title: ffmpeg with m3u8: video and audio not synchronized
body: <p>I noticed while using <strong>ffmpeg</strong> to download m3u8 streaming playlist, I get sometimes faster video. 
  If the content of the url <strong>master.m3u8</strong> is the following:</p>
  
  <pre><code>#EXTM3U
  #EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=620941,RESOLUTION=640x352,CODECS="avc1.4d401f,mp4a.40.2"
  https://hello/world.m3u8
  </code></pre>
  
  <p>If I'm not mistaken, <strong>ffmpeg</strong> should be able to decode the <strong>EXT-X-STREAM-INF</strong> information and assign the default value while downloading.
  But when I run the following command:</p>
  
  <pre><code>ffmpeg -i "https://hello/darkness/my/old/friend/master.m3u8" -c copy "Some Video File.ts"
  </code></pre>
  
  <p>I get a video that is faster than the Audio.
  If I run this command without the <strong>-c copy</strong>:</p>
  
  <pre><code>ffmpeg -i "https://hello/darkness/my/old/friend/master.m3u8" "Some Video File.ts"
  </code></pre>
  
  <p>I get a video and audio synchronized. But the video quality is worse. </p>
  
  <p>What's the problem?</p>