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Effect of the Phase on Effect of the Phase on Speech and Musical Speech and Musical signals using DWT signals using DWT
By:By:Hafiz, MalikHafiz, Malik
ECE418,DSPIIECE418,DSPIISpring,02Spring,02
Talk outlineTalk outline
IntroductionIntroduction Block DiagramBlock Diagram ResultsResults ApplicationsApplications conclusionconclusion
IntroductionIntroduction
What is Phase and phase-shift?What is Phase and phase-shift? Effect of the phase on the signals?Effect of the phase on the signals? How to play with phase?How to play with phase?
What is phase & phase shift?What is phase & phase shift?
Start/peak location of a signal with certain Start/peak location of a signal with certain reference. reference.
Phase shift is nothing more than a temporal shift.Phase shift is nothing more than a temporal shift.
The red curve is the original signal, the blue one is the signal that has been phase-shifted; in black, the result of adding these two.
Effect of the phase-shift on the Effect of the phase-shift on the mixed signalsmixed signals
XXresultresult = = XXorignalorignal+ + XXshiftshift
when summing two identical signals, one phase-shifted a when summing two identical signals, one phase-shifted a few milliseconds vs. the other, some frequencies will be few milliseconds vs. the other, some frequencies will be amplified, some others will be attenuated.amplified, some others will be attenuated.
The higher in the frequency spectrum, the more noticeable The higher in the frequency spectrum, the more noticeable
the changes in the resulting sound.the changes in the resulting sound.
All-Pass Systems and their All-Pass Systems and their applicationsapplications
What are All-Pass Filters ?What are All-Pass Filters ? Can I use All-Pass Filters to shift the Can I use All-Pass Filters to shift the
Phase….???Phase….??? Yes! Why not…Yes! Why not…
Overview of All-pass systems Overview of All-pass systems
• Pole-Zero
• Magnitude • Phase
How to play with phase???How to play with phase???
1.1. Using Transformed domain i.e. Using Transformed domain i.e. FT,CT, etcFT,CT, etc
2.2. Using all-Pass filtersUsing all-Pass filters
Block DiagramBlock Diagram
Output Audio
waveletAnalysis
Filterbank
All-Pass system
waveletsynthesis
Filterbank
Input Audio
Wavelet Analysis/SynthesisWavelet Analysis/Synthesis Filter Banks with phase shift system Filter Banks with phase shift system
output audio with embedded
data
HPF
LPF
APF
LPF
LPFLPF
APF
HPFAPF
Data hiding
Input audio
Result: Result: Using All-Pass filters & DWTUsing All-Pass filters & DWT
cDs & cA Superimposed coef.
Result2: Result2: Using All-Pass filters & DWTUsing All-Pass filters & DWT
A8 & D8 onlyD1 only
Results….Results….
D8 & A8 D1 only With all
original
Musical signal
Results… Results…
original
With allD1 onlyA8 & D8
Audio signal
Magnitude Response due to phase-Magnitude Response due to phase-shiftshift
original D8 only
A8 & D8With all
ApplicationsApplications
Data HidingData Hiding1.1. WatermarkingWatermarking
2.2. CaptioningCaptioning
Hiding signature to the songsHiding signature to the songs Hiding signature to the imagesHiding signature to the images
Future DirectionFuture Direction
More sophisticated system for data hiding can be More sophisticated system for data hiding can be developed with out deteriorating the quality of developed with out deteriorating the quality of the audio by exploiting the fact that human the audio by exploiting the fact that human perception is bit insensitive to certain bands of perception is bit insensitive to certain bands of frequency. frequency.
This thing can be done by frequency selective This thing can be done by frequency selective phase-shifting.phase-shifting.
This method i.e. frequency selective phase-This method i.e. frequency selective phase-shifting will also work for images as well as video.shifting will also work for images as well as video.
Thanks!!!!Thanks!!!!
Hafiz, MalikHafiz, Malik
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