title: ffmpeg watermark first 30 second
body: <pre><code>ffmpeg -i v.3gp -acodec copy -vf "movie=w.png [logo]; [in][logo] overlay=10:main_h-overlay_h-10 [out]" nv.3gp
  </code></pre>
  
  <p>It work's fine, but i want watermark only first 30 seconds.
  Any ideas?</p>