Embodiment
The invention will be described further below in conjunction with drawings and Examples: method of the present invention was divided into for three steps.
The first step, Application on Voiceprint Recognition
Speaker Identification is divided into the voice pre-service, feature extraction, and model training is discerned four parts.
1. voice pre-service
The voice pre-service is divided into sample quantization, zero-suppresses and floats, three parts of pre-emphasis and windowing.
A), sample quantization
I. with sharp filter sound signal is carried out filtering, make its nyquist frequency FNBe 4KHZ;
II., audio sample rate F=2F is setN
III. to sound signal Sa(t) sample by the cycle, obtain the amplitude sequence of digital audio and video signals
IV. with pulse code modulation (pcm) s (n) is carried out quantization encoding, the quantization means s ' that obtains amplitude sequence (n).
B), zero-suppress and float
I. calculate the mean value s of the amplitude sequence that quantizes;
II. each amplitude is deducted mean value, obtaining zero-suppressing, to float back mean value be 0 amplitude sequence s " (n).
C), pre-emphasis
I., Z transfer function H (the z)=1-α z of digital filter is set-1In pre emphasis factor α, the value that the desirable ratio of α 1 is slightly little;
II.s " (n) by digital filter, obtain the suitable amplitude sequence s (n) of high, medium and low frequency amplitude of sound signal.
D), windowing
I. frame length N of computing voice frame (32 milliseconds) and the frame amount of moving T (10 milliseconds), satisfy respectively:
Here F is the speech sample rate, and unit is Hz;
II. be that N, the frame amount of moving are T with the frame length, s (n) is divided into a series of speech frame Fm, each audio frame comprises N voice signal sample;
III. calculate the hamming code window function:
IV. to each speech frame FmAdd hamming code window:
2.MFCC extraction:
A), the exponent number p of Mel cepstrum coefficient is set;
B), be fast fourier transform FFT, time-domain signal s (n) is become frequency domain signal X (k).
C), calculate Mel territory scale:
D), calculate corresponding frequency domain scale:
E), calculate each Mel territory passage φjOn the logarithm energy spectrum:
Wherein
F), be discrete cosine transform DCT
3.DBN model training
Dynamic bayesian network model (DBN) is similar to HMM, is a generation model, and it only needs a people's speech data just can carry out modeling to it, finishes identifying.
The purpose of training is in order to make under given speech data, and the parameter of model can better be described the distribution situation of voice in feature space.Here DBN training mainly lays particular emphasis on the training to model parameter, does not learn at network topology.
A) if likelihood score does not have convergence, and iterations changes B less than preset times) step; Otherwise, change E).
Here convergent definition is:
The PreLogLik here is meant the likelihood score of back iteration, and CurLogLik is meant the likelihood score of current iteration, and they all are by step C) in forward-backward algorithm traversal obtain.θ is the threshold values of presetting.Default maximum iteration time MAXITER can set arbitrarily.The judgement in this step is to make iteration be unlikely to unconfined to carry out.
B), the ASSOCIATE STATISTICS value of each node empties.
Will empty statistical value before forward-backward algorithm traversal, said here statistical value is meant CPD (conditional probability distribution) to node needed data when learning.
C), pooled observations, carry out forward-backward algorithm traversal, the output likelihood score.
Network is carried out the forward-backward algorithm traversal, make observed reading can make other nodes in the network also can obtain upgrading to the renewal of some node, satisfy locally coherence and global coherency condition, this step has realized in abutting connection with algorithm, and the frame inner structure has been carried out the probability diffusion with COLLECT-EVIDENCE (collecting evidence) and DISTRIBUTE-EVIDENCE (issue evidence).This traversal will be exported the Log likelihood score, at A in step) in will be used to.Used probability output also obtains by this traversal in the identification.
D), according to observed reading, calculate the ASSOCIATE STATISTICS value, upgrade the probability distribution of interdependent node, change A).
According to observed reading, calculate the ASSOCIATE STATISTICS value, the probability distribution of new node more, this is determined by the EM learning algorithm.
E), preserve model.
4. identification
After the user speech input,, obtain a characteristic vector sequence C through feature extraction.Press Bayes rule,, meet model M giving under the given data CiLikelihood score be,
Because without any the knowledge of priori, so we think to all models P (Mi) be identical, i.e. P (Mi)=1/N, i=1,2 ..., N, and concerning all speakers, P (C) is a unconditional probability, also is identical, that is:
P(Mi|C)∝P(C|Mi)
We are converted into the posterior probability of asking model and ask the prior probability of model to data.So, speaker's identification test is exactly to calculate following formula,
Second step: recognition of face
2 dimension face identification systems mainly comprise image pre-service, feature extraction and three parts of sorter classification.
