Download Polyphonic Transcription Using Piano Modeling for Spectral Pattern Recognition
Polyphonic transcription needs a correct identification of notes and chords. We have centered the efforts in piano chords identification. Pattern recognition using spectral patterns has been used as the identification method. The spectrum of the signal is compared with a set of spectra (patterns). The patterns are generated by a piano model that takes into account acoustic parameters and typical manufacturer criteria, that are adjusted by training the model with a few notes. The algorithm identifies notes and, iteratively, chords. Chords identification requires spectral substraction that is performed using masks. The analyzing algorithm used for training, avoids false partials detection due to nonlinear components and takes into account inharmonicity for spectrum segmentation. The method has been tested with live piano sounds recorded from two different grand pianos. Successful identification of up to four-notes chords has been carried out.
Download Multichannel audio decorrelation for coding
Within digital audio codification, the processing of multichannel signals has become one of the main fields of research. Current work on the subject look for effective ways to exploit the existing redundancy between the different channels in order to reduce the codification binary rate. This work studies the Karhunen-Loeve Transform (KLT) as a method of decorrelating multi-channel signals prior to coding. Results on codification via AAC are reported.
Download Piano Transcription Using Pattern Recognition: Aspects on Parameter Extraction
A method for chord recognition for piano transcription has been previously presented by the authors. The method presents some limitations due to errors in parameter extraction carried out during the training process. Parameter extraction of piano notes is not as straightforward as sometimes can be thought. Spectral components detection is necessary but not enough to obtain accurately some note parameters. The inharmonicity coefficient B is one of the parameters that are difficult to evaluate. The obtained value of B is different for every partial used to calculate it, and sometimes, these differences are high. Tuning with respect to tempered scale is another important note parameter. The problems arise when we try to measure the tuning of a note belonging to octaves 0 or 1, because the fundamental is radiated by the soundboard with a very low level and, therefore, it is not captured by the recording microphone and cannot be measured. A method to avoid these drawbacks is presented in this paper, including an explanation of the basis.
Download Source Separation for WFS Acoustic Opening Applications
This paper proposes a new scheme to reduce coding bit rate in array based multichannel audio applications like the acoustic opening, which can be used for modern teleconference systems. The combination of beamforming techniques for source separation and wave field synthesis allows a significant coding bit rate reduction. To evaluate the quality of this new scheme, both objective and subjective tests have been carried out. The objective measurement system is based on the Perceptual Audio Quality Measure of the binaural signal that the listener would perceive in a real environment.