Very Computer

by **Dick** » Thu, 26 Jun 1997 04:00:00

Hi folks

First let me say that if this question is inapropriate for group then I
apologise in advance and shall trouble you no more. I am not an expert (or
even as much as a novice) on DSP but it is the best lead I have on my area
of interest.

What I want to know is if there is any software or hardware product for the
PC available that uses DSP (I suspect) to filter unwanted noise and
crackles from audio recordings (on vinyl) after sampling and before writing
the tracks to CD.

I ask this question as a private record collector, and not from a company
or organization with large financial resources so any suggestions would
have to be AFFORDABLE.

I know such equipment exist because I remember seeing it on TV years ago.

Sorry to trouble you

Richard

by **Chris Bo** » Fri, 27 Jun 1997 04:00:00

>What I want to know is if there is any software or hardware product for the
>PC available that uses DSP (I suspect) to filter unwanted noise and
>crackles from audio recordings (on vinyl) after sampling and before writing
>the tracks to CD.

Cedar Audio in Cambridge, UK, have systems to remove hiss and crackle
from vinyl recordings. It may be worth calling them in case they have
some older systems that are less expensive than the posh rack mount
stuff. I believe the algorithms to do this are the result of many
years' research and are proprietary. The systems I have seen use
general purpose DSP (Lucent DSP32C) to do this.

I have details if you are interested.

Chris Bore
:-)
--
Chris Bore
BORES Signal Processing
Fordwater
Pond Road
Woking
Surrey GU22 0JZ
England

Tel: 01483 740138
Fax: 01483 740136

Web: http://www.bores.com

by **Stephan M. Sprenge** » Fri, 27 Jun 1997 04:00:00

We have a software which uses a Neural network approach to remove noise
without the unwanted side effects the other systems have. See

http://www.prosoniq.com/studio.html

for details. There only is a Mac version available at the time but we
are currently porting the software to PC, mail me if you wish to have
more info.

Kind regards

Stephan
--

======================================================================

http://www.prosoniq.com
Director, Research & Development
Prosoniq Products Software GmbH, Audio Research & Development
Technologiefabrik Karlsruhe, Germany
======================================================================

by **Andrew Reil** » Fri, 27 Jun 1997 04:00:00

Quote:> What I want to know is if there is any software or hardware product for the
> PC available that uses DSP (I suspect) to filter unwanted noise and
> crackles from audio recordings (on vinyl) after sampling and before writing
> the tracks to CD.

I remember seeing a stand-alone box from Cambridge Research
(?) a year or so ago that did this. Perhaps there are PC
based systems available now.

You should know that if it is real noise (Gaussian or
similar), white or nearly so (eg. tape hiss), then there is
very little that can be done. Perhaps perceptual filtering
can help. Much better results can be had for click removal
from records, because you can do things like correlate
multiple examples of the click as the track passes the
scratch multiple times, and because the clicks tend to have
a recognisable shape. There are papers on the subject, so I
suppose software has been written.

If anyone can point to something generally available, I'd be
interested too.

--
Andrew

"The question of whether a computer can think is no more interesting
than the question of whether a submarine can swim" - Edsgar W. Dijkstra

by **richard van hoese** » Sat, 28 Jun 1997 04:00:00

Quote:> ..I suppose software has been written.

> If anyone can point to something generally available, I'd be
> interested too.

at least two software packages that have options
for both noise removal and clicks/pops eleimination
come to mind:

- sound forge 4.0b with the noise reduction plugin
(the plug-in demo includes a bare bones sound forge)
demo available at:
http://www.sfoundry.com/pages/demos.htm#4.0b updates

- dart
demo available at :
http://www.midi-classics.com/p4126.htm

...they both seem to do a reasonable job.

richard.

by **Jason Moncrie** » Sat, 28 Jun 1997 04:00:00

> You should know that if it is real noise (Gaussian or
> similar), white or nearly so (eg. tape hiss), then there is
> very little that can be done. Perhaps perceptual filtering
> can help.> Andrew

> "The question of whether a computer can think is no more interesting
> than the question of whether a submarine can swim" - Edsgar W. Dijkstra

Good Lord. Pioneer (or perhaps it was someone else. Check your last
three months of Audio magazine) now builds a stand-alone cassette deck
designed with a DSP to do just that, and sells it for (as I recall)
under $500.

The general gist as near as I can tell is that the deck samples,
separates the signal into frequency ranges, runs an adaptive filter in
each range (LMS or something better), then sums the bands and sends the
signal to the DAC.

Great for hissy or noisy tapes, useless for pops on records.

-jmm

by **Ludger Solba** » Sat, 28 Jun 1997 04:00:00

writes:

Quote:> You should know that if it is real noise (Gaussian or
> similar), white or nearly so (eg. tape hiss), then there is
> very little that can be done.

Don't think so. The orthogonality property of white noise with
respect to any other signal definitely helps in separating it
from the rest. Narrow clicks are also not too difficult, since
they are approximately mutually orthogonal as well. More signi-
ficant difficulties arise when the noise is coloured or when
the clicks are spread in time.

Regards,

Ludger.

--

----------- Ludger Solbach, Distributed Systems Department -----------
| Technical University of Hamburg-Harburg, Germany |

----------------- http://www.ti6.tu-harburg.de/~ti6ls/ -----------------

by **Christopher Wear** » Sat, 28 Jun 1997 04:00:00

> You should know that if it is real noise (Gaussian or
> similar), white or nearly so (eg. tape hiss), then there is
> very little that can be done. Perhaps perceptual filtering
> can help.> Andrew.

There are numerous techniques for removing noise, gaussian distributed
or not (tape noise is not white by the way). Since this type of noise
is uncorrelated, it can be separated from the signal with varying
degrees of success by taking advantage of this fact. Downward spectral
expansion and linear prediction are two examples.

Chris Weare
Arboretum Systems

by **Tom Parke** » Sat, 28 Jun 1997 04:00:00

> > What I want to know is if there is any software or hardware product for the
> > PC available that uses DSP (I suspect) to filter unwanted noise and
> > crackles from audio recordings (on vinyl) after sampling and before writing
> > the tracks to CD.

You may want to try CoolEdit. It allows you to highlight a portion of
the waveform on the screen that contains noise, then it can filter the
noise that it sampled from the recording.

Tom

by **Dave Come** » Fri, 04 Jul 1997 04:00:00

There is a nice Windows based package called Cool96 that is made for
audio processing. IMHO it's excellent shareware. The registerd version
has tools to interface to C programs and has FFT processing built in.
It may be what you are looking for. The company is "Syntrillium"
and the URL is http://www.syntrillium.com.

Hope this helps,

Dave Comer

Very Computer

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dsp and filtering audio signals - a silly question??

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dsp and filtering audio signals - a silly question??

dsp and filtering audio signals - a silly question??

dsp and filtering audio signals - a silly question??

dsp and filtering audio signals - a silly question??

dsp and filtering audio signals - a silly question??