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3-12-3] How can I clean up the audio before recording?




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This article is from the CD-Recordable FAQ, by Andy McFadden (fadden@fadden.com) with numerous contributions by others.

3-12-3] How can I clean up the audio before recording?

(2000/12/02)

There are a variety of programs that can automatically remove pops, clicks,
and hissing from digitized audio. Few automated tools can do as good a job
cleaning up pops and other noise as an experienced person, however. If you
want to perform the transfer by hand, the following method has been
suggested for PC users with Cool Edit:

- Record directly into Cool Edit, using the highest possible input
level that doesn't exceed the maximum. You want to record 16-bit
stereo samples at 44.1KHz.
- In the "noise reduction" dialog, set FFT size to 8192, FFT precision
to 10, and #of samples to 96.
- Select a silent passage between songs or from the end of the record.
It can have some crackling but no huge pops. Set the noise level.
- Select the entire track and perform noise reduction at about 70%.
- Select the entire track and normalize it.
- Manually remove any big pops (easily located by zooming in to the general
area and switching to "spectral view" in the edit menu) by zooming in on
them and amplifying them to about 8%. You only need to select the
channel (left or right) in which the offending data occurs. If it occurs
across BOTH channels, you may get a better result by deleting that part
of the track and reconstructing it in such a way that it remains
smooth... if that's not possible, make one channel smooth and then
amplify the other to 8%.

Cool Edit optionally leaves a blob of data at the end of the .WAV file,
which is legal in the file format but not expected by some utilities. To
avoid this, make sure the "Save extra non-audio information" box isn't
checked.

Software that may come in handy:

GoldWave
http://www.goldwave.com/, a good audio editor (shareware).
Adobe Audition (formerly Syntrillium Cool Edit)
http://www.adobe.com/, fancy commercial audio editor.
Sound Forge
http://www.sonicfoundry.com/, fancy commercial product with
lots of plug-ins.
Clean! plus
http://www.steinberg.net/products/, designed for vinyl and tape xfers.
Algorithmix
http://www.algorithmix.com/, has a noise reduction program called
SoundLaundry.
DART and DART PRO
http://www.dartpro.com/, designed for audio restoration ("click
removal" and more).
DCart
http://www.diamondcut.com/, audio restoration.
Pristine Sounds 2000
http://www.alienconnections.com/, audio restoration.
Gnome Wave Cleaner
http://gwc.sourceforge.net/, audio cleanup under Linux.
Waves software (various)
http://www.waves.com/, fancy (and expensive) audio manipulation.
CD Wave
http://www.cdwave.com/, useful for splitting a single large WAV
file on track boundaries.
RIP Vinyl
http://www.ripvinyl.com/, similar to CD Wave.

Wave Repair, from http://www.waverepair.com/, is a WAV editor designed with
analog recording and click-fixing in mind. It's aimed at very flexible
manual repair with some helpful automation. If you'd like something
a little heavier on automation and a little lighter on manual control,
try Wave Corrector at http://www.wavecor.co.uk/.

Don't forget that CD audio is 16-bit PCM stereo samples at 44.1KHz, and
will chew up disk space at roughly 176K per second. Playing back large
sound files is difficult with simple-minded applications like the standard
Win95 sound player, because they try to load the entire file into memory
all at once. Windows Media Player should work fine. (Section (4-20)
has some other suggestions on this same topic.)

See section (3-3) for some tips on avoiding clicks when committing the
audio to CD.

If, for some reason, you'd like to record "live" to the CD-R instead of
recording to the hard drive first, see section (3-54).


 

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