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Good show, Tom!

I've had some discs here made on a home recorder and tried 
intermittently, and unsuccessfully, to get a complete transfer with 
increasingly unconventional pickups, groove depth (or lack of it) being 
the issue, so I too hope that surface scanning will come to the rescue. 
In the mid-80s, a very august person from BBC Research Department told 
me that hiss removal was in the realms of science fiction, so we may hope!

On 25/10/2013 13:18, Tom Fine wrote:
> Hi Ted:
>
> Much better!
>
> The wonders of modern DSP in careful craftspeople's hands!
>
> The next frontier will be figuring out how to grab the just musical 
> content out of a noisy grooved disk and then un-do the problems of 
> groove distortion and disk wear. I hope Carl Haber's work leads there 
> -- scan the groove and then come up with some kind of Photoshop-like 
> algorhythm to "heal" groove wear and the material on the groove 
> surface that produces playback noise (I'm assuming that comes down to 
> rough-surface shellac, which would need to be differentiated from 
> minute lateral changes in the groove, ie soft-dynamic music content). 
> I am optimistic that such a system will emerge in my lifetime. Imagine 
> few-dozen-dollar software that enables you to scan your 78RPM disks on 
> a high-resolution flatbed, then "heals" the ravages of time and the 
> problems with the original shellac compound and saves a clean,crisp 
> audio file to your hard drive.
>
> -- Tom Fine
>
> ----- Original Message ----- From: "Ted Kendall" 
> <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Friday, October 25, 2013 7:56 AM
> Subject: Re: [ARSCLIST] Advice needed on removing / minimizing tape 
> bleed-through
>
>
>> Tom - is this better?
>>
>> I couldn't agree more - some tapes we only get one good shot at, and 
>> the aim has to be to preserve as much information as possible.
>>
>> Cedar Retouch (now much imitated) is indeed a sort of audio photoshop 
>> with a spectral display - time is the x-axis, frequency the y-axis 
>> and amplitude the z-axis, done with colour. The things you can fix 
>> with it (and the mess you can make if you are careless) are nobody's 
>> business - dropouts, bumps, clicks, pre and post echo, some 
>> distortions, etc, etc. I like it, use it all the time, and I paid for 
>> it!
>>
>> The nice thing, as I've said, is that you can pinpoint the offending 
>> noise in time and frequency, so the amount of original material you 
>> modify is minimised - and often the print is greatest at two or three 
>> spot frequencies. If you take those bits out, the ear can't hear the 
>> rest.
>>
>> On 25/10/2013 11:53, Tom Fine wrote:
>>> Ted, any chance you could modify your comment style to put them up 
>>> top or in-line with the previous text? Sometimes your comments are 
>>> many page-downs away, at the bottom of a long thread.
>>>
>>> I have to agree with Ted on this point:
>>> "To use agressive and irreversible techniques on an analogue 
>>> original is surely to be discouraged when other techniques are 
>>> available."
>>>
>>> A tape with bad print-through is more likely than not to be old and 
>>> maybe there are limited opportunities left to transfer it without 
>>> major playback issues. So, a clean, high-resolution transfer should 
>>> be made and then you can use copies of the digital file to try DSP 
>>> remedies. I do doubt that analog remedies would be any more or less 
>>> effective than DSP circa 2013.
>>>
>>> I did suggest in my first reply that one could attempt analog 
>>> solutions to the problem, but I've changed my mind on that. I can't 
>>> think of an analog tool that would work markedly better from today's 
>>> sophisticated DSP "remedy" software. And the many playback passes 
>>> required for experimentation might be very bad for an old source tape.
>>>
>>> Another thought that occured to me was try working in one of the 
>>> spectral programs, like Sony Spectral Layers. I haven't had time to 
>>> figure this kind of method out yet, but plan to investigate. I'm 
>>> suggesting this because I noticed in an AES presentation that 
>>> spectral-display information was used to show out artifacts of 
>>> ancient splices were rendered inaudible without effecting the music 
>>> content. I assumed that a spectral editor was used to identify and 
>>> "heal" the splice artifact. Perhaps the Cedar program Ted 
>>> recommended is just such software?
