Ever downloaded a video from the internet that is barely audible? Fixing the audio volume is a simple matter of demuxing the video file into its constituting video and audio channels, adding a constant gain to the audio channel and then packing both together into a video container. This tutorial will show you how to do that. Years ago, I wrote a similar tutorial showing readers how to increase the volume of the audio channel of a video file using a software called VirtualDub. The method described worked only with AVI files. The new method that I’m going to describe in this tutorial works with common video formats such as MP4, MKV and AVI.