My understanding of "normalize" is that it means multiplying every sample
in a file by some coefficient calculated to set the largest sample in the
file, i.e. the peak amplitude, to a specific point, such as -13 dBfs.
However, lately I've seen "normalize" used to mean adjusting the *average*
amplitude, which involves more complicated calculations and runs the
risk of peak clipping or worse. So it's important to establish which sense
of "normlize" we are speaking of.
Rob
--
Я там, где ребята толковые,
Я там, где плакаты "Вперёд",
Где песни рабочие новые
Страна трудовая поёт.
On Thu, 1 Nov 2018, Robert Jeffares wrote:
Gregory,
it will work
in that your /var/snd/ files will all be normalised by sox to -5.
However the -13 level is a better option than bumping the audio file level
up.
For a number of reasons the -13 level was chosen to allow 'headroom' for the
bits of audio that overshoot 0vu.
In digital audio, overshoots cause lots of instant distortion. I have a
couple of Lexicon sound devices which are excellent when I allow headroom but
show no mercy to the inevitable peaks in programme content.
If you need to increase the gain from the sound card out to the desk, it's
relatively easy to install an amplifier which takes the sound card output and
boosts it by about 20db. In our situation we took unbalanced out of the PC
card and deliver balanced at +4 to a limiter which then connects to the
transmitter.
If you are running the RD out through a board you may need slightly less.
I don't think you can buy a box that does the job. Our ones are an OpAmp and
some components in a box with a 5v power supply.
regards
Robert Jeffares.
On 1/11/18 8:43 AM, Gregory Avedissian wrote:
We've had a problem with broadcast volume levels, and we've settled on
using a normalization level of -5 when importing into the library. The
engineer has tweaked the transmission as best he can without bothering the
nearby airport.
There are still a bunch of carts that were imported at -13.
Someone started re-importing them manually to raise the norm level. I told
them I could script it and do the whole library automatically. Now I need
to deliver.
Is it safe to do something as simple as having the script go to /var/snd
and run:
for i in *.wav ; do sox --norm=-5 "$i" /tmp/"$i" && cp /tmp/"$i" "$i" ;
done
Oh yeah, there will be rm /tmp/"$i" in there, too. Just noticed that.
I ran a quick test, and it seems to work. Seems too easy. Am I missing
something?
Greg
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