Use it to add an image to the write stream to see a recording banner on video echoed back to you during recording.
ARGS: <file> [<position>] [<opacity 0-255>]

POSITIONS:
left-top
left-mid
left-bot
center-top
center-mid
center-bot
right-top
right-mid
right-bot

<extension name="example">
  <condition field="destination_number" expression="^overlay$">
    <action application="answer"/>
    <action application="video_write_overlay" data="/path/to/img.png"/>
    <action application="record" data="/data/file.mp4"/>
    <action application="stop_video_write_overlay"/>
   </condition>
</extension>