Download Realtime system for backing vocal harmonization A system for the synthesis of backing vocals by pitch shifting of a lead vocal signal is presented. The harmonization of the backing vocals is based on the chords which are retrieved from an accompanying instrument. The system operates completely autonomous without the need to provide the key of the performed song. This simplifies the handling of the harmonization effect. The system is designed to have realtime capability to be used as live sound effect.
Download Improved PVSOLA Time Stretching and Pitch Shifting for Polyphonic Audio An advanced phase vocoder technique for high quality audio pitch shifting and time stretching is described. Its main concept is based on the PVSOLA time stretching algorithm which is already known to give good results on monophonic speech. Some enhancements are proposed to add the ability to process polyphonic material at equal quality by distinguishing between sinusoidal and noisy frequency components. Furthermore, the latency is reduced to get closer to a real time implementation. The new algorithm is embedded into a flexible pitch shifting and time stretching framework by adding transient detection and resampling. A subjective listening test is used to evaluate the new algorithm and to verify the improvements.
Download The Tonalness Spectrum: Feature-Based Estimation of Tonal Components The tonalness spectrum shows the likelihood of a spectral bin being part of a tonal or non-tonal component. It is a non-binary measure based on a set of established spectral features. An easily extensible framework for the computation, selection, and combination of features is introduced. The results are evaluated and compared in two ways. First with a data set of synthetically generated signals but also with real music signals in the context of a typical MIR application.
Download Polyphonic Pitch Detection by Iterative Analysis of the Autocorrelation Function In this paper, a polyphonic pitch detection approach is presented, which is based on the iterative analysis of the autocorrelation function. The idea of a two-channel front-end with periodicity estimation by using the autocorrelation is inspired by an algorithm from Tolonen and Karjalainen. However, the analysis of the periodicity in the summary autocorrelation function is enhanced with a more advanced iterative peak picking and pruning procedure. The proposed algorithm is compared to other systems in an evaluation with common data sets and yields good results in the range of state of the art systems.
Download Stereo signal separation and upmixing by mid-side decomposition in the frequency-domain An algorithm to estimate the perceived azimuth directions in a stereo signal is derived from a typical signal model. These estimated directions can then be used to separate direct and ambient signal components and to remix the original stereo track. The processing is based on the idea of a bandwise mid-side decomposition in the frequency-domain which allows an intuitive and easy to understand mathematical derivation. An implementation as a stereo to five channel upmix is able to deliver a high quality surround experience at low computational costs and demonstrates the practical applicability of the presented approach.
Download Downmix compatible conversion from mono to stereo in time- and frequency-domain Even in a time of surround and 3D sound, many tracks and recordings are still only available in mono or it is not feasible to record a source with multiple microphones for several reasons. In these cases, a pseudo stereo conversion of mono signals can be a useful preprocessing step and/or an enhancing audio effect. The conversion proposed in this paper is designed to deliver a neutral sounding stereo image by avoiding timbral coloration or reverberation. Additionally, the resulting stereo signal is downmix-compatible and allows to revert to the original mono signal by a simple summation of the left and right channels. Several configuration parameters are shown to control the stereo panorama. The algorithm can be implemented in time-domain or also in the frequency-domain with additional features, like center focusing.
Download Time-Domain Implementation of a Stereo to Surround Sound Upmix Algorithm This paper describes a time-domain algorithm to upmix stereo recordings for an enhanced playback on a surround sound loudspeaker setup. It is mainly the simplified version of a previously published frequency-domain algorithm where the standard shorttime Fourier transform is now replaced by an IIR filter bank. The design of complementary filter blocks and their arrangement in a tree structure to form a filter bank are derived. The arithmetic complexity of the filter bank itself and of the complete upmix algorithm is analysed and compared to the frequency-domain approach. The time-domain upmix is less flexible in its configuration but achieves an audio quality comparable to the frequency-domain implementation at a fraction of its computational cost.
Download LP-BLIT: Bandlimited Impulse Train Synthesis of Lowpass-filtered Waveforms Using bandlimited impulse train (BLIT) synthesis, it is possible to generate waveforms with a configurable number of harmonics with an equal amplitude. In contrast to the sinc-pulse, which is typically used for bandlimiting in BLIT and only allows to set the cutoff frequency, a Hammerich pulse can be tuned by two independent parameters for cutoff frequency and stop band roll-off. Replacing the perfect lowpass sinc-pulse in BLIT with a Hammerich pulse, it is possible to directly synthesise a multitude of signals with an adjustable lowpass spectrum.