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Forum List => General Discussion => Topic started by: camroncamera on February 24, 2013, 12:21:59 pm

Title: Combining Multi-Pass Waveforms
Post by: camroncamera on February 24, 2013, 12:21:59 pm
Greetings, this is my first post! I found my way here by way of Scot Hacker's Foobar Blog post The Compleat Guide to Digitizing Your LP Collection ( where Scot heartily recommends Vinyl Studio for recording vinyl to digital audio. As I am planning to embark on a digitizing project of my modest vinyl collection in the near future, I had posted a comment on his page.

In my comment I asked if anyone or any audio software out there has worked with Multiple-Pass waveforms... does anyone use such a technique? That is - digitally recording the playback of a single vinyl record two or more times, then using software to automatically synchronize the resulting multiple waveforms together, then detect random pops, clicks, and crackles from one pass and replace them with the synchronized audio at those precise moments from one or more of the other passes, to obtain a greater overall signal-to-noise ratio than one recording on its own.

Please allow me to quote myself from Mr. Hacker's blog comments section:

Quote from: camroncamera
My background is in visual imaging, more than it is working with audio, and one strategy employed with digitizing analog elements (say, scanning photographic slides or negatives) is called multipass scanning. Basically, the film scanner will scan a single film frame two, four, eight times, etc. (or however many passes you can wait around for) and combine the multiple passes back into one single image with increased image data and reduced noise. In this way, the consistent image data is reinforced and retained, while the analog noise normally introduced by the scanning equipment is rejected. (This is not dirt and dust removal or “film grain removal”, but merely a way to get the truer image from analog to digital).

So my thought is, does anyone (or any software) employ multipass recording of vinyl to combine the multiple waveforms of a single album or single track?  My thought is that each static-induced click or crackle would be different with each playing of the vinyl, and that by re-ripping the vinyl two or three times you could effectively combine the data from all these passes into a single waveform with superior signal-to-noise ratio than any one pass on its own. Software could automatically sync the multiple waveforms and remove any particular pop from one pass and replace it with music from another pass where there was no pop at that spot. Seems to me this would work for random pops and clicks, but obviously not on records with scratches or dirt causing the same noise regardless of the number of passes. Another very obvious drawback is that each record must be played and recorded 2 or more times, making a very time-consuming project take even longer.

But it seems to me that for very special records, or ones with particularly bad noise, this may be a useful strategy that would maximize the audio fidelity wherever possible, instead of diminishing it by covering up the flaws. I hope this has made some sort of sense :)

Please forgive me if this Multi-Pass concept is already a feature of Vinyl Studio, as I have not yet downloaded the trial (though I did read through the software home page, and performed a cursory search through this forum). I was surprised that a Google search did not bring any results for me with regard to this being done with any other audio software - and perhaps there is good reason, if this technique has already been tested and abandoned in the past.

Thank you for your input!

Title: Re: Combining Multi-Pass Waveforms
Post by: Paul Sanders (AlpineSoft) on February 24, 2013, 12:28:37 pm

No, VinylStudio doesn't do anything like that, sorry.  I'm not sure it would help in any case.  The clicks and pops are on the disc itself, and hence in a fixed position relative to the music.
Title: Re: Combining Multi-Pass Waveforms
Post by: camroncamera on February 26, 2013, 08:48:40 am

No, VinylStudio doesn't do anything like that, sorry.  I'm not sure it would help in any case.  The clicks and pops are on the disc itself, and hence in a fixed position relative to the music.

Thank you for the fast reply! I can completely understand what you are saying about noise which plays identically with each playback due to embedded dust and physical damage to the groove of the vinyl. I would expect, however, that crackle due to static, as well as noise from loose dust (especially if cleaned or otherwise disturbed between playbacks) would occur on a random basis?

Perhaps another way to take advantage of this sort strategy would be combining the waveforms from two different physical records (of the exact same pressing), since the embedded dirt and resulting clicks and pops would not repeat in the same positions, except when as a result of the pressing itself.  Flutter, wow, and minute speed playback variations would probably make perfect synchronization between multiple waveforms throughout the length of playback a challenge, but I suspect that software would make it possible to force the sync throughout.

Anyway, just throwing some ideas out there, thanks again for listening :)