Re: [LAU] Gain and clipping wav -> lame

On Thu, Jul 25, 2013 at 04:14:20PM -0400, Martin Cracauer wrote:

> Is there a rule of thumb how many db less I should give music
> to avoid this?

Depends entirely on what you are trying to do, what sort of
signals/music you have, how the clips are going to be used,
and where you stand in the 'loudness wars'.

'Acoustic' music has a peak/RMS ratio of around 20 dB.
The EBU standard means to aim for an average RMS level of
-23 dB. Most popular music productions try to have a much
higher average level, and hence a lower peak/RMS ratio,
something like 10 dB, or 6 dB for the more agressive ones,
and as low as 3 dB if the target audience is the braindead.

OTOH, if your clips are e.g. unprocessed drum samples, you
could have a peak/RMS ratio that is much higher than 20 dB.
So it depends, use your judgement.

> What would be the value for pink noise starting at 40 Hz?

Impossible to say. Gaussian noise (analog noise is Gaussian)
has in theory an infinite peak/RMS ratio. In practice it will
be limited of course.

To get an idea of this, you could measure the pink noise
provided by e.g. japa with jkmeter (which shows RMS and peak).
The RMS value is -20 dB. If you wait long enough, the peak
memory can take any value, there is no limit.

In practice, if one or few samples per second get clipped
you won't notice.

 
> Is there a way to hook up ebumeter to just an audio file or a stream
> not associated with real time? It seems to come in a jack package only.

If you have ebumeter installed, try

   ebur128 --full --lufs filename.wav

The ebur128 program is included in the source distribution
of ebumeter, I don't know if it's available in binary packages.

Ciao,

-- 
FA
A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)
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