title: ffmpeg - reduce background audio noise when recording desktop screen with gdigrab
body: <p>I have an application that records desktop screen using FFmpeg. Here is the command I use</p>
  <pre><code>ffmpeg.exe -threads 4 -rtbufsize 2048m -f dshow -i audio=&quot;Microphone (Realtek Audio)&quot;  -f gdigrab -offset_x 1 -offset_y 1 -video_size 768x432 -probesize 4096M -i desktop -pix_fmt yuv420p -c:v libx264 -crf 28 -preset ultrafast -tune zerolatency -movflags +faststart -r 15 recording.mp4
  </code></pre>
  <p>It works fine. But I want to reduce the background noise from the audio. I have found some native filters for this</p>
  <ul>
  <li><a href="http://ffmpeg.org/ffmpeg-filters.html#afftdn" rel="nofollow noreferrer">afftdn</a></li>
  <li><a href="http://ffmpeg.org/ffmpeg-filters.html#anlmdn" rel="nofollow noreferrer">anlmdn</a></li>
  <li><a href="http://ffmpeg.org/ffmpeg-filters.html#arnndn" rel="nofollow noreferrer">arnndn</a></li>
  </ul>
  <p>But not sure how to use them while recording screen. Can you please help?</p>