Audio editing in the time-frequency domain using the Gabor Wavelet Transform
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Visualization, processing and editing of audio, directly on a time-frequency surface, is the scope of this thesis. More precisely the scalogram produced by a Gabor Wavelet transform is used, which is a powerful alternative to traditional techinques where the wave form is the main visual aid and editting is performed by parametric filters. Reconstruction properties, scalogram design and enhancements as well audio manipulation algorithms are investigated for this audio representation.The scalogram is designed to allow a flexible choice of time-frequency ratio, while maintaining high quality reconstruction. For this mean, the Loglet is used, which is observed to be the most suitable filter choice. Re-assignmentare tested, and a novel weighting function using partial derivatives of phase is proposed. An audio interpolation procedure is developed and shown to perform well in listening tests.The feasibility to use the transform coefficients directly for various purposes is investigated. It is concluded that Pitch shifts are hard to describe in the framework while noise thresh holding works well. A downsampling scheme is suggested that saves on operations and memory consumption as well as it speeds up real world implementations significantly. Finally, a Scalogram 'compression' procedure is developed, allowing the caching of an approximate scalogram.
Place, publisher, year, edition, pages
UPTEC F, ISSN 1401-5757 ; F 11 022
Wavelet transform, time-frequency analysis, audio engineering, signal processing, audio restoration, audio interpolation, pitch-shift, time-stretch, loglet, compression, down-sampling, visualization, fourier transform, convolution, filter bank, digital filters, noise reduction, re-assignment, gabor transform, scalogram
IdentifiersURN: urn:nbn:se:uu:diva-153634OAI: oai:DiVA.org:uu-153634DiVA: diva2:417358
Brun, Anders, postdoctoral fellowNyberg, Tomas