cleaning vinyl audio? Reply #25 – 2009-01-06 21:13:49 Reissues of LP on Cd are often quite different.I will copy here a post I made some years ago discussing a technique I worked out with CoolEdit/Audition. It is quite labor intensive but can be faster than straightforward manual declicking. I don't use it often, it usually isn't necessary to get very good results, but it is a method that lets you know exactly what you are doing to the file.EXTREME DECLICKINGI held off writing this up for quite a long time because I suspect it will have very limited appeal. The recent post about the destructed drum attacks goaded me into action. Most people will decide that the automatic declicking they now use is good enough. Perhaps they won't even want to know how much good material goes ‘out with the bath water,' but if your results are not satisfactory, there is a better way. I myself only do this for extreme cases.Although all declicking aalso removes good material, there are two ways around most of that problem. Almost flawless results are possible if the source LP is in reasonably good condition. It is still as Graeme said, "that you can't get 'something for nothing' ", but for more time and effort you can get better results.The straightforward method is to do only manual declicking. Manual declicking often does a better job on any individual click than is possible with automatic declicking. This difference is frequently fairly subtle but it is real and often enough the difference isn't subtle at all. More importantly, however, one can stay away from almost all legitimate musical transients, resulting in no dulling or loss of impact.The second method is a bit more complex but can demand less intensive effort than strict manual declicking. It is adaptable from the extreme of just preventing the worst of automatic over processing to the extreme of striving for click removal perfection. It is a variation of a technique introduced by Alofoz, but adapted to allow virtually absolute control. If you are blessed with a recording in good enough condition, simple manual declicking will take less time, but for a bad to terrible disk, this second approach is easier and offers better results. To use this approach, one needs to check ‘limit playback to: mono' in the device settings.Proceedings are much easier if one involves only declicking in this adventure. This means that between the baseline beginning file and the declicked working file one does no noise reduction, no equalization, no normalization, no whatever. Any and all other processing can be done either before or after the declicking, just not between the baseline file and the declicked working file.If using the Sonic Foundry declicking plugin, you must uncheck ‘remove subsonic rumble,' or probably better, first processing the file with ‘remove subsonic rumble' checked but with the three sliders all the way to the left. Use the result as the baseline file.The declicked working file is what comes out of automatic declicking. This can be one step of declicking or as many steps as one wishes, especially including the Younglove decrackling process. The ideal is a perfectly declicked file, but as the starting assumption for this journey is that perfection cannot be achieved via automatic declicking, we strive for a file that is so adequately declicked it needs little or no additional declicking, while not being too badly destroyed from over processing. From here, we can eliminate the destruction and tidy up the proper declicking. Over declicked is better than under declicked, but anything more than necessary just increases the time and effort of correction.You next need a file of inverted clicks. If your declicking of choice is a one step process (e.g. no Younglove decrackling run after major declicking), and if you do it with some tool, like ClickFix or Sonic Foundry, that has a "keep clicks only" option, you can use that option to end up with a file containing just the removed clicks, no music. Sonic Foundry automatically inverts the retained clicks. ClickFix's output must be inverted before proceeding. If using CoolEdit/Audition, or some other declicker that only gives you declicked music, or doing multi pass declicking, do a Mix Paste/Invert of the baseline file into the fully declicked audio file to obtain a file of inverted clicks.This inverted click file contains everything removed from the baseline, the good, the bad, and the terrible trumpet distortions. Eventually it will contain only the good and we will mix it into the baseline file to achieve whatever degree of declicking nirvana we were willing to strive towards. First there is some deconstruction.From the two files, baseline and inverted clicks, we need to created two other files, but to accomplish that we first need to create four intermediate files. There are some manipulations that require less disk space, but I will describe only the most straightforward. If disk space is an issue, everything between the baseline file and the inverted click file can now be deleted. Likewise, the next four intermediate files can be deleted immediately after use, but sometimes it can be very useful to keep most intermediated results around for reference until everything is finished.Open the baseline file in single waveform view (i.e. not multi-track). Select all of one channel. Save that selection as a new file. Do the same for the other channel. You now have two intermediate files, mono right channel and mono left channel. Be certain to use names that will not leave you confused as to which is what after a few more steps.Do the same thing with the inverted clicks. Now you have the four intermediate (mono) files I mentioned, the delete able ones. From these four you will build two 2 channel working files, one containing the right channel and its inverted clicks, the other containing the left channel and its inverted clicks. These also must get names that leave nothing to chance. In these, I like to have the audio as the right channel, so it appears on the bottom of the edit screen, and the inverted clicks as the left channel so they appear on the top of the screen, for both the left and right channel files. Your arraignment is your choice.The easiest way to build these two files is via multi-track. Insert the mono inverted clicks into track 1 and the mono baseline audio into track 2. Pan track 1 100% left (-100) and track 2 100% right (+100). Select both. Mix down into a two channel file. You can also accomplish this in waveform view with copying and pasting or the Mix Paste function, but multi-track seems easier to me.Now when you open one of the files (in edit mode) you will have the unprocessed audio on one channel and the inverted clicks on the other. When you play the file, due to the ‘limit playback to mono' setup, you will here the declicked results. If you select only one channel to play, you will hear either the un-declicked baseline or the inverted clicks; either will be center stage. This would probably be very unfunctional when trying to create a masterpiece from a raw multi-track recording, but it works quite well to clean up an LP.I developed this so that I could work in Spectral View. Alofoz's technique, which uses multi-track, is undoubtedly well suited to getting good sounding results, but I need, and you need, Spectral View (and destructive editing) if, perchance, we are attempting declicking distinction. In