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ffmpeg-4.2.2/libavcodec/srtdec.c 3.96 KB
aac5773f   hucm   功能基本完成,接口待打磨
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  /*
   * SubRip subtitle decoder
   * Copyright (c) 2010  Aurelien Jacobs <aurel@gnuage.org>
   *
   * 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 "libavutil/avstring.h"
  #include "libavutil/common.h"
  #include "libavutil/intreadwrite.h"
  #include "libavutil/parseutils.h"
  #include "avcodec.h"
  #include "ass.h"
  #include "htmlsubtitles.h"
  
  static int srt_to_ass(AVCodecContext *avctx, AVBPrint *dst,
                         const char *in, int x1, int y1, int x2, int y2)
  {
      if (x1 >= 0 && y1 >= 0) {
          /* XXX: here we rescale coordinate assuming they are in DVD resolution
           * (720x480) since we don't have anything better */
  
          if (x2 >= 0 && y2 >= 0 && (x2 != x1 || y2 != y1) && x2 >= x1 && y2 >= y1) {
              /* text rectangle defined, write the text at the center of the rectangle */
              const int cx = x1 + (x2 - x1)/2;
              const int cy = y1 + (y2 - y1)/2;
              const int scaled_x = cx * (int64_t)ASS_DEFAULT_PLAYRESX / 720;
              const int scaled_y = cy * (int64_t)ASS_DEFAULT_PLAYRESY / 480;
              av_bprintf(dst, "{\\an5}{\\pos(%d,%d)}", scaled_x, scaled_y);
          } else {
              /* only the top left corner, assume the text starts in that corner */
              const int scaled_x = x1 * (int64_t)ASS_DEFAULT_PLAYRESX / 720;
              const int scaled_y = y1 * (int64_t)ASS_DEFAULT_PLAYRESY / 480;
              av_bprintf(dst, "{\\an1}{\\pos(%d,%d)}", scaled_x, scaled_y);
          }
      }
  
      return ff_htmlmarkup_to_ass(avctx, dst, in);
  }
  
  static int srt_decode_frame(AVCodecContext *avctx,
                              void *data, int *got_sub_ptr, AVPacket *avpkt)
  {
      AVSubtitle *sub = data;
      AVBPrint buffer;
      int x1 = -1, y1 = -1, x2 = -1, y2 = -1;
      int size, ret;
      const uint8_t *p = av_packet_get_side_data(avpkt, AV_PKT_DATA_SUBTITLE_POSITION, &size);
      FFASSDecoderContext *s = avctx->priv_data;
  
      if (p && size == 16) {
          x1 = AV_RL32(p     );
          y1 = AV_RL32(p +  4);
          x2 = AV_RL32(p +  8);
          y2 = AV_RL32(p + 12);
      }
  
      if (avpkt->size <= 0)
          return avpkt->size;
  
      av_bprint_init(&buffer, 0, AV_BPRINT_SIZE_UNLIMITED);
  
      ret = srt_to_ass(avctx, &buffer, avpkt->data, x1, y1, x2, y2);
      if (ret >= 0)
          ret = ff_ass_add_rect(sub, buffer.str, s->readorder++, 0, NULL, NULL);
      av_bprint_finalize(&buffer, NULL);
      if (ret < 0)
          return ret;
  
      *got_sub_ptr = sub->num_rects > 0;
      return avpkt->size;
  }
  
  #if CONFIG_SRT_DECODER
  /* deprecated decoder */
  AVCodec ff_srt_decoder = {
      .name         = "srt",
      .long_name    = NULL_IF_CONFIG_SMALL("SubRip subtitle"),
      .type         = AVMEDIA_TYPE_SUBTITLE,
      .id           = AV_CODEC_ID_SUBRIP,
      .init         = ff_ass_subtitle_header_default,
      .decode       = srt_decode_frame,
      .flush        = ff_ass_decoder_flush,
      .priv_data_size = sizeof(FFASSDecoderContext),
  };
  #endif
  
  #if CONFIG_SUBRIP_DECODER
  AVCodec ff_subrip_decoder = {
      .name         = "subrip",
      .long_name    = NULL_IF_CONFIG_SMALL("SubRip subtitle"),
      .type         = AVMEDIA_TYPE_SUBTITLE,
      .id           = AV_CODEC_ID_SUBRIP,
      .init         = ff_ass_subtitle_header_default,
      .decode       = srt_decode_frame,
      .flush        = ff_ass_decoder_flush,
      .priv_data_size = sizeof(FFASSDecoderContext),
  };
  #endif