An Analysis of Startup and Dynamic Latency in phase vocoder-Based Time-stretching Algorithms

The phase vocoder has become a popular method for timestretching audio (altering its play rate without changing its pitch) in recent years. Despite continuing improvements to the algorithm itself for enhanced audio quality, the latency introduced by the processing is less wellunderstood. Such an understanding is crucial for accurate synchronization in the context of a larger interactive multimedia or computer music system. Our analysis shows that the phase vocoder has an effective startup latency of 2 (Ra −Rs), and a dynamic latency (in response to rate changes) of 2Rs, where Ra and Rs are the input and output hop factors used for time-stretching.

[1]  G.E. Moore,et al.  Cramming More Components Onto Integrated Circuits , 1998, Proceedings of the IEEE.

[2]  Ronen Barzel,et al.  Audio Anecdotes II: Tools, Tips, and Techniques for Digital Audio , 2004 .

[3]  Ken Greenebaum.  Sample Accurate Synchronization Using Pipelines: Put a Sample in and We Know when It Will Come Out , 2007 .

[4]  M.G. Bellanger,et al.  Digital processing of speech signals , 1980, Proceedings of the IEEE.

[5]  J. L. Flanagan,et al.  PHASE VOCODER , 2008 .

[6]  Ken Greenebaum.  Synchronization Demystified: An Introduction to Synchronization Terms and Concepts , 2007 .

[7]  Werner Verhelst,et al.  An overlap-add technique based on waveform similarity (WSOLA) for high quality time-scale modification of speech , 1993, 1993 IEEE International Conference on Acoustics, Speech, and Signal Processing.

[8]  Axel Röbel,et al.  Transient detection and preservation in the phase vocoder , 2003, ICMC.

[9]  Jean Laroche,et al.  Improved phase vocoder time-scale modification of audio , 1999, IEEE Trans. Speech Audio Process..

[10]  Jan Borchers,et al.  DiMaß:: a technique for audio scrubbing and skimming using direct manipulation , 2006, AMCMM '06.

[11]  Jan O. Borchers,et al.  PhaVoRIT: A Phase Vocoder for Real-Time Interactive Time-Stretching , 2006, ICMC.

[12]  Jan O. Borchers,et al.  Toward a Framework for Interactive Systems to Conduct Digital Audio and Video Streams , 2006, Computer Music Journal.

[13]  Jean Laroche,et al.  Application of the phase vocoder to pitch-preserving synchronization of an audio stream to an external clock , 1999, Proceedings of the 1999 IEEE Workshop on Applications of Signal Processing to Audio and Acoustics. WASPAA'99 (Cat. No.99TH8452).