1. image pre-service
The pretreated general objects of image is to adjust the difference of original image on illumination and geometry, obtains normalized new images.Pre-service comprises the alignment and the convergent-divergent of image.
2.PCA feature extraction
By the pivot conversion, with a low n-dimensional subspace n (pivot subspace) facial image is described, try hard to when rejecting the classification interference components, remain with the discriminant information that is beneficial to classification.
With the standard picture after pretreated as training sample set, and with the covariance matrix of this sample set generation matrix as the pivot conversion:
X whereiniBe the image vector of i training sample, μ is the average image vector of training sample set, and M is the sum of training sample.If the image size is K * L, then the matrix ∑ has KL * KL dimension.When image is very big, directly calculating the eigenwert and the proper vector that produce matrix will have certain difficulty.As sample number M during less than KL * KL, available svd theorem (SVD) is converted to the calculating of M dimension matrix.
With the eigenwert λ that sorts from big to small0〉=λ1〉=... λR-1, and establish the vectorial u of being of their characteristics of correspondenceiLike this, each width of cloth facial image can project to by u0, u1..., uM-1In the subspace of opening.Obtained M proper vector altogether, chosen preceding k maximum proper vector, made:
Wherein α is called the energy ratio, accounts for the ratio of whole energy for the energy of sample set on preceding k axle.
3. sorter classification
With the arest neighbors sorting technique as component classifier.What distance metric used is the Euclidean distance formula.
The 3rd step: based on the Multiple Classifier Fusion of score difference weighting
Multiple Classifier Fusion algorithm based on the weighting of score difference is divided into the sorter formalized description, trains and discern three parts.
1. sorter formalized description
A), sorter is described: establish D={D1, D2..., DLRepresent a group component sorter;
B), classification is described: establish Ω={ ω1..., ωc) represent a category not identify, promptly all possible classification results
D), output: length is the vectorial D of c
i(x)=[d
I, 1(x), d
I, 2(x) ..., d
I, c(x)]
T, d wherein
I, j(x) represent D
iBelong to for x
The support .d of this guess
I, j(x) normalized to [0,1] interval interior component classifier output, and
E), the output of all sorters can be synthesized a DP (Decision Profile) matrix:
In this matrix, the i row element is represented component classifier D
iOutput D
i(x); The j column element represents each component classifier right
Support.
2. training
A), training sample: the training set X={x that N element arranged1, x2..., xN}
B), sorter is to the recognition result of sample:
S whereinJ, iBe sorter DiTo sample elements xjThe class that is identified, and if only if
sj,i=Di(xj)
Here j=1 ..., N is the number of element in the training set; I=1 ... L is that the number .C of sorter is the number of classification, is number to be identified herein.
C), original affiliated classification: the L (X) of sample=[k
1 ..., k
N]
T,
D), the score difference SD of i sorteri(X) be:
SDi(X) be under separation vessel is differentiated error situation, import this moment data former under the classification of the input data supposed of classification and sorter s when inconsistentJ, i≠ kj, sorter is to the difference of the support of above-mentioned two classifications.D whereinI, j(x) be element in DP (x) matrix.
E), sorter is based on the weights of score difference:
3. judgement
According to weights, recomputate under the multi-modal state support of each classification:
D(x)=[d1(x),d2(x),...,dc(x)]T
A plurality of sorters are ω to the classification results of test vector xsAnd if only if
Experimental result
Native system is tested on a multi-modal speech database that comprises 54 user's vocal prints and voice messaging.This database has been gathered the people's face and the voiceprint of 54 students of Zhejiang University (37 schoolboys, 17 schoolgirls).The collecting work of entire database carries out in the environment of low noise bright and clear.In the phonological component, everyone is required to saypersonal information 3 times; The mandarin numeric string, dialect numeric string, english digit string, mandarin word string, each 10 of picture talks, one section of short essay.The voice document form is the wav/nist form, and all standard becomes the 8000Hz sampling rate, the 16bit data.Experiment adopts short essay and personal information as training, and all the other 50 voice are as test.In the facial image part, everyone respectively produces the front and people from side face shines totally 4, and wherein positive according to two, the side is according to two.Experiment employing wherein positive a photograph is trained, and another is tested.
We use the single mode Application on Voiceprint Recognition simultaneously on this storehouse, single mode recognition of face and addition, weighting, ballot method and carried out same experiment based on this several frequently seen decision-making level's blending algorithm of method of behavior knowledge space, be used for and native system (SDWS is based on the blending algorithm of score difference weighting) compares.Wherein Application on Voiceprint Recognition is based on people's phonetic feature, and recognition of face is based on people's face feature.Blending algorithm combines these two kinds of features, and addition and ballot are owned by France in the fixing fusion method of parameter; Weighted sum belongs to the blending algorithm that needs parameter training based on the method for behavior knowledge space.
