LISTSERV mailing list manager LISTSERV 16.0

Help for ARSCLIST Archives


ARSCLIST Archives

ARSCLIST Archives


ARSCLIST@LISTSERV.LOC.GOV


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Proportional Font

LISTSERV Archives

LISTSERV Archives

ARSCLIST Home

ARSCLIST Home

ARSCLIST  February 2006

ARSCLIST February 2006

Subject:

Re: Cassette obsolescence - digitizing standards

From:

Bob Conrad <[log in to unmask]>

Reply-To:

Association for Recorded Sound Discussion List <[log in to unmask]>

Date:

Tue, 21 Feb 2006 19:27:51 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (130 lines)

Dave Bradley wrote:

>> OK...so am I understanding correctly that you are transferring 
>> through your converter into your computer at 16bit, but then 
>> importing it into ProTools for 24bit?
>>
>> If this is the case, you're not "enhancing" the sound quality, but 
>> just using some kind of algorithm(s) in order to get a more complex 
>> file - information that was added, by the way, and has nothing to do 
>> with the original.
>
>
> That's not entirely accurate. In fact, it's quite INaccurate.
>
> Any adjustments made to the sound file will result in a mathematical 
> calculation which is never done as simple addition or subtraction. The 
> simple process of even just boosting the level by 3 db results in a 
> multiplication process that when fed 16 bits of data will result in 
> more than 16 bits of final calculation in the form of a decimal.
>
> Some people would simply say truncate that result back to 16 bits and 
> you're accurate enough for government work.
>
> The problem with that is that any additional work done on the file 
> will also result in a similar calculation.  Let's say this time it's a 
> bit of hiss reduction, and maybe some EQ boost to the 1KHz to 3KHz 
> band.  If each of those is working with the 16 bit PLUS decimal value, 
> then each calculation will result in a more accurate representation of 
> the final value. Only when all processing is done should you drop back 
> to 16 bits through whatever process, truncation, dithering, noise 
> shaping, etc. that you feel is appropriate.
>
> If, on the other hand, you leave the file as 16-bit, each calculation 
> done for each adjustment you make will leave an error which the next 
> calculation will amplify until you start to get noticeable problems.
>
> A totally made up example which gets the idea across could be as follows.
>
> Initial value 179.
> Your first calculation is your initial value * 0.5749.
> Your second calculation is the result of your first value * 4.7768.
> Your third calculation is the result of your second value * 2.48.
> Your fourth calculation is the result of your third value * 1.17.
> Your final value is the result of the fourth calculation brought back 
> to 16-bit world.
>
> If you start at 16 bit and stay at 16 bit through this entire process, 
> then here's what you get.
> First calculation (179 * 0.5749) results in 102.90710000 which is 
> immediately truncated to 102 so it will fit entirely in the 16-bits 
> which has no room for the decimal value. No, it won't round it up to 103.
> Second calculation (102 * 4.7768) results in 487.23360000 which is 
> immediately truncated to 487 so it will fit entirely in the 16-bits 
> which has no room for the decimal value.
> Third calculation (487 * 2.48) results in 1207.76000000 which is 
> immediately truncated to 1207 so it will fit entirely in the 16-bits 
> which has no room for the decimal value. No, it still won't round it 
> up to 1208.
> Fourth calculation (1207 * 1.17) results in 1412.19000000 which is 
> immediately truncated to 1412 so it will fit entirely in the 16-bits 
> which has no room for the decimal value.
> Your final value is 1412 after 4 simple adjustments to the audio data.
>
> Now, if you take that 16-bit file and import it as 24-bit, do your 
> calculations and then truncate, dither, or otherwise produce a 16-bit 
> final file, you'll notice the value changes drastically.
> First calculation (179 * 0.5749) results in 102.90710000 (the extra 8 
> bits holding the value to the right of the decimal place).
> Second calculation (102.90710000 * 4.7768) results in 491.56663528.
> Third calculation (491.56663528 * 2.48) results in 1219.08525549.
> Fourth calculation (1219.08525549 * 1.17) results in 1426.32974893.
> Let's assume you do a simple truncation at this point to go back to 
> 16-bit. That value is now 1426, whereas when you worked strictly in 
> 16-bit it turned out to be 1412.
>
> Hmm, which one was more accurate?
>
> You'll notice that in the "stay in 16-bit" example above, the 
> truncated results each time were small enough that they certainly 
> weren't using the full 16 bit capabilities of the digital sample.  
> (102, 487, 1207, 1412) The first number, 102, could be represented in 
> 6 bits, the second number, 487, could be represented in 9 bits, the 
> third number, 1207, could be represented in 11 bits, and the fourth 
> number, 1412, could be represented in 11 bits. So it's obvious that 
> we're not dealing with audio that is pressing the limit of 16-bit 
> sampling. The argument that because cassette tape is not up to CD 
> quality so any processing can remain in the 16-bit realm has just now 
> been invalidated.
>
> You MAY be able to capture all of the existing audio from a cassette 
> in 16-bit sampling, but NEVER do any processing in 16-bit. Do it in 24 
> or even 32 bit and then drop your final result to 16-bit through 
> whatever method you wish and you'll end up with a far more accurate 
> digital audio file than if you allowed all those computational errors 
> to creep in.
>
> (And in case you didn't notice, the difference between 1412 and 1426 
> is NOT just a small rounding up or down error.  It's 14 values 
> different.)
>
>
>
> -----------------
> Diamond Productions
> Preserving the past for the future.
> Dave Bradley   President
>
>

