On Sat, 25 Dec 2010 12:40:33 +0100 fons@xxxxxxxxxxxxxxx wrote: > On Fri, Dec 24, 2010 at 06:51:18PM +0100, JÃrn Nettingsmeier wrote: > > > On 12/24/2010 06:07 PM, Q wrote: > > > > Out of interest, how high can intersample peaks get above the highest > > > 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, Interesting. When I first started to use a digital recorder I used -6dBFS as my target value simply on a 'gut feeling' basis. Seems I wasn't so far out then. -- Will J Godfrey http://www.musically.me.uk Say you have a poem and I have a tune. Exchange them and we can both have a poem, a tune, and a song. _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
