title: How to render a watermark with transparency into a video
body: <p>I'm trying to render a watermark into a video. The moment the image file (.png) for the watermark contains transparency the image isn't rendered into the video anymore. If I convert that image to .jpg and back to .png it works well. If I create a new png that don't have transparency it works too. But when I add e.g. layer opacity to that image it isn't rendered anymore.</p>
  
  <p>I use avconv 0.8.6-4:0.8.6-0ubuntu0.12.04.1 with the following command</p>
  
  <pre><code>avconv -y -i video.mp4 -f 'movie=watermark.png [watermark]; [in][watermark] overlay=10:10 [out]' -c:v libx264 -t 255 -strict experimental out.mp4
  </code></pre>
  
  <p>If I use .gif for the watermark I get the image, but it's all opaque.</p>
  
  <p>Any clue?</p>