Section: New Results
Source Localization and Separation
Source separation, sparse representations, probabilistic model, source localization
Acoustic source localization is, in general, the problem of determining the spatial coordinates of one or several sound sources based on microphone recordings. This problem arises in many different fields (speech and sound enhancement, speech recognition, acoustic tomography, robotics, aeroacoustics...) and its resolution, beyond an interest in itself, can also be the key preamble to efficient source separation, which is the task of retrieving the source signals underlying a multichannel mixture signal. Over the last years, we proposed a general probabilistic framework for the joint exploitation of spatial and spectral cues , hereafter summarized as the “local Gaussian modeling”, and we showed how it could be used to quickly design new models adapted to the data at hand and estimate its parameters via the EM algorithm. This model became the basis of a large number of works in the field, including our own. This accumulated progress lead, in 2015, to two main achievements: a new version of the Flexible Audio Source Separation Toolbox, fully reimplemented, was released  and we published an overview paper on recent and going research along the path of guided separation in a special issue of IEEE Signal Processing Magazine .
From there, our recent work divided into several tracks: maturity work on the concrete use of these tools and principles in real-world scenarios, in particular within the INVATE project and the collaboration with the startup 5th dimension (see Sections 8.1.2, 8.1.4), on the one hand; on the other hand, an emerging track on audio scene analysis with machine learning, evolved beyond the “localization and separation” paradigm, and is the subject of a more recent axis of research presented in Section 7.5.
Towards Real-world Localization and Separation
Participants : Nancy Bertin, Frédéric Bimbot, Rémi Gribonval, Ewen Camberlein, Romain Lebarbenchon, Mohammed Hafsati.
Main collaborations: Emmanuel Vincent (MULTISPEECH Inria project-team, Nancy)
Based on the team's accumulated expertise and tools for localization and separation using the local Gaussian model, two real-world applications were addressed in the past year, which in turn gave rise to new research tracks.
First, our work within the voiceHome project (2015-2017), an OSEO-FUI industrial collaboration (With partners: onMobile, Delta Dore, eSoftThings, Orange, Technicolor, LOUSTIC, Inria Nancy.) aiming at developing natural language dialog in home applications, such as control of domotic and multimedia devices, in realistic and challenging situations (very noisy and reverberant environments, distant microphones) found its conclusion with the publication of a journal paper in a special issue of Speech Communication .
Accomplished progress and levers of improvements identified thanks to this project resulted in the granting of an Inria ADT (Action de Développement Technologique). This new development phase of the FASST software started in September 2017 and was achieved this year by the release of the third version of the toolbox, with significant progress towards efficient initialization, low latency and reduction of the computational burden.
In addition, evolutions of the MBSSLocate software initiated during this project led to a successful participation in the IEEE-AASP Challenge on Acoustic Source Localization and Tracking (LOCATA) , and served as a baseline for the publication of the for the IEEE Signal Processing Cup 2019 . The SP Cup was also fueled by the publicly available DREGON dataset 5 recorded in PANAMA, including noiseless speech and on-flight ego-noise recordings, devoted to source localization from a drone .
Finally, these progress also led to a new industrial transfer with the start-up 5th dimension (see Section 8.1.4). During this collaboration aiming at equipping a pair of glasses with an array of microphones and “smart” speech enhancement functionalities, we particularly investigated the impact of obstacles between microphones in the localization and separation performance, the selection of the best subset of microphones in the array for side speakers hidden by the head shadow, and the importance of speaker enrolment (learning spectral dictionaries of target users voices) in this use case.
Separation for Remixing Applications
Participants : Nancy Bertin, Rémi Gribonval, Mohammed Hafsati.
Main collaborations: Nicolas Epain (IRT bcom, Rennes)
Second, through the Ph.D. of Mohammed Hafsati (in collaboration with the IRT bcom with the INVATE project, see Section 8.1.2) started in November 2016, we investigated a new application of source separation to sound re-spatialization from Higher Order Ambisonics (HOA) signals , in the context of free navigation in 3D audiovisual contents. We studied the applicability conditions of the FASST framework to HOA signals and benchmarked localization and separation methods in this domain. Simulation results showed that separating sources in the HOA domain results in a 5 to 15 dB increase in signal-to-distortion ratio, compared to the microphone domain. These results were accepted for publication in the DAFx international conference . We continued extending our methods following two tracks: hybrid acquisition scenarios, where the separation of HOA signals can be informed by complementary close-up microphonic signals, and the replacement of spectrogram NMF by neural networks for a better spectral adaptation of the models. Future work will include subjective evaluation of the developed workflows.