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White Noise Suppression causes clicks

 
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Usabell



Joined: 16 Dec 2010
Posts: 12

PostPosted: Wed Jan 26, 2011 6:41 am    Post subject: White Noise Suppression causes clicks Reply with quote

Since my other thread got hijacked multiple times and it seems that my answer there was somehow too hidden/lost or something, and no reply to the actual topic was made for a month now, I am going to start a new thread that covers the only single problem left. Thanks a lot for fixing the clipping problem with the White Noise suppression in the other thread! It definitely fixes the clipping issue the old version had, but still keeps the problems with the first few samples of a sound.

You can download these sound files to see the effects here:

http://audio.daniellippert.ch/HAUEP_D4_D4_E4_41_45.wav

http://audio.daniellippert.ch/HAUEP_F2_F2_G2_106_110.wav

On both of these sounds, after processing with -45 dB of White Noise Suppression applied, the waveform does not start at zero (vertical middle) on the very first sample (waveform starts without a zero crossing), like it did with the unprocessed sound files. You need to zoom in at the beginning to see this, and it can be clearly heard as a "tick" or "click" at the beginning portion of the sound. It seems that the noise suppression algorithm generates a click out of nowhere, if you watch the difference between unprocessed and processed sound. You can see what I am talking about here:

http://audio.daniellippert.ch/showdiff.png

The pink curve in this picture shows the sound wave after the processing, the dark blue curve is the curve of the original WAV file.

I really hope this can be fixed because I already started to work on this project more than a month ago and I need denoised non-clicking versions of these two and over 1000 other sounds.

Thanks in advance for looking into this!
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Martin Hairer
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Joined: 08 Nov 2006
Posts: 1612

PostPosted: Wed Jan 26, 2011 8:26 pm    Post subject: White Noise Suppression causes clicks Reply with quote

I am afraid that this kind of artefact is pretty much unavoidable.
You can easily create a batch processor that adds a "Fade In"
on the first couple of milliseconds, which would fix the problem.
Regards,

Martin

HairerSoft
http://www.hairersoft.com/



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Usabell



Joined: 16 Dec 2010
Posts: 12

PostPosted: Thu Jan 27, 2011 1:46 am    Post subject: Reply with quote

Oh, I am really sorry to hear that it can't be avoided. Funnily, Amadeus' White Noise Suppressor works much better than any other noise reduction algorithms I tried on this sound material, but the generated click changes the attack portion of the sound too much to be usable as a final product. I already tried the fade in trick (which was one of my first attempts to quickly fix this behavior, to be honest) but it somehow dampened the attack too much, even at very short fade-in times, so none of that worked. I am no DSP programming expert, but I wonder how a noise suppression algorithm creates such a harsh transient out of an almost silent portion of sound. Well, anyway, thanks for looking into this, I have to try out different solutions now and see which one has the least loss for my (important) transient material. I think the support for Amadeus is really great and I'll definitely continue to recommend it to all the people I know. Keep it up! Smile

EDIT: Looking one last time at the combined screenshots I posted I was just wondering if it wouldn't be an easy and also effective solution to, like, crossfade the unprocessed first, say, 30-40 samples with the processed sample material. It would definitely cancel out any unwanted clicking artifacts at the beginning of the sound, and I don't think any noise during the first 40 samples would be noticable to the human ear, so no loss here, either. The crossfade would have to be rather quick during the last 10 or so samples of the first 40 samples, and all samples before that could be taken over 1:1 from the unprocessed original. Well, just an idea, you decide Smile
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CDJonah_alt



Joined: 15 Mar 2007
Posts: 378

PostPosted: Thu Jan 27, 2011 2:41 am    Post subject: White Noise Suppression causes clicks Reply with quote

Can you add something to the beginning of the file so that the click is
outside the region where you need data?

On 1/26/11 7:46 PM, Usabell wrote:
Quote:
Oh, I am really sorry to hear that it can't be avoided. Funnily, Amadeus' White Noise Suppressor works much better than any other noise reduction algorithms I tried on this sound material, but the generated click changes the attack portion of the sound too much to be usable as a final product. I already tried the fade in trick (which was one of my first attempts to quickly fix this behavior, to be honest) but it somehow dampened the attack too much, even at very short fade-in times, so none of that worked. I am no DSP programming expert, but I wonder how a noise suppression algorithm creates such a harsh transient out of an almost silent portion of sound. Well, anyway, thanks for looking into this, I have to try out different solutions now and see which one has the least loss for my (important) transient material. I think the support for Amadeus is really great and I'll definitely continue to recommend it to all the people I know. Keep it up! Smile




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Usabell



Joined: 16 Dec 2010
Posts: 12

PostPosted: Thu Jan 27, 2011 2:53 am    Post subject: Reply with quote

An interesting idea! I just added 0.1 seconds of silence before the sound, and it resulted in a very different and at the same time interesting waveform. Instead of a sharp clicky attack it became a jittery, slowly rolling in shape before the actual sound starts. Somehow the noise suppression seems to look forward into future samples and generates some things depending on what it sees coming in the future. Maybe I can make a batch function that adds silence to the beginning, then processes the sound, then cuts the silence and fades in the very first bit, but the aforementioned fading method in my edit would be even better, even though I now doubt it will work because of the much longer artifacts it creates with the added silence at the beginning. The amount of samples that are altered from the "normal" waveform seems to depend on the actual waveform and the amount of silence in front of the sound, so it will be hard to predict the exact number of samples where the crossfading needs to take place. Sad
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CDJonah_alt



Joined: 15 Mar 2007
Posts: 378

PostPosted: Thu Jan 27, 2011 3:36 am    Post subject: White Noise Suppression causes clicks Reply with quote

As far as I know, unless one does some very clever things that basically
turns on the filtering as you go through, you always get what are called
endpoint problems. As you note, it looks ahead, because of course, it
can't look behind at the beginning. I would try adding something like a
second at either end and then see if you can work out a batch process to
delete a second at either end.

Chuck

On 1/26/11 8:53 PM, Usabell wrote:
Quote:
An interesting idea! I just added 0.1 seconds of silence before the sound, and it resulted in a very different and at the same time interesting waveform. Instead of a sharp clicky attack it became a jittery, slowly rolling in shape before the actual sound starts. Somehow the noise suppression seems to look forward into future samples and generates some things depending on what it sees coming in the future. Maybe I can make a batch function that adds silence to the beginning, then processes the sound, then cuts the silence and fades in the very first bit, but the aforementioned fading method in my edit would be even better, even though I now doubt it will work because of the much longer artifacts it creates with the added silence at the beginning. The amount of samples that are altered from the "normal" waveform seems to depend on the actual waveform and the amount of silence in front of the sound, so it will be hard to predict the exact number of samples where the crossfadi
ng
Quote:
needs to take place. Sad




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