In article , Don Pearce
wrote:
On Fri, 10 Feb 2012 17:21:06 +0000 (GMT), Jim Lesurf
wrote:


I've been experimenting with 'sox' to deemphasise audio CD data, and
the flexibility of sox set me wondering about using it to eq old EMI
recordings that sometimes have an edgey quality to the strings, and
lack low bass because of their old fear of bass causing 'groove
jumping'. Not experimented yet, but wondered if anyone else has had a
play with this.

Jim

Don't know what sox is,

http://sox.sourceforge.net/Docs/Features

The above gives a summary of sorts. But basically it is a command for doing
all kinds of things/with to audio files. I use it mainly for simple
conversions like Wave = Flac or changing sample rates or depths. But more
recently I've used it to deemphasise 'eq'd audio CD tracks. e.g. by using

sox infilename.wav -b 24 outfilename.flac deemph

It will take an input file (wave) ripped as 44.1k/16 and generate a flac
output that has had the Red Book deemphasis applied. The '-b 24' gets it to
output the flac as 24 bits per sample to avoid any losses that might arise
when dithering down the output back to 16 bit.

Since then I've also experimented with doing things like

sox infile outfile equalizer 3k 2o -6.0 bass +6.0

[N.B. that is '2 followed by a lower case 'Oh', not a zero as it means
'octave'.]

which would apply a 2nd order band filter centered at 3kHz that is 2
octaves wide with a dip of -6dB at 3k and also apply a 'baxadall' bass lift
rising to 6dB at LF. You can actually chain a series of such effects if
required. Or have complex effects specified by a script file. You can
define the filters by time-domain or FFT if required. Or biquad
coefficients, etc, so it is (bewilderingly!) flexible.

Being a command util it is then easy for me to write a simple drag-and-drop
wrapper or use it for batches of files if required.

The real question, though, is what - if any - such alterations may be an
'improvement' when it comes to something like the more 'scratchy' old EMI
recordings.

Slainte,

Jim

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