Download Reverse Engineering Stereo Music Recordings Pursuing an Informed Two-Stage Approach
A cascade reverse engineering approach is presented which uses an explicit model of the music production chain. The model considers both the mixing and the mastering stages and incorporates a parametric signal model. The approach is further pursued in an informed scenario. This means that the model parameters are attached in the form of auxiliary data to the mastered mix. They are resorted to afterwards in order to undo the mastering and the mixing. The validity of the approach is demonstrated on a stereo mixture.
Download Synthetic Transaural Audio Rendering (STAR): a Perceptive Approach for Sound Spatialization
The principles of Synthetic Transaural Audio Rendering (STAR) were first introduced at DAFx-06. This is a perceptive approach for sound spatialization, whereas state-of-the-art methods are rather physical. With our STAR method, we focus neither on the wave field (such as HOA) nor on the sound wave (such as VBAP), but rather on the acoustic paths traveled by the sound to the listener ears. The STAR method consists in canceling the cross-talk signals between two loudspeakers and the ears of the listener (in a transaural way), with acoustic paths not measured but computed by some model (thus synthetic). Our model is based on perceptive cues, used by the human auditory system for sound localization. The aim is to give the listener the sensation of the position of each source, and not to reconstruct the corresponding acoustic wave or field. This should work with various loudspeaker configurations, with a large sweet spot, since the model is neither specialized for a specific configuration nor individualized for a specific listener. Experimental tests have been conducted in 2015 and 2019 with different rooms and audiences, for still, moving, and polyphonic musical sounds. It turns out that the proposed method is competitive with the state-of-the-art ones. However, this is a work in progress and further work is needed to improve the quality.
Download First-Order Ambisonic Coding with PCA Matrixing and Quaternion-Based Interpolation
We present a spatial audio coding method which can extend existing speech/audio codecs, such as EVS or Opus, to represent first-order ambisonic (FOA) signals at low bit rates. The proposed method is based on principal component analysis (PCA) to decorrelate ambisonic components prior to multi-mono coding. The PCA rotation matrices are quantized in the generalized Euler angle domain; they are interpolated in quaternion domain to avoid discontinuities between successive signal blocks. We also describe an adaptive bit allocation algorithm for an optimized multi-mono coding of principal components. A subjective evaluation using the MUSHRA methodology is presented to compare the performance of the proposed method with naive multi-mono coding using a fixed bit allocation. Results show significant quality improvements at bit rates in the range of 52.8 kbit/s (4 × 13.2) to 97.6 kbit/s (4 × 24.4) using the EVS codec.
Download Interaural Cues Cartography: Localization Cues Repartition for Three Spatialization Methods
The Synthetic Transaural Audio Rendering (STAR) method, first introduced at DAFx-06 then enhanced at DAFx-19, is a perceptive approach for sound spatialization aiming at reproducing the acoustic cues at the ears of the listener, using loudspeakers. To validate the method, several comparisons with state-of-the-art spatialization methods (VBAP and HOA) were conducted. Previously, quality comparisons with human subjects have been made, providing meaningful subjective results in real conditions. In this article an objective comparison is proposed, using acoustic cues error maps. The cartography enables us to study the spatialization effect in a 2D space, for a listening position within an audience, and thus not necessarily located at the center. Two approaches are conducted: the first simulates the binaural signals for a virtual KEMAR manikin, in ideal conditions and with a fine resolution; the second records these binaural signals using a real KEMAR manikin, providing real data with reverberation, though with a coarser resolution. In both cases the acoustic cues were derived from the binaural signals (either simulated or measured), and compared to the reference value taken at the center of the octophonic loudspeakers configuration. The obtained error maps display comforting results, our STAR method producing the smallest error for both simulated and experimental conditions.
Download Informed Source Separation for Stereo Unmixing — An Open Source Implementation
Active listening consists in interacting with the music playing and has numerous potential applications from pedagogy to gaming, through creation. In the context of music industry, using existing musical recordings (e.g. studio stems), it could be possible for the listener to generate new versions of a given musical piece (i.e. artistic mix). But imagine one could do this from the original mix itself. In a previous research project, we proposed a coder / decoder scheme for what we called informed source separation: The coder determines the information necessary to recover the tracks and embeds it inaudibly (using watermarking) in the mix. The decoder enhances the source separation with this information. We proposed and patented several methods, using various types of embedded information and separation techniques, hoping that the music industry was ready to give the listener this freedom of active listening. Fortunately, there are numerous other applications possible, such as the manipulation of musical archives, for example in the context of ethnomusicology. But the patents remain for many years, which is problematic. In this article, we present an open-source implementation of a patent-free algorithm to address the mixing and unmixing audio problem for any type of music.