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Discriminating and filtering regularly spaced impulse noise in an audio stream

Started by JHD January 31, 2006
I'm digitally sampling and cleaning up some old vinyl albums.  The tough nut 
is obviously discriminating pops/clicks due to scratches on the record from 
transients in the music.  I'm using a package called Diamond Cut 6, which is 
powerful and flexible in terms of the number and type of filters it can 
produce, both fixed and adaptive.  It offers both time and frequency domain 
filters, which can adjust their threshold according to some local average of 
high frequency energy, etc. etc.  I'm pretty happy with it in general, 
although I'm still finding there's a tradeoff between leaving some clicks in 
the result, or signifiantly changing the spectral characteristics of the 
music.

It strikes me that knowing the period of revolution of the record gives a 
potentially powerful piece of information:  At 33.33 RPM, any impulse that 
repeats every 1.8 seconds would be highly likely to be due to a defect in 
the vynyl surface, and not part of the music.  My question to the algorithm 
gurus out there is, how would you take advantage of this information to do a 
better job of knowing when to filter aggressivly and when not?

Any thoughts?

J 


I would just use a median filter.


JHD wrote:
> I'm digitally sampling and cleaning up some old vinyl albums. The tough nut > is obviously discriminating pops/clicks due to scratches on the record from > transients in the music. I'm using a package called Diamond Cut 6, which is > powerful and flexible in terms of the number and type of filters it can > produce, both fixed and adaptive. It offers both time and frequency domain > filters, which can adjust their threshold according to some local average of > high frequency energy, etc. etc. I'm pretty happy with it in general, > although I'm still finding there's a tradeoff between leaving some clicks in > the result, or signifiantly changing the spectral characteristics of the > music. > > It strikes me that knowing the period of revolution of the record gives a > potentially powerful piece of information: At 33.33 RPM, any impulse that > repeats every 1.8 seconds would be highly likely to be due to a defect in > the vynyl surface, and not part of the music. My question to the algorithm > gurus out there is, how would you take advantage of this information to do a > better job of knowing when to filter aggressivly and when not? > > Any thoughts? > > J