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  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.  * Encode 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.  * Encode 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.         avpriv_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, const AVSubtitle *h)
  115. {
  116.     uint64_t startTime = h->pts / 1000; // FIXME: need better solution...
  117.     uint64_t endTime = startTime + h->end_display_time - h->start_display_time;
  118.     int start_tc[4], end_tc[4];
  119.     uint8_t *hdr = buf + 27; // Point behind the timestamp
  120.     uint8_t *rlelenptr;
  121.     uint16_t width, height;
  122.     int i;
  123.     PutBitContext pb;
  124.  
  125.     if (bufsize < 27 + 7*2 + 4*3) {
  126.         av_log(avctx, AV_LOG_ERROR, "Buffer too small for XSUB header.\n");
  127.         return -1;
  128.     }
  129.  
  130.     // TODO: support multiple rects
  131.     if (h->num_rects != 1)
  132.         av_log(avctx, AV_LOG_WARNING, "Only single rects supported (%d in subtitle.)\n", h->num_rects);
  133.  
  134.     // TODO: render text-based subtitles into bitmaps
  135.     if (!h->rects[0]->pict.data[0] || !h->rects[0]->pict.data[1]) {
  136.         av_log(avctx, AV_LOG_WARNING, "No subtitle bitmap available.\n");
  137.         return -1;
  138.     }
  139.  
  140.     // TODO: color reduction, similar to dvdsub encoder
  141.     if (h->rects[0]->nb_colors > 4)
  142.         av_log(avctx, AV_LOG_WARNING, "No more than 4 subtitle colors supported (%d found.)\n", h->rects[0]->nb_colors);
  143.  
  144.     // TODO: Palette swapping if color zero is not transparent
  145.     if (((uint32_t *)h->rects[0]->pict.data[1])[0] & 0xff)
  146.         av_log(avctx, AV_LOG_WARNING, "Color index 0 is not transparent. Transparency will be messed up.\n");
  147.  
  148.     if (make_tc(startTime, start_tc) || make_tc(endTime, end_tc)) {
  149.         av_log(avctx, AV_LOG_WARNING, "Time code >= 100 hours.\n");
  150.         return -1;
  151.     }
  152.  
  153.     snprintf(buf, 28,
  154.         "[%02d:%02d:%02d.%03d-%02d:%02d:%02d.%03d]",
  155.         start_tc[3], start_tc[2], start_tc[1], start_tc[0],
  156.         end_tc[3],   end_tc[2],   end_tc[1],   end_tc[0]);
  157.  
  158.     // Width and height must probably be multiples of 2.
  159.     // 2 pixels required on either side of subtitle.
  160.     // Possibly due to limitations of hardware renderers.
  161.     // TODO: check if the bitmap is already padded
  162.     width  = FFALIGN(h->rects[0]->w, 2) + PADDING * 2;
  163.     height = FFALIGN(h->rects[0]->h, 2);
  164.  
  165.     bytestream_put_le16(&hdr, width);
  166.     bytestream_put_le16(&hdr, height);
  167.     bytestream_put_le16(&hdr, h->rects[0]->x);
  168.     bytestream_put_le16(&hdr, h->rects[0]->y);
  169.     bytestream_put_le16(&hdr, h->rects[0]->x + width);
  170.     bytestream_put_le16(&hdr, h->rects[0]->y + height);
  171.  
  172.     rlelenptr = hdr; // Will store length of first field here later.
  173.     hdr+=2;
  174.  
  175.     // Palette
  176.     for (i=0; i<4; i++)
  177.         bytestream_put_be24(&hdr, ((uint32_t *)h->rects[0]->pict.data[1])[i]);
  178.  
  179.     // Bitmap
  180.     // RLE buffer. Reserve 2 bytes for possible padding after the last row.
  181.     init_put_bits(&pb, hdr, bufsize - (hdr - buf) - 2);
  182.     if (xsub_encode_rle(&pb, h->rects[0]->pict.data[0],
  183.                         h->rects[0]->pict.linesize[0]*2,
  184.                         h->rects[0]->w, (h->rects[0]->h + 1) >> 1))
  185.         return -1;
  186.     bytestream_put_le16(&rlelenptr, put_bits_count(&pb) >> 3); // Length of first field
  187.  
  188.     if (xsub_encode_rle(&pb, h->rects[0]->pict.data[0] + h->rects[0]->pict.linesize[0],
  189.                         h->rects[0]->pict.linesize[0]*2,
  190.                         h->rects[0]->w, h->rects[0]->h >> 1))
  191.         return -1;
  192.  
  193.     // Enforce total height to be a multiple of 2
  194.     if (h->rects[0]->h & 1) {
  195.         put_xsub_rle(&pb, h->rects[0]->w, PADDING_COLOR);
  196.         avpriv_align_put_bits(&pb);
  197.     }
  198.  
  199.     flush_put_bits(&pb);
  200.  
  201.     return hdr - buf + put_bits_count(&pb)/8;
  202. }
  203.  
  204. static av_cold int xsub_encoder_init(AVCodecContext *avctx)
  205. {
  206.     if (!avctx->codec_tag)
  207.         avctx->codec_tag = MKTAG('D','X','S','B');
  208.  
  209.     return 0;
  210. }
  211.  
  212. AVCodec ff_xsub_encoder = {
  213.     .name       = "xsub",
  214.     .long_name  = NULL_IF_CONFIG_SMALL("DivX subtitles (XSUB)"),
  215.     .type       = AVMEDIA_TYPE_SUBTITLE,
  216.     .id         = AV_CODEC_ID_XSUB,
  217.     .init       = xsub_encoder_init,
  218.     .encode_sub = xsub_encode,
  219. };
  220.