I seldom join forums of any kind. However, I have learned a lot by browsing through the archives of the Audio Masters forum and I wanted to share a few tips based on my experience with declick and denoise.
I am still working with Cool Edit Pro 2 which fills most of my needs as I am mostly interested in restoring or improving the audio quality of older or poorly mastered recordings. However, like others, I found cool edit's abilities and declicking a bit wanting. Cool Edit's own declicker is very slow and adds a lot of artifacts. (I love the remove single click function, however.) I tried the Younglove decrackling technique, but with mixed results. First, it took a long while to declick a track and second, sometimes artifacts were present in the final result. I had other declick plugins and found them pretty much useless for removing clicks w/o artifacts. However, after playing around with the limited tools I had I found a way to use them to achieve pretty good, and in some cases, excellent results. The only thing I used was cool edit itself and a declick plugin that let me output the noise itself. In this case, it was a very old Steinberg declicker; I think it was the first Steinberg ever. Having used it in the conventional way, I thought it was totally useless for two reasons: First it added all sorts of unpleasant artifacts, and second it only worked on the entire file; you could not work on only a portion of it w/o losing some data and putting your selection out of sync with the rest of the audio.
However, using Younglove's principle of divide and conquer, I found a way to get very good results with this otherwise unsatisfactory plugin. I imagine that a better plugin would give you equally good or better results.
The basic idea was based on my assumption that clicks don't have any particular frequency, but they do fall into a more limited range of amplitudes. So my basic declicking approach comes down to this:
1. Isolate the noise by selecting only data of a lower amplitude
2. Amplify this noise
3. Declick the amplified noise keeping only the clicks as the output
4. Restore the clicked output to its original volume
5. Invert the noise
6. Mix/paste the inverted declicked noise with the original file.
Although the last 2 steps could be eliminated, I like to keep the noise inverted so that I can keep track of what I am subtracting and maintain the original file uninverted. For me, it keeps things simpler.
Often I will repeat this process more than once using lower amplitude ranges to capture smaller clicks.
The way I initially isolate the noise is by keeping the output of the dehiss function, something I otherwise never had any use for.
After searching for a place to park some examples on the web I found a site and put two mp3's there. This is an out of copyright recording of Enrico Caruso. The first link has the original data and the second declicked. Obviously, with a recording this old and noisey you are not going to get total quiet, but there is a substantial reduction in the background clicks, without a loss of audio quality. I have found that this approach can work very well on sublter noise as found on old LP's. However, if the source is from 78's that sound as if they were play for decades using cactus needles, declicking is not really going to fix it. It will remove some of the clicking but as the noise is constant and severe it will also introduce other types of distortions.
Anyway, judge for yourself. If you have questions, post them. I will check in once a week or so for the next month or so. (posted 4/20/08)
http://www.mediafire.com/?byadbz2gjlw
o holy night Caruso no declick
http://www.mediafire.com/?dwyg1bz1fwg
cantique de noel Caruso with declick
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