Definitions of nomalize, clipping, limiting and compression
Per Stromgren
very much a discussion of what the words mean. In order to put that
particular discussion to rest I invite the parties to come to an
agreement about the words. I propose the following descriptions of
these often discussed words:
*** Normalize - to scale an entire sound file in order for its loudest
sample to hit full scale (0db FS), or a tiny bit less. This is
performed by first looking up the loudest sample, and then multiply
all samples by the (constant) factor that takes the loudest up to a
fraction under 0dB FS. The sound file's average level is not taken
into account at all when calculating the gain, only its loudest
sample. The effect is like turing the wolume knob up.
*** Clipping - what often happens to a signal that is too loud for a
system. An amplifier can't put out more than plus and minus rail
voltage; any signal louder than that is "clipped" to this voltage,
which sounds awful. The same thing happens when you hit 0dB FS in a
digital system; it can't put out more than "all bits on" (not always
to be taken literally). This maximum level is sometimes called clip
level.
*** Limiting - what you perhaps want to do to a signal in order for it
to fit under your systems clip level, but not being clipped. It can be
accomplished by adjusting the gain for the signal, when it is to reach
clip level. This can be done by hand or automatically. In any case you
will get a compression of the signal.
*** Compression - A non-linear transpose function where the gain is a
function of the signal level. Most often it is used to amplify soft
passages more than loud ones to avoid the soft ones to drown in noise,
but is also used as an effect in modern music. Compressing is also
used as part of other signal handling, Dolby NR for instance. The
effect of compression on music is that it sounds louder, beacuse its
average level has gone up.
Feel free to adjust the above in order for you to agree!
Per.
Benny354
limiting, could you clarify
Robert Rowton
>I know all of these except compression, I thought compression was the same as
>limiting, could you clarify
Hello,
Limiting, soft-limiting anyway, is reducing the gain of high-level
passages above a set threshold, whereas compression also includes
increasing the gain of low-level passages below a set threshold. The
terms are often used interchangeably.
Benny354
does?
dmi...@spamblock.demon.co.uk
> I know all of these except compression, I thought compression was the
> same as limiting, could you clarify
Limiting is a special case of compression where for every db above the
threhold level, the gin is reduced by 1db. In general compression
you often reduce the gain by less then the amount the signal is above
threshold.
Limiters are also (usaually) charicterised by a very fast attack time,
and in some cases actually use a delay line to allow the gain control
logic to look a few ms ahead of the signal so that the gain can be
reduced before the signal hits threshold.
A limiter is a compressor, but a compressor is not necassarily a limiter.
Regards, Dan.
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dangling entity
> I know all of these except compression, I thought compression was the same as
> limiting, could you clarify
Limiting is like the more aggressive cousin to compression.
Compression can be more progressive as you reach the full effect,
while limiting tries to remain more faithful to the signal until you
reach a certain threshold, then CHOP! ...sort of like that.
Naturally, there will be varied degrees of limiting.
dangling entity
> Thanks, so compression can also be used to do the opposite of what limiting
> does?
Not really, AFAIK. An "expander" would be used to undue a "compressor".
Geoff Wood
"Benny354" <benn...@aol.com> wrote in message
news:20030630122524...@mb-m07.aol.com...
> I know all of these except compression, I thought compression was the
same as
> limiting, could you clarify
Limiting is generally a heavy amount of compression invoked at a high
threshold with the express purpose of preventing overloading in a subsequent
stage.
geoff