title: Ffmpeg burnt in subtitles out of sync when converting to hls
body: <p>I have a file that has subtitles burn into it and they are perfectly in sync.</p>
  
  <p>Here is the file. <a href="https://983yqbz442.s3.amazonaws.com/little-mermaid-captions.mp4" rel="nofollow noreferrer">https://983yqbz442.s3.amazonaws.com/little-mermaid-captions.mp4</a></p>
  
  <p>I run this command to convert to hls and it creates the .ts files and the .vtt files.</p>
  
  <pre><code>ffmpeg -i little-mermaid-captions.mp4 -profile:v baseline -level 3.0 -s 640x360 -start_number 0 -hls_time 10 -hls_list_size 0 -f hls index.m3u8
  </code></pre>
  
  <p>I also then create a master.m3u8 file in the same folder with the following.</p>
  
  <pre><code>#EXTM3U
  #EXT-X-VERSION:3
  #EXT-X-INDEPENDENT-SEGMENTS
  #EXT-X-STREAM-INF:BANDWIDTH=800000,RESOLUTION=640x360,SUBTITLES="subtitles"
  index.m3u8
  #EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="subtitles",NAME="English",DEFAULT=YES,AUTOSELECT=YES,FORCED=NO,LANGUAGE="ENG",URI="index_vtt.m3u8"
  </code></pre>
  
  <p>Now if I play the master.m3u8 file the subtitles are now out of sync and are about 1 sec to quick. I understand this is probably a setting I am missing through FFmpeg but really stuck on this and would appreciate any insight.</p>
  
  <p>Thanks</p>
  
  <p>More info.</p>
  
  <p>Here is a link to the direct .m3u8 this can be opened in Safari.</p>
  
  <p><a href="https://983yqbz442.s3.amazonaws.com/hlstests/master.m3u8" rel="nofollow noreferrer">https://983yqbz442.s3.amazonaws.com/hlstests/master.m3u8</a></p>
  
  <p>The generated vtt file is here.</p>
  
  <p><a href="https://983yqbz442.s3.amazonaws.com/hlstests/subs-0.vtt" rel="nofollow noreferrer">https://983yqbz442.s3.amazonaws.com/hlstests/subs-0.vtt</a></p>
  
  <p>If you look at the start of the .vtt file you will see this.</p>
  
  <pre><code>WEBVTT
  
  00:06.840 --&gt; 00:10.320
  once long ago in the deep blue below
  </code></pre>
  
  <p>It should start at 00:06.840 but when playing the .m3u8 file in Safari you should see it starts at around 5 seconds not 6 about a second too early.</p>