Speaker Recognition Systems - ICSIfractor/fall2011/pres1.pdf · • Speaker adaptive cohort selection for Tnorm in text-independent speaker verification – Sturim, Reynolds (2005)

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The 2004 MIT Lincoln Laboratory Speaker Recognition System

D.A.Reynolds, W. Campbell, T. Gleason, C. Quillen, D. Sturim, P. Torres-Carrasquillo, A. Adami (ICASSP 2005)

CS298 Seminar

Shaunak Chatterjee

09-23-2011 1

Actually …

• Robust text-independent speaker identification using Gaussian mixture speaker models – Reynolds, Rose (1995)

• Speaker verification using adapted Gaussian mixture models – Reynolds, Quatieri, Bunn (2000)

• Speaker recognition based on idiolectal differences between speakers – Doddington (2001)

• Generalized linear discriminant sequence kernels for speaker recognition – Campbell (2002)

• Modeling prosodic dynamics for speaker recognition – Adami, Mihaescu, Reynolds, Godfrey (2003)

• Speaker adaptive cohort selection for Tnorm in text-independent speaker verification – Sturim, Reynolds (2005)

• The 2004 MIT Lincoln Laboratory Speaker Recognition System – Reynolds et al (2005)

• The MIT Lincoln Laboratory 2008 Speaker Recognition System – Sturim, Campbell, Karam, Reynolds, Richardson (2009)

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Douglas A. Reynolds

• PhD (Georgia Tech, 1992)

• Currently Senior Member of Technical Staff at MIT Lincoln Lab

• Most cited author in speaker recognition (by far?)

• Contributed several key ideas currently used in robust speaker recognition systems

• MIT Lincoln Lab has won numerous awards at the NIST SRE over the years

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What can we learn from speech?

Slide courtesy: Reynolds, Heck 4

Speaker Recognition

Identification

• No identity claim is made

• Classification

Verification

• Identity claim is made

• Binary decision

• Open-set vs closed-set • Text-dependent vs text-independent

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Applications

• (Telephonic) Transaction Authentication

• Access Control

– Physical facilities

– Computer and data networks

• Parole Monitoring

• Information Retrieval

– Audio indexing in call centers

• Forensics

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Components of a speaker recognition system


Universal Background Model

Background’s “Voiceprint”

Phases of speaker verification


Feature Extraction

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Feature Extraction

• Pre-processing

– Bandlimiting

– Silence, noise removal

– Channel bias removal (RASTA et al)

• Feature computation

– MFCC computed every 10ms over a 20ms window

– F0 and energy features

– Phonetic features

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Speaker models




Gaussian mixture models (GMMs)

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• Trained using EM • Often converges within 5 iterations • Wide range of choices to constrain

parameters

Why GMMs? - I Histogram of one cepstral coefficient for a 25-second speech sequence Unimodal distribution Gaussian mixture model Vector Quantization (VQ)

[Reynolds 95] 13

Why GMMs? - II

Each component of the GMM corresponds to a speaker-dependent vocal tract configuration

[Reynolds 95] Image: wikipedia 14

Text-dependent vs text-independent

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Slide courtesy: Reynolds, Heck

Speaker models




Hypothesis testing

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2004 MIT Lincoln Lab Speaker Recognition System (MITLL)

• Seven core systems – Spectral based

• GMM-UBM

• (Spectral) SVM

– Prosodic based • Pitch and Energy GMM

• Slope and duration GMM

– Phonetic based • Phone N-grams

• Phone SVM

– Idiolectal based

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• GMM-UBM

• (Spectral) SVM




• Phone SVM


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Feature Extraction – GMM-UBM

• 19-dimensional MFCC every 10ms using a 20ms window

• Bandlimiting: 300-3138Hz

• RASTA filtering

– To reduce channel bias effects

• Δ-cepstral coefficients computed for ±2 frames

• Silence removal, feature mapping, normalization

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UBM training

• Gender-independent 2048 mixture UBM trained from Switchboard and OGI National Cellular Database Corpora – MIXER corpus (the test data) was not used

• Target models (for individual speakers) are derived by Bayesian adaptation of the UBM parameters and training data from MIXER – “compensating” for UBM

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• GMM-UBM

• (Spectral) SVM




• Phone SVM


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Support Vector Machines (SVM)

