bandwidth expansion of narrow band speech using linear prediction
DESCRIPTION
Bandwidth Expansion of Narrow band Speech using Linear Prediction. Bjarke Andersen, Jakob Dyreby, Brian Jensen, Frederik Holmelund Kjærskov, Ole Lodahl Mikkelsen, Peter Drustrup Nielsen, Henrik Zimmermann. Group 742 Institute of Electronic Systems Department of Communications Technology - PowerPoint PPT PresentationTRANSCRIPT
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Bandwidth Expansion of Narrow band Speech using Linear
PredictionBjarke Andersen, Jakob Dyreby, Brian Jensen, Frederik Holmelund
Kjærskov, Ole Lodahl Mikkelsen, Peter Drustrup Nielsen, Henrik Zimmermann
Group 742Institute of Electronic Systems
Department of Communications TechnologyAalborg University, 2004
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Agenda
• Præsentation fra Semcon conference
• Poster præsentation
• Abstract
• Arbejdsmetodik og arbejdsblade
• Envelope
• Excitation
• Artikel
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• Bandwidth of speech is more than 8 kHz
• Limited bandwidth of todays system
• Too expensive to expand current telephone systems.
• Expansion at the receiving end of the telephoneline
Todays Narrow band telephone systems
8[kHz]
0
[dB]
0.3 3.4[kHz]
[dB]
80[kHz]
[dB]
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LPsynthesis
Envelopeextension
LPanalysis
LPestimation
Excitationextension
Narrow bandspeech
Wide bandspeech
Codebook
Envelope Estimation
•Transforms the LPC coefficients into LSF (Line Spectrum Frequency)
•Codebook used for prediction of upper frequencies
LSFtransform
Codebookmapping
Inv. LSFTransform
LPsynthesis
Envelopeextension
LPanalysis
LPestimation
Excitationextension
Narrow bandspeech
Wide bandspeech
Codebook
System overview
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LPsynthesis
Envelopeextension
LPanalysis
LPestimation
Excitationextension
Narrow bandspeech
Wide bandspeech
Codebook
Excitation Estimation
•Modulation moves the frequency
•Pitch detection estimates the fundamental frequency
Modulation
Adding ofpitch
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The result
Telephoneswitch
Telephoneswitch
BandwidthExpansion
Public telephone system At the user
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Poster præsentation
Frederik
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Kommunikative virkemidler• Bygget op omkring IMRaD-modellen• Centralt placerede figurer• Selvforklarende figurer• Kortfattet tekst• Tekst underbygges af figurer
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Abstract
Peter
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AbstractOversigt Titel Introduktion Metoder Resultater Diskussion
• Titel
• IMRaD– Introduktion– Metoder– Resultater– Diskussion
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Abstract Oversigt Titel Introduktion Metoder Resultater Diskussion
• Beskrive rapporten så præcist som muligt
• Skal ikke være for lang
• Skal præsentere ”key words”.
• Bandwidth Expansion of Narrowband Speech using Linear Prediction
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Abstract Oversigt Titel Introduktion Metoder Resultater Diskussion
• Beskrivelse af problemstillingen
• Uddybelse af problem, så læseren ikke er i tvivl om hvad projektet handler om
• Kan bruges som en ”appetitvækker”
• ”...,thus making the speech sound more realistic and pleasant”
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Abstract Oversigt Titel Introduktion Metoder Resultater Diskussion
• Forklaring af brugte metoder
• Forklaring af løsningsforslag
• Inddrag ikke resultater i Metoder
• Signal split into two parts....
• LP coefficient → LSF coefficient
• LSF codebook
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Abstract Oversigt Titel Introduktion Metoder Resultater Diskussion
• Forklaring af testmetode
• Præsentation af relevante resultater, evt. Ikke alle resultater fra projektet.
• ”Spectrograms of the reconstructed wideband signal verified.....”
• ”Convergence measurements ranging.....”• Listening test
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Abstract Oversigt Titel Introduktion Metoder Resultater Diskussion
• Opsummerer de mest relevante resultater
• Diskuterer resultaterne
• Diskuterer fremtidigt arbejde
• ”The algorithm for wideband expansion proved to work...”
