text: /*
   * On2 VP8 parser for Ogg
   * Copyright (C) 2013 James Almer
   *
   * 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/intreadwrite.h"
  
  #include "avformat.h"
  #include "internal.h"
  #include "oggdec.h"
  
  #define VP8_HEADER_SIZE 26
  
  static int vp8_header(AVFormatContext *s, int idx)
  {
      struct ogg *ogg = s->priv_data;
      struct ogg_stream *os = ogg->streams + idx;
      uint8_t *p = os->buf + os->pstart;
      AVStream *st = s->streams[idx];
      AVRational framerate;
  
      if (os->psize < 7 || p[0] != 0x4f)
          return 0;
  
      switch (p[5]){
      case 0x01:
          if (os->psize < VP8_HEADER_SIZE) {
              av_log(s, AV_LOG_ERROR, "Invalid OggVP8 header packet");
              return AVERROR_INVALIDDATA;
          }
  
          if (p[6] != 1) {
              av_log(s, AV_LOG_WARNING,
                     "Unknown OggVP8 version %d.%d\n", p[6], p[7]);
              return AVERROR_INVALIDDATA;
          }
  
          st->codecpar->width         = AV_RB16(p +  8);
          st->codecpar->height        = AV_RB16(p + 10);
          st->sample_aspect_ratio.num = AV_RB24(p + 12);
          st->sample_aspect_ratio.den = AV_RB24(p + 15);
          framerate.num               = AV_RB32(p + 18);
          framerate.den               = AV_RB32(p + 22);
  
          avpriv_set_pts_info(st, 64, framerate.den, framerate.num);
          st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
          st->codecpar->codec_id   = AV_CODEC_ID_VP8;
          st->need_parsing      = AVSTREAM_PARSE_HEADERS;
          break;
      case 0x02:
          if (p[6] != 0x20)
              return AVERROR_INVALIDDATA;
          ff_vorbis_stream_comment(s, st, p + 7, os->psize - 7);
          break;
      default:
          av_log(s, AV_LOG_ERROR, "Unknown VP8 header type 0x%02X\n", p[5]);
          return AVERROR_INVALIDDATA;
      }
  
      return 1;
  }
  
  static uint64_t vp8_gptopts(AVFormatContext *s, int idx,
                              uint64_t granule, int64_t *dts)
  {
      struct ogg *ogg = s->priv_data;
      struct ogg_stream *os = ogg->streams + idx;
  
      int invcnt    = !((granule >> 30) & 3);
      // If page granule is that of an invisible vp8 frame, its pts will be
      // that of the end of the next visible frame. We subtract 1 for those
      // to prevent messing up pts calculations.
      uint64_t pts  = (granule >> 32) - invcnt;
      uint32_t dist = (granule >>  3) & 0x07ffffff;
  
      if (!dist)
          os->pflags |= AV_PKT_FLAG_KEY;
  
      if (dts)
          *dts = pts;
  
      return pts;
  }
  
  static int vp8_packet(AVFormatContext *s, int idx)
  {
      struct ogg *ogg = s->priv_data;
      struct ogg_stream *os = ogg->streams + idx;
      uint8_t *p = os->buf + os->pstart;
  
      if ((!os->lastpts || os->lastpts == AV_NOPTS_VALUE) &&
          !(os->flags & OGG_FLAG_EOS)) {
          int seg;
          int duration;
          uint8_t *last_pkt = p;
          uint8_t *next_pkt;
  
          seg = os->segp;
          duration = (last_pkt[0] >> 4) & 1;
          next_pkt = last_pkt += os->psize;
          for (; seg < os->nsegs; seg++) {
              if (os->segments[seg] < 255) {
                  duration += (last_pkt[0] >> 4) & 1;
                  last_pkt  = next_pkt + os->segments[seg];
              }
              next_pkt += os->segments[seg];
          }
          os->lastpts =
          os->lastdts = vp8_gptopts(s, idx, os->granule, NULL) - duration;
          if(s->streams[idx]->start_time == AV_NOPTS_VALUE) {
              s->streams[idx]->start_time = os->lastpts;
              if (s->streams[idx]->duration && s->streams[idx]->duration != AV_NOPTS_VALUE)
                  s->streams[idx]->duration -= s->streams[idx]->start_time;
          }
      }
  
      if (os->psize > 0)
          os->pduration = (p[0] >> 4) & 1;
  
      return 0;
  }
  
  const struct ogg_codec ff_vp8_codec = {
      .magic     = "OVP80",
      .magicsize = 5,
      .header    = vp8_header,
      .packet    = vp8_packet,
      .gptopts   = vp8_gptopts,
      .nb_header = 1,
  };
  