Some audio output from files or streams is too low. It is obvious that hardware is able to play the same sounds but louder but because of the data it just plays it at some low level even at 100% volume. Vlc can generally increase the volume of a file up to 200%. Is there a way to do the same thing VLC does system-wide and if possible for an arbitrary v percentage value.
If there is no application that does this, where should i look into for libs to do it myself or what code should I modify (e.g. code in the alsamixer).
PulseAudio will allow you to overdrive an individual stream or device to 400-500% via the manager (paman). Simply examine the properties of the stream or device in question, and adjust the volume slider appropriately.
A simple volume control tool (mixer) for the PulseAudio sound server.
In contrast to classic mixer tools this one allows you to
control both the volume of hardware devices and of each playback stream separately.
It also allows you to redirect a playback stream
to another output device without interrupting playback.
In Ubuntu [at least 14.04] you can go to the volume "system tray slider" and select sound settings. Then select the "allow louder than 100%" checkbox, now your volume control goes up to like 400% or something. This can seemingly be used in conjunction with paman, FWIW.