• ”However, unwanted artefacts developed in the reconstruction af the wideband signal”
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Arbejdsmetodik og arbejdsblade
Ole
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Arbejdsmetoder
• Projektet blev delt op i flere mindre dele
• Hver del blev undersøgt og behandlet af 1-3 personer
• Dele og grupper blev løbende revideret
• Alle undersøgelser og behandlinger blev beskrevet i arbejdsblade
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• Envelope and excitation evaluation• Listening test• Overview of the human speech system• Framing and deframing• LPC modeling of vocal tract
• Vector Quantization• Codebook training• Generating the codebook for speech enhancement• The K-means Clustering Algorithm
• Excitation extension• Cepstral signal analysis for pitch detection• Pitch detection• Telephone filter• Reflection Coefficients• Line Spectrum Pairs
LPsynthesis
Envelopeextension
LPanalysis
LPestimation
Excitationextension
Codebook
Arbejdsblade
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Envelope
Brian
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Envelope
• Vocal tract model
• Line Spectrum Frequency
• Codebook
• Spectral distortion
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Vocal tract model
W
-
+
FIR
Impuls generator/ white noise
1
H(z)
Predictions error filterVocal tract model
( )n-1u n | U
(u n)
(u n- 1)
(v n) (e n)
-1z
Sound production
H(z)
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Line Spectrum Frequency
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Final codebook
Narrow bandtraining data
K-meansNarrow band
codebook(2048 x 10)
Wide bandtraining data
IndexWide bandcodebook
(2048 x 20)
Codebook
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Spectral distortion
Mål : Spectral distortion < 1dB
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Excitation
Jakob
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• Ønsket funktionalitet
• Filtrering og opsampling
• Rekonstruktion af residualsignal
Excitation Extension
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• Rekonstrueret residualsignal lig originalt
• Genskabe amplitudespektrum
• Karakteristika
• Filtreringsproblem
Ønsket funktionalitet
0 1000 2000 3000 4000 5000 6000 7000 80000
0.5
1
1.5
2
Frequency
Am
plit
ud
e
0 1000 2000 3000 4000 5000 6000 7000 80000
0.5
1
1.5
2
Frequency
Am
plit
ud
e
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• Telefilter
-HP-filter: fp = 300 Hz fs = 250 Hz
-LP-filter: fp = 3400 Hz fs = 3450 Hz
Filtrering og opsampling
• Residualfilter
-HP-filter: fp = 350 Hz fs = 300 Hz
-LP-filter: fp = 3350 Hz fs = 3400 Hz
4
f [kHz]
2
Am
plitude
4
f [kHz]
2
Am
plitude
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• Modulation
• Addition af hvid støj
Rekonstruktion
Upsample &Filtering
exp(jn)
HP-filter
Excitationsignal Output
HP-filter
Whitenoise
Pitchdetector
Sinegenerator
Speechsignal
G1
G2
G3
84 6
f [kHz]
2
Am
plitude
84 6
f [kHz]
2
Am
plitude
84 6
f [kHz]
2
Am
plitude
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• Addering af pitchfrekvens
• Tilpasning af fase
• Problem ved segmentoverlap
Rekonstruktion
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
Forbedringer
• Midling af pitch
• Kalman-filter
• Pitchdetektion af svage signaler
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Gennemgang af artikel
Bjarke
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Gennemgang af artikel
Abstract Introduktion Metoder Resultater Diskussion / konklusion
Gennemgang• IMRaD
• Indhold og opbygning af afsnit
• Videnskabelig fremgangsmetode(r)
• Særlig fokus på resultater / konklusion
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Gennemgang af artikelArtiklens opbygning
Problemstilling
Undersøgelse af løsnings-metoder
Valg af løsnings-metode
Anvendelse af nye / kombination af eksisterende metoder
Videnskabelig gen-nemgang af metoder
Test metoder og resultater af tests
Vurdering af resultater
Konklusion
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Gennemgang af artikel
Abstract Introduktion Metoder Resultater Diskussion / konklusion
Indhold• Kort beskrivelse af problemstilling
• Anvendte metoder i løsning
• Resultat
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Gennemgang af artikel
Problemstilling• Telefonsystem båndbrede begrænset (300-3400 Hz)
• Mål: Båndbrede på 80-8000 Hz
Løsning• Undersøgt eksisterende løsninger / ideer
- Problemstilling ikke løst
• Arbejde videre med eksisterende idé
• Mål: Finde / forbedre metoder til implementering af idé
Abstract Introduktion Metoder Resultater Diskussion / konklusion
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Gennemgang af artikel
Eksisterende metoder• Anvendelse af metoder
• Kombination af metoder
Nye ideer• LPC LSF koefficienter
• Anvendelse af kodebog
• Modulation af residual signal
Abstract Introduktion Metoder Resultater Diskussion / konklusion
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Gennemgang af artikel
Test metoder• Matematisk - Talstørrelse for godhed
• Visuelt - Identificering af mangler
• Lyttetest - Overordnet resultat
Mål med test• Sammenligne resultater
• Identificering af problemer i metoder
• Brugeres vurdering af metoder
Abstract Introduktion Metoder Resultater Diskussion / konklusion
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Vurdering af resultater• Matematiske resultater
• Visuelle resultater
• Lyttetest resultater
Konklusion• Båndbredeudvidelse opnået
• Metoder mangler videre udvikling
Gennemgang af artikel
Abstract Introduktion Metoder Resultater Diskussion / konklusion
• Spectral Distortion
- 5,3 < μ < 7,0 dB
- 2,4 < σ2 < 7,4 dB2
- Ingen spectral transparency (1,0 dB)
• Forklaringer
- Kodebog er mangelfuld
- Sammenhæng mellem bånd utilstrækkelig
• Spectrogrammer
- Tilføjet komponenter til øvre bånd
- Unvoiced lyd gengives ultilstrækkeligt i øvre bånd
- Sinus element tilføjet upræcist i nedre bånd
• Forklaringer
- Envelope extension virker utilstrækkelig i øvre bånd
- Excitation extension virker utilstrækkelig i nedre bånd
• A/B test
- Original telefon signal fortrukket
• Forklaringer
- Artefakter introduceret i signal
- Utiltrækkelig gengivelse af unvoiced lyd
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