Ubuntu has very convenient function to generate screencast. My favorite is gtk-recordMyDesktop. However, my mic isn’t very high quality and my screencast always ends up with annoying background noise.
Actually, this noise can be easily removed by denoising tools such as Audacity. One just needs to exact the audio track, denoise it with Audacity, and merge the audio back to the video. For this, one should install Audacity, oggz-tools, and oggvideotools. Simply run
sudo apt-get install oggvideotools oggz-tools audacity
to install the packages.
Now, to exact the audio track from the video, run
It should generate three files: an unknown ogv file, theora ogv file, and vorbis oga file. Now, open audacity and import the oga file, we will use audacity to remove the background noise.
In audacity, select a segment of audio that contains only background noise. Audacity will need it to learn the noise profile. After selecting the segment, go to Effect -> Noise Removal in the menu, and click Get Noise Profile.
Now select the entire audio, go to Effect -> Noise Removal again, but click OK instead.
Your audio track should now be denoised. We should now export the audio as Ogg Vorbis Files for the next step.
Let say the denoised audio is vorbis.ogg. We can now merge to the theora ogv file created earlier using
oggz-merge -o denoised-video.ogg theora.ogv vorbis.ogg