I made a video of how to emphasize (add a circle over a face) things in a video with Avidemux. The same can be done for adding a blur with a different filter – Mplayer delogo.
However, blurring just one part of the video with the Mplayer delogo filter once failed on me. I wanted to add a blur just for five seconds over a face in a longer video. If I didn’t specify the frames (Partial button in step 5 of the previous tutorial) I got the blur over the whole length of the video. With Partial selected I ended up with a destroyed video.
Let say I want to add a blur from the frame 500 to the frame 600 on a video of 1000 frames.
1. Split the video in 3 parts
Use the reddish buttons A & B at the bottom of the video to select UNDESIRED parts of it and use Edit->Delete to cut bits of the video out. Save each part as it’s own file (no encoding needed so both video and audio remain on Copy) so we end up with 3 files: first from frame 0-499, second from frame 500-600 and third from frame 601-100.
2. Add a blur to the second video file
Use the procedure of the previous tutorial but select Mplayer delogo as a filter (and don’t forget to encode the video).
3. Concatenate the three videos.
Open the first one and select File->Append to add the other two in the right order
Here’s the video (sorry I forgot to turn the mic on but it’s short and self explanatory).