Audio time-scale/pitch modification

Time stretching is a term used in modern audio technology and describes how to modify the playback speed of existing audio files without changing the pitch.

The opposite of time-stretching is the pitch change (fachsprachlich English pitch shifting ), in which only the pitch, but not the playback speed is changed. The mathematical basis for the two methods is often the fast Fourier transform.

Time-stretching and pitch changes may 'realistic' sound only within certain limits. Values ​​from about 15 to 20% deviation from original material to produce audible noise ( grain or Verhallungs artifacts ) that are partially used as an effect, but alienate the original place.

Radio stations set, inter alia, Time-stretching, in order to adapt songs the exact second the schedule (so, for example, songs end exactly at the beginning of news or traffic reports ).

Meanwhile recent methods allow an improved quality can be maintained over a wider range.