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SVM - II

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SVM - III

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Spectral SVM (for speech)

• Campbell (2002) showed that good performance in speaker recognition tasks could be achieved using sequence kernels

• Sequence kernel: provides a numerical comparison of speech utterances as entire sequences

• Campbell introduced a novel sequence kernel derived from generalized linear discriminants

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SVM setup in MITLL

• Same front-end processing as before

• Background (or the other class) for every speaker consisted of a set of speakers taken from Switchboard

– Current speaker under training had target of +1 and every other speaker had target of -1

• SVM training was performed using the GLDS kernel

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• GMM-UBM

• (Spectral) SVM




• Phone SVM


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Prosodic based systems

• Prosody: the rhythm, stress and intonation of speech

• Spectral approaches focus on capturing short-term information

• Prosodic systems can model long-term information

• Two systems in 2004 MITLL SRS – Distribution based pitch/energy classifier

– Pitch/energy sequence modeling system

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Pitch and Energy GMM

• Very similar to GMM-UBM

– Main difference: feature set

• Log F0 and log energy estimated every 10ms using RAPT – Robust Algorithm for Pitch Tracking (Talkin 1995)

• Δ features (over 50ms window) appended

• Silence and noisy region removal

• UBM: 512 components (Switchboard)

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What is F0?

• Fundamental frequency of a human voice

– Between 85-180 in males

– 165-255 in females

– Range is below most band

limits

– Higher harmonics are

transmitted

– F0 is not static

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Slope and duration n-gram - I

• The dynamics of F0 and energy also convey information about speaker identity

• Dynamics of both trajectories jointly represent certain prosodic gestures characteristic of a speaker (Adami et al, 2003)

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Slope and duration n-gram - II

• F0 and energy trajectories converted into a sequence of tokens

– Each token reflects a joint state of the trajectories (rising or falling)

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• GMM-UBM

• (Spectral) SVM




• Phone SVM


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Phonetic based system - I

• Gender independent phone recognition

• Phone recognizers trained on phonetically marked speech from OGI multi-language corpus

• Output token streams were processed to produce a sequence of token symbols

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Phonetic based system – II

• Two systems

– Standard n-gram modeling

• Bi-gram model estimated for each speaker (for each phone/language)

• UBM from Switchboard

• 6 scores fused

– Phone SVM

• Very similar to Spectral SVM

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• GMM-UBM

• (Spectral) SVM




• Phone SVM


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Idiolectal differences

• Only look at content!

• It is possible to determine authorship of papers/literary works by looking at them

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Idiolectal differences

• Speech content is conventionally less constrained and therefore more distinctive

• Unfortunately, a lot of data is needed for reasonable accuracy

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MITLL idiolectal based system

• Only considered bigrams

– Trigrams and higher did not improve performance

• Switchboard data used to create UBM

• BBN Byblos 3.0 used for speech-to-text conversion

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System fusion

• Perceptron classifier

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Performance measure


DET – different scenarios

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Slide courtesy: Reynolds, Heck

Results - I

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Results - II

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No gain from higher-level information

• All development data from English – Could have led to a bias in the UBMs

• SRE04 dataset had tons of channel mismatch – More difficult task, potentially masks gains

• Both are essentially mismatches between training and test distributions/data

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Results - III

• All Pool: all languages • Common pool: English

only

• Clear indication of cross-lingual degradation

• N-gram system reduces error significantly

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Conclusions

• 2004 MITLL system attempted to exploit other levels of information (prosodic, phonetic, idiolectal) to better characterize and recognize a speaker

• 7 core systems • Generative, discriminative and discrete classifiers • Results on the “challenging” MIXER corpus

(SRE04) • Previous success in system fusion needs to be

tailored better for cross-lingual environments

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2008 MITLL Speaker Recognition system (Interspeech 2009)

• Two main themes

– Variational nuisance modeling to allow for better compensation for channel variation

– Fuse systems targeting different linguistic tiers of information (high and low)

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QUESTIONS?

Thanks for the attention!

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Documents

Speaker Recognition Systems - ICSIfractor/fall2011/pres1.pdf · • Speaker adaptive cohort selection for Tnorm in text-independent speaker verification – Sturim, Reynolds (2005)