linuxaudio.org

On Fri, Dec 24, 2010 at 06:51:18PM +0100, Jörn Nettingsmeier wrote:
> On 12/24/2010 06:07 PM, Q wrote:
> > Out of interest, how high can intersample peaks get above the highest

quoted text
> > peaks in a file?

>

> imagine the positive half of a sine wave, so that two consecutive

> samples representing the very top of the wave are at 0dBFS. it is clear

> that between those samples, the real peak value of the sound must be

> higher than 0dBFS, and the reconstruction filter will see this higher

> value. that means unless your analog stage has headroom for this, it

> will clip. the higher the frequency, the higher above full scale those

> inter-sample peaks can be.

In theory it could be any value. In practice it's limited by the lenght

of the antialiasing filter. You get the maximum output for a series of

samples at max amplitude (+ or - 1) and matching the sign of the IR of

the filter at half a sample delay.
For example, if '+' means a sample of +1, and '-' a -1, then the

sequence of 20 samples:
 -+-+-+-+-++-+-+-+-+-  
will produce of peak of more than 8 dB above FS.
It's very unlikely to get such a sequence with natural sounds,

but quite possible with synthetic signals or when using agressive

mastering techniques.
Ciao,
--

FA
There are three of them, and Alleline.
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