Lec04, Speech II, v1.06.ppt - ce.sharif.educe.sharif.edu/courses/91-92/2/ce342-1/resources... ·...

Multimedia SystemsMultimedia Systems

Speech IISpeech II

Course PresentationCourse Presentation

Mahdi Amiri

February 2013

Sharif University of Technology

Speech Compression

Based on Time Domain analysis

Differential Pulse-Code Modulation (DPCM)

Adaptive DPCM (ADPCM)

Road MapRoad Map

Page 1 Multimedia Systems, Speech II

Based on Frequency Domain analysis

Linear Predictive Coding (LPC)

Code Excited Linear Prediction (CELP)

Differential PCM (DPCM)IdeaIdea

Take advantage of data redundancy


[… 110 112 111 112 112 114 115 115 114 114… ] [… +2 -1 +1 0 +2 +1 0 -1 0 …]

Or histogram of PCM samples in a chunk

of digitized audio.

Differential PCM (DPCM)Basic SchemeBasic Scheme

General Predictive Coding


1Delta Modulation (DM): i n ia x z

−

−⇒∑

Problem?

Differential PCM (DPCM)Error PropagationError Propagation

General Predictive Coding


The output of dequantizer in decoder is not equal with the input of the

quantizer in the encoder � The input of predictor in decoder is not the

same as input values of predictor in encoder � This is the source of error

propagation.

Differential PCM (DPCM)Better StructureBetter Structure


Adaptive DPCM (ADPCM)IdeaIdea


Problem?

Adaptive DPCM (ADPCM)Size of Quantization StepSize of Quantization Step

Delta Modulation (DM)

1 bit quantizer: 0 means + and 1 means ∆ −∆


ADM: [ ] [ 1]n M n∆ = ∆ −

12, 2

P Q= =

1 if [ ] [ 1]

1 if [ ] [ 1]

M P c n c n

M Q c n c n

= > = −

= < ≠ −

Adaptive Delta Modulation (ADM)

Speech Compression ConceptsFFT, No Time LocalizationFFT, No Time Localization

Speech Signal


FFT

(is only localized in frequency)

Joseph Fourier, 1768-1830

Speech Compression ConceptsFFT, No Time LocalizationFFT, No Time Localization


See Power Spectral Density (PSD) examples in MATLAB

Speech Compression ConceptsSTFTSTFT

Speech Signal


STFT

(fixed time and frequency localization)

Dennis Gabor, 1900-1979

Speech Compression ConceptsSpectrogramSpectrogram


3D surface spectrogram of a part

from a music piece.

Speech Compression ConceptsSpectrogramSpectrogram


Spectrogram of a male voice saying ‘nineteenth century’.

Speech Compression ConceptsSpectrogram Display in Spectrogram Display in AudaCityAudaCity


Waveform

Spectrogram

Speech Compression ConceptsSpectrogram, DemonstrationSpectrogram, Demonstration

Bat Echolocation Call Flute by Jean Pierre Rampal


Bat Echolocation Call Flute by Jean Pierre Rampal

Singing Voice Face!

Speech Compression ConceptsFormantFormant


The time and frequency domain

presentation of vowels /a/, /i/, and /u//a/

/i/

/u/

Speech Compression ConceptsSample ApplicationSample Application

A computing system to answer

questions posed in natural language


Jeopardy! champions Ken Jennings (left) and Brad Rutter (right) versus the IBM computer Watson

www-943.ibm.com/innovation/us/watson/

Dr. David Ferrucci, Watson Principal Investigator

Linear Predictive Coding (LPC)ModelingModeling


Linear Predictive Coding (LPC)Modeling (Hiss or Buzz)Modeling (Hiss or Buzz)

Buzzer � Filter

Speech = Formants + Residue

Chuncks: 30 thr. 50 frames/sec.


1

[ ] [ ]P

i

i

x n a x n i=

= −∑ɶPredictor for each frame:

Speech = Formants + Residue

Linear Predictive Coding (LPC)Modeling (Hiss or Buzz)Modeling (Hiss or Buzz)

The human vocal tract as an infinite impulse response (IIR) system Vowel /a/


LPC Block Diagram

Linear Predictive Coding (LPC)Original Paper, Original Paper, AtalAtal--HanauerHanauer 19711971

Original


Comparison of wide-band sound spectrograms for synthetic and original speech signal for the utterance "It's

time we rounded up that herd of Asian cattle," spoken by a male speaker

Original

Synthetic

Linear Predictive Coding (LPC)Voiced Frame ExampleVoiced Frame Example

Original


Synthetic

Time Domain Frequency Domain

180 samples, Pitch period: 75

Linear Predictive Coding (LPC)Unvoiced Frame ExampleUnvoiced Frame Example

Original


Synthetic:

White noise

with uniform

distribution

Time Domain Frequency Domain

180 samples

Code Excited Linear Prediction

Problem of LPCWhere there is both Hiss and Buzz

Solution

CELPCELP

Encoder


SolutionEncode residue

MethodVector Quantization

(Codebook)Decoder

Vector QuantizationBlock DiagramBlock Diagram


Vector QuantizationExampleExample

Sample scalar quantizer

We have 3 possible colors for

each square; so we can quantize

each square with 2 bits � (28 *

2 = 56 bits for all 28 (7*4)

squares.


squares.

Sample vector quantizer

We have 8 forms in the

codebook; so we can quantize

each form with 3 bits � (7 * 3

= 21 bits for all 28 (7*4)

squares.Codebook

Vector QuantizationCodebook DesignCodebook Design


Comparison of Speech CodersSample SpeechSample Speech

A lathe is a big tool. Grab every dish of sugar.


Comparison of Speech CodersDemonstrationDemonstration


Original ADPCM

LPC CELP

Speech Coding

G.711

PCM

u-law, a-law

64, 80 and 96 kbps

G.722

ITUITU--T StandardsT Standards

Check out a complete list athttp://en.wikipedia.org/wiki/List_of_codecs#Audio_codecs

A comparison of Internet audio compression formats

http://www.sericyb.com.au/audio.html


G.722

ADPCM

48, 56 and 64 kbps

G.728

A form of CELP

16 kbps

Vocoders

http://www.sericyb.com.au/audio.html

Speech Coding

HawkVoice

Free and Open Source CodeFree and Open Source Code

http://hawksoft.com/hawkvoice/


Check out voice samples of HawkVoice™ codecs at

http://hawksoft.com/hawkvoice/codecs.shtml

Thank You

Multimedia SystemsMultimedia Systems

Speech IISpeech II


Thank You

1. http://ce.sharif.edu/~m_amiri/

2. http://www.dml.ir/

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