>>>
>>> -- Tom Fine
>>>
>>>
>>> ----- Original Message ----- From: "Ted Kendall" 
>>> <[log in to unmask]>
>>> To: <[log in to unmask]>
>>> Sent: Friday, October 25, 2013 5:32 AM
>>> Subject: Re: [ARSCLIST] Advice needed on removing / minimizing tape 
>>> bleed-through
>>>
>>>
>>>> On 25/10/2013 05:40, John Chester wrote:
>>>>> At 10:51 PM 10/24/2013, Malcolm Rockwell wrote:
>>>>>> There may not be a major problem here. What has printed through 
>>>>>> is the audio from the next layer of tape, correct? With digital 
>>>>>> manipulation being what it is today it should be simple enough to 
>>>>>> grab the full volume layer of audio, attenuate it, flip the 
>>>>>> waveform and apply it "over" the printed through signal. There 
>>>>>> will probably be artifacts but if you fiddle with various 
>>>>>> parameters for a while, such as EQ, you will probably be able to 
>>>>>> find an acceptable solution to your problem. I'd apply this to 
>>>>>> softer passages and leave louder material well enough alone, though.
>>>>>> It's worth a try.
>>>>>> Comments?
>>>>>
>>>>> There are a number of problems to consider.
>>>>>
>>>>> First, the printed recording is not the same length as the 
>>>>> original.  The delay between original and print changes as tape 
>>>>> pack diameter changes.  Seems to me that for a tape which has been 
>>>>> stored tails out, the print is longer than the original.  (Delay 
>>>>> from original to print increases as tape pack diameter on the take 
>>>>> up reel increases.)  The original recording can be speed-shifted, 
>>>>> but you need to figure out how much to shift it.
>>>>>
>>>>> Second, the frequency response of the printing process is not 
>>>>> flat.  According to
>>>>> http://www.aes.org/aeshc/docs/3mtape/printthrough.pdf
>>>>> "The worst print-through occurs at a wavelength equal to 27 * C. C 
>>>>> is the total tape caliper in mils. For a typical 2
>>>>> mil mastering tape, the worst wavelength for print-through would 
>>>>> be about 12.6 mils. When running at 15 ips, this
>>>>> would be a frequency of about 1200 Hz."
>>>>> Note:  there's an error in their formula, as printed in the 
>>>>> on-line document.  It should read 2 * Pi * C.  But they're correct 
>>>>> that it's worst at about 1200 Hz.  This is confirmed by the 
>>>>> October 1980 JAES article "The Print-Through Phenomenon" by 
>>>>> Bertram, Stafford and Mills. It includes a graph of print-through 
>>>>> vs. frequency.
>>>>>
>>>>> BTW, this article also states that "print-through ... can be 
>>>>> reduced if [the tape] is repeatedly rewound.  The amount of print 
>>>>> reduction ...can reach as much as 7 dB." In their tests, this 
>>>>> required 6 rewindings.  "The rewindings should be consecutive with 
>>>>> an optimum storage time between rewindings to achieve maximum 
>>>>> reduction.  The optimum storage time may depend upon the 
>>>>> individual tape."
>>>>>
>>>>> Third, is the printing process linear or non-linear?  The 3M 
>>>>> document cited above says it's linear.  Camras, in the 1988 
>>>>> edition of "Magnetic Recording Handbook", says it's not, and that 
>>>>> the ratio of the original to printed signal varies with the level 
>>>>> of the original signal.  I think Bertram et al.  are saying it is 
>>>>> linear, but I must admit that I have not yet entirely digested 
>>>>> this long, complex article.  Hopefully it is linear, because 
>>>>> modelling a non-linear transfer function will not be much fun.
>>>>>
>>>>> So....  If the printing process is linear, the other problems seem 
>>>>> manageable.  But it will no doubt require a fair bit of fiddling 
>>>>> to get the cancellation signal lined up in time and amplitude with 
>>>>> each objectionable echo.
>>>>>
>>>>> -- John Chester
>>>>>
>>>> I routinely use Cedar Retouch for print-through problems, whether 
>>>> pre- or post-echo, and usually find that removing the two or three 
>>>> most prominent components is enough to push it back into the noise. 
>>>> To use agressive and irreversible techniques on an analogue 
>>>> original is surely to be discouraged when other techniques are 
>>>> available.
>>>>
>>>>
>>>
>>
>>
>