Single mode vocal print method for distinguishing speek person is based on the first step of this explanation, voice are carried out pre-service after, it is extracted the Mel cepstrum feature, utilize dynamic Bayesian model to speaker's modeling.Dynamically the topology of Bayesian model adopts structure as shown in Figure 2, wherein qij, i=1,2,3, j=1,2 ... T represents latent node variable, and each node hypothesis has two discrete values, oij, i=1,2,3, j=1,2 ... T is an observer nodes, corresponding to observation vector, has the father node q of Discrete Distributionij, satisfy Gaussian distribution.Same, tested speech is carried out rightly with the speaker model of building up after the process of extracting through pre-service and Mel cepstrum feature, obtains the pairing artificial identification person that speaks of the highest model of branch.
The single mode recognition of face goes on foot based on second of this explanation, after facial image is manuallyd locate according to eyes, it is extracted the PCA feature, by comparing the Euclidean distance between the PCA feature, gets the pairing artificial identification person that speaks of nearest feature.
For addition, its thought can be by following formulate:
μi(x)=F(d1,i(x),...,dL,i(x)),i=1,...,c
Wherein F has represented add operation (Sum), and final classification results is to make μiThe ω of maximum i correspondencei
Weighting algorithm is to grow up on the basis of addition, embodies difference good and bad between each sorter by weight.Here adopt each sorter etc. error rate as its weight.
The basic thought of ballot method is " the minority is subordinate to the majority ".Wherein, the voter is all component classifiers, and the candidate is all possible classification results.Give its candidate's ballot of supporting by the voter, the candidate that poll is maximum wins.
Method based on the behavior knowledge space is to estimate posterior probability under the situation of knowing the component classifier classification results.It need add up the number that each class sample drops on each unit of behavior knowledge space.When using this method, the sample in the training set is divided into different unit, and these unit are that the various combination by all component classifier classification results defines.When a unknown sample need be carried out the branch time-like, all component classifiers all can be known the combination of classification results, can find corresponding unit thus.Then, according to the sample concrete class in this unit, unknown sample is included into the maximum classification of occurrence number.
We are being different under the voice collection of voice content and languages, and single mode identification and above several blending algorithm are assessed.
Assess for performance, select for use discrimination (IR, Identification Rate) to be used as the evaluation criteria of experimental result Speaker Recognition System.
The computing formula of discrimination IR is:
Experimental result is as follows:
| Fusion method | Discrimination (%) |
| Mandarin | Dialect | English | Vocabulary | Picture talk |
| Application on Voiceprint Recognition | 84.63 | 85.55 | 91.11 | 87.78 | 87.78 |
| Recognition of face | 85.18 |
| Addition | 85.37 | 85.18 | 86.11 | 85.18 | 85 |
| Weighting | 85.37 | 85.18 | 86.67 | 85.18 | 85 |
| SDWS | 97.96 | 97.98 | 98.89 | 99.26 | 98.33 |
| The ballot method | 85.18 | 85.18 | 85.18 | 85.18 | 85.18 |
| Method based on the behavior knowledge space | 89.15 | 89.68 | 92.33 | 90.21 | 88.10 |
Experimental result shows that the biological authentication method of single mode can't reach discrimination preferably, can not satisfy the requirement of security and robustness.
Under the situation of two Multiple Classifier Fusion, the method for addition and weighting tends to make the advantage of two sorters disappear mutually on the contrary because do not consider the score distribution situation of sorter.
The ballot method has only been considered the category label of each sorter output, and does not consider their error rate, and this has wasted the information of training sample to a certain extent.
Though behavior knowledge space method is to tie up the direct statistics that distributes more than a plurality of sorter results of decision, the decision-making that can make up component classifier is to obtain best result.Yet, because the relative training sample quantity of behavior knowledge space is too huge, being easy to occur undisciplined situation, this is because training set can't be huge to each unit is filled into enough density.
This recognizer can be by the analysis to the sorter score, according under the situation of sorter identification error, difference between the score of the model under the score of the model that the sorter of collecting is judged and the sample, with this weight as sorter, by simple and effective method of weighting sorter is merged in decision-making level, make two kinds of sorters have complementary advantages, to improving a lot on the system performance, head and shoulders above other fusion method, improved about 7.8-13.3% than the method for single mode.Thereby improved the recognition performance of Speaker Identification.