text: /*
   * XSUB subtitle decoder
   * Copyright (c) 2007 Reimar Döffinger
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  #include "avcodec.h"
  #include "bitstream.h"
  #include "bytestream.h"
  
  static av_cold int decode_init(AVCodecContext *avctx) {
      avctx->pix_fmt = PIX_FMT_PAL8;
      return 0;
  }
  
  static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
  static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
  
  static uint64_t parse_timecode(const uint8_t *buf) {
      int i;
      int64_t ms = 0;
      if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
          return AV_NOPTS_VALUE;
      for (i = 0; i < sizeof(tc_offsets); i++) {
          uint8_t c = buf[tc_offsets[i]] - '0';
          if (c > 9) return AV_NOPTS_VALUE;
          ms = (ms + c) * tc_muls[i];
      }
      return ms;
  }
  
  static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
                          const uint8_t *buf, int buf_size) {
      AVSubtitle *sub = data;
      const uint8_t *buf_end = buf + buf_size;
      uint8_t *bitmap;
      int w, h, x, y, rlelen, i;
      GetBitContext gb;
  
      sub->format = 0;
  
      // check that at least header fits
      if (buf_size < 27 + 7 * 2 + 4 * 3) {
          av_log(avctx, AV_LOG_ERROR, "coded frame too small\n");
          return -1;
      }
  
      // read start and end time
      if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
          av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
          return -1;
      }
      sub->start_display_time = parse_timecode(buf +  1);
      sub->end_display_time   = parse_timecode(buf + 14);
      buf += 27;
  
      // read header
      w = bytestream_get_le16(&buf);
      h = bytestream_get_le16(&buf);
      if (avcodec_check_dimensions(avctx, w, h) < 0)
          return -1;
      x = bytestream_get_le16(&buf);
      y = bytestream_get_le16(&buf);
      // skip bottom right position, it gives no new information
      bytestream_get_le16(&buf);
      bytestream_get_le16(&buf);
      rlelen = bytestream_get_le16(&buf);
  
      // allocate sub and set values
      if (!sub->rects) {
          sub->rects =  av_mallocz(sizeof(*sub->rects));
          sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
          sub->num_rects = 1;
      }
      av_freep(&sub->rects[0]->pict.data[0]);
      sub->rects[0]->x = x; sub->rects[0]->y = y;
      sub->rects[0]->w = w; sub->rects[0]->h = h;
      sub->rects[0]->pict.linesize[0] = w;
      sub->rects[0]->pict.data[0] = av_malloc(w * h);
      sub->rects[0]->nb_colors = 4;
      sub->rects[0]->pict.data[1] = av_malloc(sub->rects[0]->nb_colors * 4);
  
      // read palette
      for (i = 0; i < sub->rects[0]->nb_colors; i++)
          ((uint32_t*)sub->rects[0]->pict.data[1])[i] = bytestream_get_be24(&buf);
      // make all except background (first entry) non-transparent
      for (i = 1; i < sub->rects[0]->nb_colors; i++)
          ((uint32_t*)sub->rects[0]->pict.data[1])[i] |= 0xff000000;
  
      // process RLE-compressed data
      rlelen = FFMIN(rlelen, buf_end - buf);
      init_get_bits(&gb, buf, rlelen * 8);
      bitmap = sub->rects[0]->pict.data[0];
      for (y = 0; y < h; y++) {
          // interlaced: do odd lines
          if (y == (h + 1) / 2) bitmap = sub->rects[0]->pict.data[0] + w;
          for (x = 0; x < w; ) {
              int log2 = ff_log2_tab[show_bits(&gb, 8)];
              int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
              int color = get_bits(&gb, 2);
              run = FFMIN(run, w - x);
              // run length 0 means till end of row
              if (!run) run = w - x;
              memset(bitmap, color, run);
              bitmap += run;
              x += run;
          }
          // interlaced, skip every second line
          bitmap += w;
          align_get_bits(&gb);
      }
      *data_size = 1;
      return buf_size;
  }
  
  AVCodec xsub_decoder = {
      "xsub",
      CODEC_TYPE_SUBTITLE,
      CODEC_ID_XSUB,
      0,
      decode_init,
      NULL,
      NULL,
      decode_frame,
      .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
  };
  