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  1. /*
  2.  * XSUB subtitle decoder
  3.  * Copyright (c) 2007 Reimar Döffinger
  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.  
  22. #include "libavutil/mathematics.h"
  23. #include "libavutil/imgutils.h"
  24. #include "avcodec.h"
  25. #include "get_bits.h"
  26. #include "bytestream.h"
  27.  
  28. static av_cold int decode_init(AVCodecContext *avctx) {
  29.     avctx->pix_fmt = AV_PIX_FMT_PAL8;
  30.     return 0;
  31. }
  32.  
  33. static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
  34. static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
  35.  
  36. static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time) {
  37.     int i;
  38.     int64_t ms = 0;
  39.     if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
  40.         return AV_NOPTS_VALUE;
  41.     for (i = 0; i < sizeof(tc_offsets); i++) {
  42.         uint8_t c = buf[tc_offsets[i]] - '0';
  43.         if (c > 9) return AV_NOPTS_VALUE;
  44.         ms = (ms + c) * tc_muls[i];
  45.     }
  46.     return ms - packet_time;
  47. }
  48.  
  49. static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
  50.                         AVPacket *avpkt) {
  51.     const uint8_t *buf = avpkt->data;
  52.     int buf_size = avpkt->size;
  53.     AVSubtitle *sub = data;
  54.     const uint8_t *buf_end = buf + buf_size;
  55.     uint8_t *bitmap;
  56.     int w, h, x, y, i;
  57.     int64_t packet_time = 0;
  58.     GetBitContext gb;
  59.     int has_alpha = avctx->codec_tag == MKTAG('D','X','S','A');
  60.  
  61.     // check that at least header fits
  62.     if (buf_size < 27 + 7 * 2 + 4 * 3) {
  63.         av_log(avctx, AV_LOG_ERROR, "coded frame size %d too small\n", buf_size);
  64.         return -1;
  65.     }
  66.  
  67.     // read start and end time
  68.     if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
  69.         av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
  70.         return -1;
  71.     }
  72.     if (avpkt->pts != AV_NOPTS_VALUE)
  73.         packet_time = av_rescale_q(avpkt->pts, AV_TIME_BASE_Q, (AVRational){1, 1000});
  74.     sub->start_display_time = parse_timecode(buf +  1, packet_time);
  75.     sub->end_display_time   = parse_timecode(buf + 14, packet_time);
  76.     buf += 27;
  77.  
  78.     // read header
  79.     w = bytestream_get_le16(&buf);
  80.     h = bytestream_get_le16(&buf);
  81.     if (av_image_check_size(w, h, 0, avctx) < 0)
  82.         return -1;
  83.     x = bytestream_get_le16(&buf);
  84.     y = bytestream_get_le16(&buf);
  85.     // skip bottom right position, it gives no new information
  86.     bytestream_get_le16(&buf);
  87.     bytestream_get_le16(&buf);
  88.     // The following value is supposed to indicate the start offset
  89.     // (relative to the palette) of the data for the second field,
  90.     // however there are files in which it has a bogus value and thus
  91.     // we just ignore it
  92.     bytestream_get_le16(&buf);
  93.  
  94.     // allocate sub and set values
  95.     sub->rects =  av_mallocz(sizeof(*sub->rects));
  96.     sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
  97.     sub->num_rects = 1;
  98.     sub->rects[0]->x = x; sub->rects[0]->y = y;
  99.     sub->rects[0]->w = w; sub->rects[0]->h = h;
  100.     sub->rects[0]->type = SUBTITLE_BITMAP;
  101.     sub->rects[0]->pict.linesize[0] = w;
  102.     sub->rects[0]->pict.data[0] = av_malloc(w * h);
  103.     sub->rects[0]->nb_colors = 4;
  104.     sub->rects[0]->pict.data[1] = av_mallocz(AVPALETTE_SIZE);
  105.  
  106.     // read palette
  107.     for (i = 0; i < sub->rects[0]->nb_colors; i++)
  108.         ((uint32_t*)sub->rects[0]->pict.data[1])[i] = bytestream_get_be24(&buf);
  109.     // make all except background (first entry) non-transparent
  110.     for (i = 0; i < sub->rects[0]->nb_colors; i++)
  111.         ((uint32_t*)sub->rects[0]->pict.data[1])[i] |= (has_alpha ? *buf++ : (i ? 0xff : 0)) << 24;
  112.  
  113.     // process RLE-compressed data
  114.     init_get_bits(&gb, buf, (buf_end - buf) * 8);
  115.     bitmap = sub->rects[0]->pict.data[0];
  116.     for (y = 0; y < h; y++) {
  117.         // interlaced: do odd lines
  118.         if (y == (h + 1) / 2) bitmap = sub->rects[0]->pict.data[0] + w;
  119.         for (x = 0; x < w; ) {
  120.             int log2 = ff_log2_tab[show_bits(&gb, 8)];
  121.             int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
  122.             int color = get_bits(&gb, 2);
  123.             run = FFMIN(run, w - x);
  124.             // run length 0 means till end of row
  125.             if (!run) run = w - x;
  126.             memset(bitmap, color, run);
  127.             bitmap += run;
  128.             x += run;
  129.         }
  130.         // interlaced, skip every second line
  131.         bitmap += w;
  132.         align_get_bits(&gb);
  133.     }
  134.     *data_size = 1;
  135.     return buf_size;
  136. }
  137.  
  138. AVCodec ff_xsub_decoder = {
  139.     .name      = "xsub",
  140.     .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
  141.     .type      = AVMEDIA_TYPE_SUBTITLE,
  142.     .id        = AV_CODEC_ID_XSUB,
  143.     .init      = decode_init,
  144.     .decode    = decode_frame,
  145. };
  146.