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Extensions to Probabilistic Linear Discriminant Analysis for Speaker Recognition
Plchot, Oldřich ; Fousek, Petr (oponent) ; McCree,, Alan (oponent) ; Burget, Lukáš (vedoucí práce)
This thesis deals with probabilistic models for automatic speaker verification. In particular, the Probabilistic Linear Discriminant Analysis (PLDA) model, which models i--vector representation of speech utterances, is analyzed in detail. The thesis proposes extensions to the standard state-of-the-art PLDA model. The newly proposed Full Posterior Distribution PLDA models the uncertainty associated with the i--vector generation process. A new discriminative approach to training the speaker verification system based on the~PLDA model is also proposed. When comparing the original PLDA with the model extended by considering the i--vector uncertainty, results obtained with the extended model show up to 20% relative improvement on tests with short segments of speech. As the test segments get longer (more than one minute), the performance gain of the extended model is lower, but it is never worse than the baseline. Training data are, however, usually available in the form of segments which are sufficiently long and therefore, in such cases, there is no gain from using the extended model for training. Instead, the training can be performed with the original PLDA model and the extended model can be used if the task is to test on the short segments. The discriminative classifier is based on classifying pairs of i--vectors into two classes representing target and non-target trials. The functional form for obtaining the score for every i--vector pair is derived from the PLDA model and training is based on the logistic regression minimizing the cross-entropy error function between the correct labeling of all trials and the probabilistic labeling proposed by the system. The results obtained with discriminatively trained system are similar to those obtained with generative baseline, but the discriminative approach shows the ability to output better calibrated scores. This property leads to a better actual verification performance on an unseen evaluation set, which is an important feature for real use scenarios.
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Unsupervised Evaluation of Speaker Recognition System
Odehnal, Ondřej ; Plchot, Oldřich (oponent) ; Matějka, Pavel (vedoucí práce)
The context of this thesis is the state-of-the-art system for speaker identification (SID) based on the deep nerual network with x-vector embeddings. This thesis aims to propose and experimentally assess several techniques for evaluating the SID system using unlabelled datasets. For this purpose, discriminative embedding is created for every recording in the dataset. These embeddings are used to cluster the recordings and thus create pseudo-labels corresponding to different clusters. The SID system evaluation is based on equal error rate (EER), which uses these pseudo-labels. We proposed several unsupervised learning algorithms to achieve this; K-means, Gaussian mixture models (GMM), and agglomerative hierarchical clustering (AHC). After thorough testing, the K-means model with the Silhouette value showed the best results. This method achieved an estimate of 5.72 % EER with the reference EER equal to 5.15 % on SITW dev-core-core. Similar results were observed on the SITW eval-core-core, where the estimated EER is equal to 5.86 % and the reference 5.08 %. The difference between estimated and reference EER is 0.57 % for the dev-core-core and 0.78 % for the eval-core-core. Another series of experiments were conducted on NIST SRE16 and VoxCeleb1 to verify robustness of the proposed method. Generally, the developed testing process had an estimated error of around 1 % in all test databases, an excellent result for an unsupervised learning technique.
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Hledání nových cest v rozpoznávání řečníka založeného na neuronových sítích
Sova, Damián ; Matějka, Pavel (oponent) ; Glembek, Ondřej (vedoucí práce)
Keďže zadanie tejto práce je veľmi široké, tak sa bolo treba sústrediť len na určitú sféru. Nakoniec, cieľom tejto práce je aplikovať optimalizačnú metódu Stochastického Spriemerovania Váh do tréningového procesu Hlbokej Neurónovej Siete. Po predstavení potrebných teoretických vedomostí v prvej časti práce, nasleduje druhá časť s priebehmi jednotlivých experimentov. V teoretickej časti je dôraz kladený hlavne na objasnenie celého životného cyklu trénovacieho a vyhodnocovacieho procesu, vrátane popisu jednotlivých komponentov. Praktická časť poskytuje podrobný pohľad na každý experiment, ktorých cieľom je demonštrovať dosiahnuteľnosť zvýšenia výkonnosti systému rozpoznávania rečníka. Celkové zlepšenie výkonu sa podarilo dosiahnuť postupným aplikovaním rôznych tréningových konfigurácií, v ktorých sa zohľadňujú skúsenosti z predchádzajúcich experimentov. Kľúčovou zložkou úspešného Stochastického Spriemerovania Váh v experimentoch bola dostatočne vysoká konštantná hodnota Miery Učenia s aplikovaným postupným prechodom alebo Cyklický priebeh Miery Učenia.
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Robustní rozpoznávání mluvčího pomocí neuronových sítí
Profant, Ján ; Rohdin, Johan Andréas (oponent) ; Matějka, Pavel (vedoucí práce)
Tématem této práce je analýza nejmodernějších systémů pro rozpoznávání řečníka za použití neurónových sítí (nazývaných x-vektory) v rozličných podmínkách, jako jsou širokopásmové a úzkopásmové data, který je robustní vůči neviděnému jazyku, specifickému hluku nebo telefonnimu kodeku. Automatický systém mapuje zvukovou nahrávku variabilní délky do fixně dlouhého vektoru, který je následně využit jako reprezentace řečníka. V této práci jsme porovnali systémy založené na neurónových sítich s výsledkem VUT týmu v Speakers in the Wild Speaker Recognition Challenge (SITW), který využíval donedávna velmi populární statistický model - i-vektory. Pozorovali jsme, že s nedávno publikovanými x-vektory dosahujeme 4.38 krát nižší Equal Error Rate pro SITW core-core evaluační sadu v porovnání s výsledkem z roku 2016 od VUT v SITW soutěži. Kromě toho jsme ukázali, že diarizace v nahrávkach s více mluvčími významně snižuje chybovost systému pro SITW core-multi evaluační data, ale podobný trend jsme neviděli pro dataset NIST SRE 2018 VAST.