I'm sorry to say that I do not agree with you at all.  Your calculations 
look very impressive, but as you said, the examples cited are totally 
made up.  And there seems to be numerous factors not included in the 
equations (huge increase in digital noise and relative distortion from 
the original 16 bit file being upsampled to 24 bits; and one major 
oversight, that is, dithering [or truncating] down a 24-bit file to 
16-bits creates aliasing and quantizational errors [ie dithering 
noise]).  And this is regardless of what software or noise-shaping 
algorithms used.  Why do all this to audio from a cassette that most 
likely already suffers from noise/hiss problems?  Oh, and last but not 
least, my ears can pick up the other problems that this scenario creates 
-- audible digital artifacts.  The only way to avoid having to deal with 
this mess is to do the job right in the first place and make the 
original transfers in 24 bit.  It might be best for the original poster 
to invest a few dollars in obtaining an Alesis Masterlink.

One man's opinion.

Bob Conrad
Fort Lee, NJ

Top of Message | Previous Page | Permalink

Advanced Options


Options

Log In

Log In

Get Password

Get Password


Search Archives

Search Archives


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

November 2019
October 2019
September 2019
August 2019
July 2019
June 2019
May 2019
April 2019
March 2019
February 2019
January 2019
December 2018
November 2018
October 2018
September 2018
August 2018
July 2018
June 2018
May 2018
April 2018
March 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
August 2017
July 2017
June 2017
May 2017
April 2017
March 2017
February 2017
January 2017
December 2016
November 2016
October 2016
September 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
January 2016
December 2015
November 2015
October 2015
September 2015
August 2015
July 2015
June 2015
May 2015
April 2015
March 2015
February 2015
January 2015
December 2014
November 2014
October 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
August 2013
July 2013
June 2013
May 2013
April 2013
March 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
May 2012
April 2012
March 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
September 2010
August 2010
July 2010
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
December 2009
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
February 2007
January 2007
December 2006
November 2006
October 2006
September 2006
August 2006
July 2006
June 2006
May 2006
April 2006
March 2006
February 2006
January 2006
December 2005
November 2005
October 2005
September 2005
August 2005
July 2005
June 2005
May 2005
April 2005
March 2005
February 2005
January 2005
December 2004
November 2004
October 2004
September 2004
August 2004
July 2004
June 2004
May 2004
April 2004
March 2004
February 2004
January 2004
December 2003
November 2003
October 2003
September 2003
August 2003
July 2003
June 2003
May 2003
April 2003
March 2003
February 2003
January 2003

ATOM RSS1 RSS2



LISTSERV.LOC.GOV

CataList Email List Search Powered by the LISTSERV Email List Manager