  25 #include "put_bits.h"
  26
  27 /**
  28  * Number of pixels to pad left and right.
  29  *
  30  * The official encoder pads the subtitles with two pixels on either side,
  31  * but until we find out why, we won't do it (we will pad to have width
  32  * divisible by 2 though).
  33  */
  34 #define PADDING 0
  35 #define PADDING_COLOR 0
  36
  37 /**
  38  * Encodes a single color run. At most 16 bits will be used.
  39  * \param len   length of the run, values > 255 mean "until end of line", may not be < 0.
  40  * \param color color to encode, only the lowest two bits are used and all others must be 0.
  41  */
  42 static void put_xsub_rle(PutBitContext *pb, int len, int color)
  43 {
  44     if (len <= 255)
  45         put_bits(pb, 2 + ((ff_log2_tab[len] >> 1) << 2), len);
  46     else
  47         put_bits(pb, 14, 0);
  48     put_bits(pb, 2, color);
  49 }
  50
  51 /**
  52  * Encodes a 4-color bitmap with XSUB rle.
  53  *
  54  * The encoded bitmap may be wider than the source bitmap due to padding.
  55  */
  56 static int xsub_encode_rle(PutBitContext *pb, const uint8_t *bitmap,
  57                            int linesize, int w, int h)
  58 {
  59     int x0, x1, y, len, color = PADDING_COLOR;
  60
  61     for (y = 0; y < h; y++) {
  62         x0 = 0;
  63         while (x0 < w) {
  64             // Make sure we have enough room for at least one run and padding
  65             if (pb->size_in_bits - put_bits_count(pb) < 7*8)
  66                 return -1;
  67
  68             x1 = x0;
  69             color = bitmap[x1++] & 3;
  70             while (x1 < w && (bitmap[x1] & 3) == color)
  71                 x1++;
  72             len = x1 - x0;
  73             if (PADDING && x0 == 0) {
  74                 if (color == PADDING_COLOR) {
  75                     len += PADDING;
  76                     x0  -= PADDING;
  77                 } else
  78                     put_xsub_rle(pb, PADDING, PADDING_COLOR);
  79             }
  80
  81             // Run can't be longer than 255, unless it is the rest of a row
  82             if (x1 == w && color == PADDING_COLOR) {
  83                 len += PADDING + (w&1);
  84             } else
  85                 len = FFMIN(len, 255);
  86             put_xsub_rle(pb, len, color);
  87
  88             x0 += len;
  89         }
  90         if (color != PADDING_COLOR && (PADDING + (w&1)))
  91             put_xsub_rle(pb, PADDING + (w&1), PADDING_COLOR);
  92
  93         align_put_bits(pb);
  94
  95         bitmap += linesize;
  96     }
  97
  98     return 0;
  99 }
 100
 101 static int make_tc(uint64_t ms, int *tc)
 102 {
 103     static const int tc_divs[3] = { 1000, 60, 60 };
 104     int i;
 105     for (i=0; i<3; i++) {
 106         tc[i] = ms % tc_divs[i];
 107         ms /= tc_divs[i];
 108     }
 109     tc[3] = ms;
 110     return ms > 99;
 111 }
 112
 113 static int xsub_encode(AVCodecContext *avctx, unsigned char *buf,
 114                        int bufsize, void *data)
 115 {
 116     AVSubtitle *h = data;
 117     uint64_t startTime = h->pts / 1000; // FIXME: need better solution...