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Optimization of Gaussian Mixture Subspace Models and Related Scoring Algorithms in Speaker Verification
Glembek, Ondřej ; Brummer, Niko (oponent) ; Campbell,, William (oponent) ; Burget, Lukáš (vedoucí práce)
This thesis deals with Gaussian Mixture Subspace Modeling in automatic speaker recognition. The thesis consists of three parts. In the first part, Joint Factor Analysis (JFA) scoring methods are studied. The methods differ mainly in how they deal with the channel of the tested utterance. The general JFA likelihood function is investigated and the methods are compared both in terms of accuracy and speed. It was found that linear approximation of the log-likelihood function gives comparable results to the full log-likelihood evaluation while simplyfing the formula and dramatically reducing the computation speed. In the second part, i-vector extraction is studied and two simplification methods are proposed. The motivation for this part was to allow for using the state-of-the-art technique on small scale devices and to setup a simple discriminative-training system. It is shown that, for long utterances, while sacrificing the accuracy, we can get very fast and compact i-vector systems. On a short-utterance(5-second) task, the results of the simplified systems are comparable to the full i-vector extraction. The third part deals with discriminative training in automatic speaker recognition. Previous work in the field is summarized and---based on the knowledge from the earlier chapters of this work---discriminative training of the i-vector extractor parameters is proposed. It is shown that discriminative re-training of the i-vector extractor can improve the system if the initial estimation is computed using the generative approach.
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Rozpoznávání mluvčího
Kašpar, Ladislav ; Atassi, Hicham (oponent) ; Sysel, Petr (vedoucí práce)
Ve své bakalářské práci se věnuji problému rozpoznávání mluvčího. Tato práce obsahuje základní teorie k tomuto tématu. Teorie je zaměřena na výpočet parametrů pro rozpoznávání mluvčího a na popis postupu při rozpoznávání mluvčího. Jako hlavní parametry v programu na rozpoznávání mluvčího napsaného v jazyce Matlab využívám kmitočty formantů, kepstrální koeficienty a segmentaci signálu.
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Personal Voice Activity Detection
Sedláček, Šimon ; Landini, Federico Nicolás (oponent) ; Švec, Ján (vedoucí práce)
This work aims to implement, test, and evaluate a speaker-conditioned Voice Activity Detection (VAD) method called Personal VAD. The method builds upon an LSTM-based approach to VAD and its purpose is to introduce a system that can reliably detect speech of a target speaker, while retaining the typical characteristics of a VAD system, mainly in terms of small model size, low latency, and low necessary computational resources. The system is trained to distinguish between three classes: non-speech, target speaker speech, and non-target speaker speech. For this purpose, the method utilizes speaker embeddings as a part of the input feature vector to represent the target speaker. Some of the more heavyweight personal VAD variants also make use of speaker verification scores issued to each frame based on the target embedding, resulting in a more robust system. In addition to the one scoring method presented in the original article, two other scoring approaches are introduced, both outperforming the baseline method and improving the performance even for acoustically challenging conditions.
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Speaker Recognition in the VoIP Environment
Remeš, Jan ; Pešán, Jan (oponent) ; Plchot, Oldřich (vedoucí práce)
This work describes using speaker recognition systems in the VoIP environment, system performance and approaches to improving it. System architecture, evaluation metrics and VoIP technology key components from the view of speaker recognition are described. VoIP environment simulation is described. Speaker recognition system's performance is evaluated on data sets from various kinds of VoIP environments and the results are demonstrated. System adaptation and calibration is performed and their benefits are discussed.
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Speaker Recognition Based on Long Temporal Context
Fér, Radek ; Matějka, Pavel (oponent) ; Černocký, Jan (vedoucí práce)
This work deals with temporal features for automated speaker recognition. We give overview of currently known temporal feature extraction methods and afterwards, we propose and preliminarily evaluate a general phoneme-level temporal feature extraction scheme based on factor analysis i-vector paradigm. Much effort has been made to reasonably represent temporal context and make speaker recognition systems more robust, namely speech prosody modeling. Our approach does not explicitly model any temporal parameters of speech, rather it uses the occurrence of neighboring frames as a source of temporal information. We test and analyze this method on standard evaluation database NIST SRE 2008. The results indicate, however, that for speaker recognition, no useful gain can be obtained using this technique. We describe and discuss this discovery at the end.
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Ukázkový systém na rozpoznávání mluvčích
Šústek, Martin ; Šebesta, Vladimír (oponent) ; Sigmund, Milan (vedoucí práce)
Ve své diplomové práci se věnuje problému rozpoznávání mluvčích. V textu je popsána základní teorie k tomuto tématu, návrh a realizace systému pro rozpoznávání tří mluvčích. V teorii se zabývám výpočtem parametrů pro rozpoznávání mluvčích. Program pro rozpoznávání je vytvořen v Matlabu jako samostatná aplikace. Program je napsán dvojjazyčně česky a anglicky. Pro správnou funkci systému potřebujeme mít mikrofon a zvukovou kartu v počítači s operačním systém Windows.
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