How to animate ffmpeg's boxblur
<p>I am running the following ffmpeg command which converts a single image to a 10 second slow-zoom into the center of the photo.</p>

<p>As you can see, I currently have the <code>boxblur</code>looking how I would like it, but it is applied to the entire 10 second clip. I'd like to blur the first 3 seconds, and then animate the radius of the blur from it's current value of <code>boxblur=10:9</code> to <code>boxblur=0:0</code> from 3.0 - 4.0 seconds (24 frames at 24p).</p>

<pre><code>ffmpeg -loop 1 -framerate 24 -i image.jpg -vf "boxblur=10:9,zoompan=z='min(zoom+0.0005,1.12)':x='iw/2-(iw/zoom/2)':y='ih/2-(ih/zoom/2)':d=240:s=hd1080:fps=24" -c:v libx264 -pix_fmt yuv420p -t 10 -s hd1080 -crf 20  video.mp4
</code></pre>

<p>Any help on how to achieve this?</p>