Spectral View, with a little practice, it is generally easy to see the good material that any auto declicking removes. Since you can see it, you don't have to also spend the time listening to it, you can just fix it straight away. In Waveform view, on the other hand, many clicks have a clear enough appearance, but the good material that is inadvertently removed through automatic declicking is frequently much less distinct.From here there are many degrees of involvement. It is possible to review every millisecond, every removed smidgen, to assure that every sample is as good as the original recording into your computer will permit. It is also possible, with enough resolution and fortitude, to ignore everything except the worse problems areas (e.g. the drum strikes) and trust to the auto declicking for all else. To get the best results, one must work at a fairly high level of horizontal (time base) zoom.If you are new to Spectral View, it may take a little practice before everything becomes obvious, but the difference between musical transients and clicks is almost always unmistakable, especially since you have available the immediate comparison of the baseline recording and the removed material. Those drum strikes, and other transients that automatic processing incorrectly declicked, can be salvaged simply by selecting the offensive material on the inverted click channel and pressing the delete key. Now your drum strike, or trump blast, is preserved in pristine glory.There are a few things to note here. For optimum manual declicking, the click must be selected with some care. For this un-declicking, selection is faster and easier because you can select anything and everything that isn't a valid (inverted) click at one time, in one swoop. Select any number of events on the inverted click channel and any amount of blank space between them. Often, a double mouse click to select everything currently on screen is appropriate; delete it all with one keystroke.The only time it gets difficult or especially tedious is when good material (on the inverted click channel) is practically on top of a genuine click. In this case you may need to zoom in especially close to allow precision selecting. Sometimes it will be easier and faster to delete everything in that vicinity from the inverted click channel and do a manual declick of the offensive impulse noise on the baseline audio channel.As I said, much of this can be done visually; you can learn to identify good material on sight. However, as an aid, and sometimes as a necessity, when you play both channels together, you hear the mixed results, so you can identify the dulled impact and the over processed distortion audibly. You can also learn the more subtle degradation than any automatic declicking produces. If you select only the audio channel, you get the unprocessed recording and thus hear what you will be missing if the auto clicking result is allowed to stand.For some of the other possibilities of this technique, you do need to listen -- to both channels at once. Larger clicks too often don't get properly removed with any automatic declicking that I know about. After auto declicking, good material immediately adjacent to the click is ‘disturbed' and something from the click is left over, often a low frequency thump that is as unpleasant as the original click but more difficult to precisely locate (but here you can see exactly what and where because the original click is still right there, on the audio channel).Often it is easier to start from scratch to manually declick these than it is to repair the auto declicking damage. Simply swipe across the click channel to select everything related to the bad fix, delete it, and take your best shot at manual declicking. These large clicks often require multi-step manual declicking for best results.Removal of somewhat smaller clicks usually don't cause new damage, but the clicks themselves are partially left behind. This is usually only obvious when you listen to the results, not by looking at the Spectral image. Maybe this residue isn't a problem, depending upon the context, but is still isn't perfection. These partial corrections, when you care about them, like the gross ones of the preceding paragraph, are best fixed by simply deleting from the inverted click channel and manually declicking on the audio channel. If you simply manually declick, but don't delete the inverted click, your final results will still have the click -- inverted, but just as unpleasant.Because you are selecting only the inverted clicks channel, removing via the delete key is the proper thing to do. This has a danger. If you inadvertently select both channels, disaster will result. You are working on the file of either the right or left channel of your recording at any one time. Eventually you need to get the right and left channels back together. If you delete with both inverted click channel and music channel selected, the file becomes shorter by the amount deleted. The right and left music channels, temporarily in separate files, will no longer be in sync. You will be very unhappy.In the lower right hand corner of the screen is a box with the total file time. The last three digits, the number of milliseconds, can be used as a quick hash count check. If that number ever changes, you did the wrong thing. Pray there are enough undoes available to recover.I don't know about other version of the software (I use CE2K) or other hardware, but after I've removed a jillion or so clicks manually, or deleted enough incorrect declicks in this scenario, my screen gets hinky. This is a sign of coming end times. I delay that eventuality by occasionally purging undoes and clicking on save -- check the total file time before saving. If the impending crash stigmata still eventually appears, I note where I am current working (by the time display), save, close the program. Everything is fine when I re-open, but the pk file will generally be rebuilt in the process of opening.I have never deleted portions of a recording (right and left music together) to correct a problem, but I understand from various comments that this is not a particularly uncommon technique. To use it here you will have to select the music section to be deleted and install Que marks. Then when the right and left channels are rejoined, use the que marks to delete from both channels at once.Once each file, right and left -- inverted click channel plus music channel together -- are satisfactory, you start consolidating. Once again there are several possible approaches: mix paste; copy/paste; channel mixer; pull apart, insert into multi-track, and mix down; convert sample type. Convert sample type is easy. Select Mono in the channels box and make sure resolution and sample rate are not being changed. Once converted into mono, Save As a new mono file with a good name. That mono file is the mix of inverted clicks and audio -- the perfectly, or at least adequately to your standards, declicked audio.Now you have two more files, the perfectly declicked right channel and the perfectly declicked left channel. Put them back together. The multi-track solution seems easiest to me, used exactly as it was to created the inverted click-music files. Take care to insert left into track one and right into track two. Pan track 1 hard left and track 2 hard right, select both tracks, mix down, save the result.