Tape Wobble

[sus4chord]

Over on another forum I frequent, a person asked:

Does anyone know ( Particularly Mac ) of any software
that can remove wobble from a music cassette ? I've got quite a lot of tapes, many are in poor shape.

Is this something DC7 can do, and if so, what are the basics for accomplishing this?

[Craig Maier]

I am not familiar with the term "wobble". I know of speed shift, wow, flutter, and dropouts associated with cassettes. Diamond Cut can deal with speed shift and dropouts, but not wow or flutter.

[sus4chord]

Hi, Craig -

I'm pretty sure he means wow and flutter, possible stretched or shrunk tape over time, as well as in some cases, cassette tapes that were eaten partially by tape players, but still have content on them. He received a bunch of tapes from a relative and is interested in trying to get them to sound right.

Thanks for the feedback. I didn't think there was a good solution for this type of thing, but I thought I would ask the question.

[Dan McDonald]

With shrunken/stretched tapes, or those recorded with dying batteries, he can use the speed change to fix them up. I've used that fairly often. With dying batteries, sometimes it's a linear change and sometimes it's nonlinear. I usually just get the best estimates as to how far off it is at the beginning and how far off it is at the end, and see if a linear change works, then make alterations after that if there were other problems.

Dan

[DJBohn]

I've always wondered if a high end pitch correction program, such as like professional singers would use, could be set up to correct tape flutter of a wide band recording. I've heard some non-streched tape recordings that had simply awful flutter, such as done on an old & cheap portable rim drive R2R.

[sus4chord]

I think the problem with pitch correction software (which I've used to good success before) is that it generally wants a solo melodic line. It can match your voice or a single instrument against the target frequency and bring it in line, but throw a chord or a while orchestra at it, and it's just going to get really confused.

[Craig Maier]

No Reference signal, no correction FM Correction possible

Yes, the problem with correcting wow and flutter is finding a solid reference signal on the source material. Without that, it is impossible to wrap a control loop around the system in order to correct.

There was a protracted discussion about this topic about a year ago initiated by a person who claimed to have figured out how to correct this kind of problem.

The issue was that the genteleman advocated a process which violated all of the laws of physics and mathematics that I am aware of, and thus could not have possibly worked, (except in the deep cravices of his mind).

[Dan McDonald]

the genteleman advocated a process which violated all of the laws of physics and mathematics that I am aware of, and thus could not have possibly worked.

That was that Einstein guy, right Craig?

Dan

[Craig Maier]

The guy I am referring to was more like Mr. MaGoo. He threatened to sue us after I highlighted the the flaws in his math. A proof consisting of "trust me, it works" does not hold up in the academic world of peer review. What a joke that was!

[sus4chord]

I remember that thread; it wasn't pretty.

[IASForensics]

References to Wow and Flutter papers and services

If you are interested in some serious reading, a paper on the subject of wow and flutter correction was published by AES.org a while back. The link is: http://www.aes.org/e-lib/browse.cfm?elib=12870

Also, there is a company that does provide the service of removal of wow and flutter from recordings:

Jamie Howarth, Plangent Processes, http://www.plangentprocesses.com


I've asked them if they would do a VST or DirectX plugin and the answer was no because the process is not as simple as that.

-Jonathan

[Craig Maier]

Quoting IASForensics:

"Also, there is a company that does provide the service of removal of wow and flutter from recordings:

Jamie Howarth, Plangent Processes, http://www.plangentprocesses.com


I've asked them if they would do a VST or DirectX plugin and the answer was no because the process is not as simple as that."

-Jonathan

------------------------------------------

Hi Jonathan,

Mr Howarth is the guy who made the claims on this website that are referred to in this thread. The reason that he would have replied "no because the process is not as simple as that" is simply because the mathematical principles that he described here are completely flawed. If it could have been done, it would have been done.

It is as simple as that.

Craig

[Marc Hildebrant]

Craig,

Quite a bit of information out on the net with regard to the Plangent abilities to remove tape distortion.

Are the threads available here to read about the technical details ?

Regards,
Marc

[Craig Maier]

Hi Marc,

What he claims to be able to do is to remove wow and flutter, not tape distortion per se. After I revealed the "taboo" here on this site through a protracted public debate, he threatened to sue Diamond Cut Productions for questioning his technology.

So, I told him to sue us (he never did) and I removed all of the posts from the forum. What he is attempting to do violates the principles set forth by the Nyquist Criteria for control loop (phase lock or otherwise) stability and sample theorems requirement for a certain amount of bandwidth to correct a signal having certain frequency content. In short, IMHO, this is snake oil.

Craig

[Marc Hildebrant]

Craig,

O.K. then. Sounds like it's wise to just remove the postings (as you did).

Regards,
Marc