Often, when I have a large number of media files playing in VLC, the most annoying problem for me is that for each file, I have to manually adjust the volume for them (so that they are not to loud). Moreover, for those music video files, I have to deal with the issue about screen resolution and ratio. My screen’s ratio is 16:10 but most of my videos are in 4:3 or 16:9 ratio.
The word normalize here means that to force all the media files to behave in a same way so that I can enjoy them without worrying to adjust for each file.
Open VLC Preferences panel, head to the Audio tab, select Volume Normalizer and adjust the number in the beside textbox (from 0.5-10). The lower the number is, the lower the sound would be and the higher the volume you need to adjust. Try open some media files and then figure out which number is best suitable for you.
Auto Fit Videos to Screen
Open VLC Preferences again, this time select All to show advanced configuration panel.
Head to Video section, concentrate on 2 textbox Video Cropping and Source Aspect Ratio. Depending on your favor that you want VLC to crop or stretch your video files, input your screen ratio to the appropriate textbox.