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ffmpeg-4.2.2/libavformat/webvttenc.c 2.98 KB
aac5773f   hucm   功能基本完成,接口待打磨
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  /*
   * Copyright (c) 2013 Matthew Heaney
   *
   * 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
   */
  
  /**
   * @file
   * WebVTT subtitle muxer
   * @see http://dev.w3.org/html5/webvtt/
   */
  
  #include "avformat.h"
  #include "internal.h"
  
  static void webvtt_write_time(AVIOContext *pb, int64_t millisec)
  {
      int64_t sec, min, hour;
      sec = millisec / 1000;
      millisec -= 1000 * sec;
      min = sec / 60;
      sec -= 60 * min;
      hour = min / 60;
      min -= 60 * hour;
  
      if (hour > 0)
          avio_printf(pb, "%02"PRId64":", hour);
  
      avio_printf(pb, "%02"PRId64":%02"PRId64".%03"PRId64"", min, sec, millisec);
  }
  
  static int webvtt_write_header(AVFormatContext *ctx)
  {
      AVStream     *s = ctx->streams[0];
      AVCodecParameters *par = ctx->streams[0]->codecpar;
      AVIOContext *pb = ctx->pb;
  
      if (ctx->nb_streams != 1 || par->codec_id != AV_CODEC_ID_WEBVTT) {
          av_log(ctx, AV_LOG_ERROR, "Exactly one WebVTT stream is needed.\n");
          return AVERROR(EINVAL);
      }
  
      avpriv_set_pts_info(s, 64, 1, 1000);
  
      avio_printf(pb, "WEBVTT\n");
      avio_flush(pb);
  
      return 0;
  }
  
  static int webvtt_write_packet(AVFormatContext *ctx, AVPacket *pkt)
  {
      AVIOContext  *pb = ctx->pb;
      int id_size, settings_size;
      uint8_t *id, *settings;
  
      avio_printf(pb, "\n");
  
      id = av_packet_get_side_data(pkt, AV_PKT_DATA_WEBVTT_IDENTIFIER,
                                   &id_size);
  
      if (id && id_size > 0)
          avio_printf(pb, "%.*s\n", id_size, id);
  
      webvtt_write_time(pb, pkt->pts);
      avio_printf(pb, " --> ");
      webvtt_write_time(pb, pkt->pts + pkt->duration);
  
      settings = av_packet_get_side_data(pkt, AV_PKT_DATA_WEBVTT_SETTINGS,
                                         &settings_size);
  
      if (settings && settings_size > 0)
          avio_printf(pb, " %.*s", settings_size, settings);
  
      avio_printf(pb, "\n");
  
      avio_write(pb, pkt->data, pkt->size);
      avio_printf(pb, "\n");
  
      return 0;
  }
  
  AVOutputFormat ff_webvtt_muxer = {
      .name              = "webvtt",
      .long_name         = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
      .extensions        = "vtt",
      .mime_type         = "text/vtt",
      .flags             = AVFMT_VARIABLE_FPS | AVFMT_TS_NONSTRICT,
      .subtitle_codec    = AV_CODEC_ID_WEBVTT,
      .write_header      = webvtt_write_header,
      .write_packet      = webvtt_write_packet,
  };