Removing Hiss from Video

Software such as Virtualdub, VirtualdubMod and Avidemux can be used to extract the audio first, then the audio can be enhanced separately before being muxed again.

Other Hiss Removal Tools

A VST plugin for Audacity, JS Noise Filtre is capable of producing decent results for all sorts of background noise.

Plain Text

Another feature is NOISE REMOVAL.
This tackles  minor  hiss or background noise.
First select an area of pure noise.
Use that for getting the noise profile.
The noise has now been removed.
Apply noise removal to all affected areas.
And check the results.
Listen out for distortion.
If there is a lot of distortion, then undo the changes.
...And keep the original.