How do I remove hiss?

I have an avi movie that has a hiss on the sound, what is the easiest way to remove it?

That´s a big job
You will have to demux the movie, then clean the sound in an audio editor, then put it back together.

What´s the movie and source?

TMPGEnc Xpress has some basic audio filters, so the file can be processed as one, but like [B]deanimator[/B] say, it depend on file format.

It is an avi movie I downloaded

As deanimator said, you can remove the audio stream, try to run it through a filter, then recombine the audio and video. You can use Virtualdub to extract the audio to a .wav file. Finding a good audio program that can do the filtering for free is the problem. Audacity is free, but from what I’ve read, this type of filtering is not one of its strong points. Do a Google search on “remove hiss with Audacity”.

You could also try the free trial of Goldwave. It is supposed to be fully functional for the length of the trial.

I´ve had mixed success with removing tape-hiss using Audacity.

For example: I´m doing 3 audio tapes at the moment…I tried several times with different noise reduction %s of effect…but the result sounded thin and developed a bit of an echo. I gave up and opened the tracks in Nero WaveEditor…same technique: took a short noise print and applied it at 45% over the entire track…almost perfect noise reduction and no noticeable deterioration in overall tonal values of the audio.