Denoising audio in avisynth

[Malcolm]

Hi!
Recently, I had to denoise the audio-part of a tv-captured film. This task was really tedious, because the film was 2h 44m long. So i ended up swapping & processing nearly 2 gig of uncompressed WAV, before encoding it to MP2. A denoising-filter in avisynth would have been very helpful!
O.k. it might be, that avisynth is more focussed on video-processing. And this sort of audio-denoising-filter is too complicated to develop - or no one is interested in...
So, what about support for existing audio-filters from other applications? Cool Edit (a Shareware-Audio App) has a Filter-SDK on it's website. www.syntrillium.com (http://www.syntrillium.com/download/)
Or a Wrapper-Filter for avisyth could be made, that itself calls a Cool Edit-Filter. There could be 2 modes for the Wrapper-Filter; first mode to bring up the GUI-Dialog of the Cool Edit-Filter, feeding it with the audio from the avisynth-script, this to make settings and test the filter; the settings could then be written to a file. Second mode for processing the audio using the previous made settings.

What are your thoughts about that?

bye, Malcolm

[hakko504]

Don't know what kind of noise you have, but if you think a simple lowpass filtering will help, then that is already implemented in v2.05 of avisynth. Please refer to this page (sh0dan) (http://cultact-server.novi.dk/kpo/avisynth/avs_cvs.html) for recent changes and new cvs builds.

[Malcolm]

Hi hakko504,

there's a Cool Edit Filter with which you can make a Profile of your noise and the remove exactly _this_ kind of noise from your clip. You make this by selecting some seconds of silence in your clip - a part where only the noise is audible - and then let the filter analyse this part. Then you can change settings like strength, precision, masking, bla bla an apply the filter with your noise-profile to the whole clip.

There are screenshots and soundclips on the syntrillium-homepage (makers of Cool Edit) which illustrates this (and other) denoising-filters: Here's the link (http://www.syntrillium.com/cep/effects.html#nos)

I think lowpass filtering can't compare to that. Try it; there's a tryout-version of Cool Edit.
Btw. other Audio Apps have this sort of denoising-filters too.

bye, Malcolm

[sh0dan]

This feature is not very easy to do, since it involves high-precision FFT filtering, and that's not easily done.

For all you who wants to code, but don't know what it does, it's something like this:

CoolEdit generates a frequency response pattern from the "clean noise" is recieves. When this is done, it uses this frequency pattern to create a filter, that removes only the frequencies found in the noise, thus (in principle) leaving all non-noise untouched.

[jarthel]

there are good audio editing tools out there than using avisynth filters.

Jayel

[AviUser]

Use Sox Audio Effect Filter (http://forum.doom9.org/showthread.php?t=104792).
I have not tested it, but it look good.

[pandy]

ffdshow has "blind" noise removal filter so always ffdshow can be used inside Avisynth.

[hydra3333]

Any script examples of using it ?

[pandy]

ffdshowAudio ("name of profile in ffdshow") or
ffdshowAudio ("name of profile in ffdshow", options "name of parameter and value for parameter") - name of the parameter and value need to be discovered form ffdshow saved profile - just save exactly same profiles but with different values.

small explanation is in avisynth documentation - audio processing in ffdshow can introduce some delays in audio - need to be corrected by DelayAudio()