Vlc Media Player Volume 400 Direct
Using --audio-filter=volume,volume (not allowed natively) would require forking VLC source.
Instead of dragging the slider to 400%, you can apply permanent gain to a file: vlc media player volume 400
What if you want to burn that 400% volume boost into the video file itself? For example, you have a quiet MP4 that you want to put on your phone, but your phone's video player doesn't have a 400% option. VLC will create a new video file that
VLC can convert the file with a permanent volume boost. vlc media player volume 400
The conversion guide:
VLC will create a new video file that is permanently 400% louder. When you play it on any device (iPhone, TV, car stereo), 100% volume on that device will now sound like 400% did in VLC. Warning: This file will clip if played on high-end systems.