Course Presentation
Multimedia Systems
Speech II
Mahdi Amiri
February 2011
Sharif University of Technology
Adaptive DPCM (ADPCM)
Idea
Problem?
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Multimedia Systems, Speech II
Adaptive DPCM (ADPCM)
Size of Quantization Step
ADM: [n ]  M [n  1]
P  2, Q  1
2
M  P  1 if c [n ]  c [n  1]
M  Q  1 if c [n ]  c [n  1]
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Multimedia Systems, Speech II
Speech Compression Concepts
FFT, No Time Localization
Speech Signal
Joseph Fourier, 1768-1830
FFT
(is only localized in frequency)
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Multimedia Systems, Speech II
Speech Compression Concepts
STFT
Speech Signal
Dennis Gabor, 1900-1979
STFT
(fixed time and frequency localization)
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Multimedia Systems, Speech II
Speech Compression Concepts
Spectrogram
3D surface spectrogram of a part
from a music piece.
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Multimedia Systems, Speech II
Speech Compression Concepts
Spectrogram
Spectrogram of a male voice saying ‘nineteenth century’.
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Multimedia Systems, Speech II
Speech Compression Concepts
Spectrogram, Demonstration
Bat Echolocation Call
Flute by Jean Pierre Rampal
Face!
Singing Voice
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Multimedia Systems, Speech II
Speech Compression Concepts
Formant
The time and frequency domain
presentation of vowels /a/, /i/, and /u/
/a/
/i/
/u/
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Multimedia Systems, Speech II
Speech Compression Concepts
Sample Application
A computing system to answer
questions posed in natural language
www-943.ibm.com/innovation/us/watson/
Dr. David Ferrucci, Watson Principal Investigator
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Jeopardy! champions Ken Jennings (left) and Brad Rutter (right) versus the IBM computer Watson
Multimedia Systems, Speech II
Linear Predictive Coding (LPC)
Modeling
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Multimedia Systems, Speech II
Linear Predictive Coding (LPC)
Modeling (Hiss or Buzz)
Buzzer  Filter
Chuncks: 30 thr. 50 frames/sec.
Speech = Formants + Residue
P
Predictor for each frame:
x [n ]   ai x [n  i ]
i 1
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Multimedia Systems, Speech II
Linear Predictive Coding (LPC)
Modeling (Hiss or Buzz)
The human vocal tract as an infinite impulse response (IIR) system
LPC Block Diagram
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Multimedia Systems, Speech II
Vowel /a/
Linear Predictive Coding (LPC)
Original Paper, Atal-Hanauer 1971
Original
Synthetic
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
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Multimedia Systems, Speech II
Linear Predictive Coding (LPC)
Voiced Frame Example
Original
Synthetic
Time Domain
180 samples, Pitch period: 75
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Multimedia Systems, Speech II
Frequency Domain
Linear Predictive Coding (LPC)
Unvoiced Frame Example
Original
Synthetic:
White noise
with uniform
distribution
Time Domain
180 samples
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Multimedia Systems, Speech II
Frequency Domain
Code Excited Linear Prediction
CELP
Problem of LPC
Where there is both Hiss and Buzz
Solution
Encoder
Encode residue
Method
Vector Quantization
(Codebook)
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Decoder
Multimedia Systems, Speech II
Vector Quantization
Block Diagram
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Multimedia Systems, Speech II
Vector Quantization
Example
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Multimedia Systems, Speech II
Vector Quantization
Codebook Design
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Multimedia Systems, Speech II
Comparison of Speech Coders
Sample Speech
A lathe is a big tool. Grab every dish of sugar.
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Multimedia Systems, Speech II
Comparison of Speech Coders
Demonstration
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Original
ADPCM
LPC
CELP
Multimedia Systems, Speech II
Speech Coding
ITU-T Standards
G.711
PCM
u-law, a-law
64, 80 and 96 kbps
G.722
Check out a complete list at
http://en.wikipedia.org/wiki/List_of_codecs#Audio_codecs
A comparison of Internet audio compression formats
http://www.sericyb.com.au/audio.html
ADPCM
48, 56 and 64 kbps
G.728
A form of CELP
16 kbps
Vocoders
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Multimedia Systems, Speech II
Speech Coding
Free and Open Source Code
HawkVoice
http://hawksoft.com/hawkvoice/
Check out voice samples of HawkVoice™ codecs at
http://hawksoft.com/hawkvoice/codecs.shtml
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Multimedia Systems, Speech II
Multimedia Systems
Speech II
Thank You
Next Session: Entropy Coding
FIND OUT MORE AT...
1. http://ce.sharif.edu/~m_amiri/
2. http://www.dml.ir/
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Multimedia Systems, Speech II