 118     uint64_t endTime = startTime + h->end_display_time - h->start_display_time;
 119     int start_tc[4], end_tc[4];
 120     uint8_t *hdr = buf + 27; // Point behind the timestamp
 121     uint8_t *rlelenptr;
 122     uint16_t width, height;
 123     int i;
 124     PutBitContext pb;
 125
 126     if (bufsize < 27 + 7*2 + 4*3) {
 127         av_log(avctx, AV_LOG_ERROR, "Buffer too small for XSUB header.\n");
 128         return -1;
 129     }
 130
 131     // TODO: support multiple rects
 132     if (h->num_rects > 1)
 133         av_log(avctx, AV_LOG_WARNING, "Only single rects supported (%d in subtitle.)\n", h->num_rects);
 134
 135     // TODO: render text-based subtitles into bitmaps
 136     if (!h->rects[0]->pict.data[0] || !h->rects[0]->pict.data[1]) {
 137         av_log(avctx, AV_LOG_WARNING, "No subtitle bitmap available.\n");
 138         return -1;
 139     }
 140
 141     // TODO: color reduction, similar to dvdsub encoder
 142     if (h->rects[0]->nb_colors > 4)
 143         av_log(avctx, AV_LOG_WARNING, "No more than 4 subtitle colors supported (%d found.)\n", h->rects[0]->nb_colors);
 144
 145     // TODO: Palette swapping if color zero is not transparent
 146     if (((uint32_t *)h->rects[0]->pict.data[1])[0] & 0xff)
 147         av_log(avctx, AV_LOG_WARNING, "Color index 0 is not transparent. Transparency will be messed up.\n");
 148
 149     if (make_tc(startTime, start_tc) || make_tc(endTime, end_tc)) {
 150         av_log(avctx, AV_LOG_WARNING, "Time code >= 100 hours.\n");
 151         return -1;
 152     }
 153
 154     snprintf(buf, 28,
 155         "[%02d:%02d:%02d.%03d-%02d:%02d:%02d.%03d]",
 156         start_tc[3], start_tc[2], start_tc[1], start_tc[0],
 157         end_tc[3],   end_tc[2],   end_tc[1],   end_tc[0]);
 158
 159     // Width and height must probably be multiples of 2.
 160     // 2 pixels required on either side of subtitle.
 161     // Possibly due to limitations of hardware renderers.
 162     // TODO: check if the bitmap is already padded
 163     width  = FFALIGN(h->rects[0]->w, 2) + PADDING * 2;
 164     height = FFALIGN(h->rects[0]->h, 2);
 165
 166     bytestream_put_le16(&hdr, width);
 167     bytestream_put_le16(&hdr, height);
 168     bytestream_put_le16(&hdr, h->rects[0]->x);
 169     bytestream_put_le16(&hdr, h->rects[0]->y);
 170     bytestream_put_le16(&hdr, h->rects[0]->x + width);
 171     bytestream_put_le16(&hdr, h->rects[0]->y + height);
 172
 173     rlelenptr = hdr; // Will store length of first field here later.
 174     hdr+=2;
 175
 176     // Palette
 177     for (i=0; i<4; i++)
 178         bytestream_put_be24(&hdr, ((uint32_t *)h->rects[0]->pict.data[1])[i]);
 179
 180     // Bitmap
 181     // RLE buffer. Reserve 2 bytes for possible padding after the last row.
 182     init_put_bits(&pb, hdr, bufsize - (hdr - buf) - 2);
 183     if (xsub_encode_rle(&pb, h->rects[0]->pict.data[0],
 184                         h->rects[0]->pict.linesize[0]*2,
 185                         h->rects[0]->w, (h->rects[0]->h + 1) >> 1))
 186         return -1;
 187     bytestream_put_le16(&rlelenptr, put_bits_count(&pb) >> 3); // Length of first field
 188
 189     if (xsub_encode_rle(&pb, h->rects[0]->pict.data[0] + h->rects[0]->pict.linesize[0],
 190                         h->rects[0]->pict.linesize[0]*2,
 191                         h->rects[0]->w, h->rects[0]->h >> 1))
 192         return -1;
 193
 194     // Enforce total height to be be multiple of 2
 195     if (h->rects[0]->h & 1) {
 196         put_xsub_rle(&pb, h->rects[0]->w, PADDING_COLOR);
 197         align_put_bits(&pb);
 198     }
 199
 200     flush_put_bits(&pb);
 201
 202     return hdr - buf + put_bits_count(&pb)/8;
 203 }
 204
 205 static av_cold int xsub_encoder_init(AVCodecContext *avctx)
 206 {
 207     if (!avctx->codec_tag)
 208         avctx->codec_tag = MKTAG('D','X','S','B');
 209
 210     return 0;
 211 }
 212
 213 AVCodec xsub_encoder = {
 214     "xsub",
 215     CODEC_TYPE_SUBTITLE,
 216     CODEC_ID_XSUB,
 217     0,
 218     xsub_encoder_init,
 219     xsub_encode,
 220     NULL,
 221     .long_name = NULL_IF_CONFIG_SMALL("DivX subtitles (XSUB)"),
 222 };