1. Effect of the Phase on Speech and Musical signals using DWT By: Hafiz, Malik ECE418,DSPIISpring,02

2. Talk outline Introduction Introduction Block Diagram Block Diagram Results Results Applications Applications conclusion conclusion

3. Introduction 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?

4. What is phase & phase shift? Start/peak location of a signal with certain reference. Start/peak location of a signal with certain 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.

5. Effect of the phase-shift on the mixed signals X result = X orignal + X shift when summing two identical signals, one phase-shifted a few milliseconds vs. the other, some frequencies will be amplified, some others will be attenuated. when summing two identical signals, one phase-shifted a few milliseconds vs. the other, some frequencies will be amplified, some others will be attenuated. The higher in the frequency spectrum, the more noticeable the changes in the resulting sound. The higher in the frequency spectrum, the more noticeable the changes in the resulting sound.

6. All-Pass Systems and their applications What are All-Pass Filters ? What are All-Pass Filters ? Can I use All-Pass Filters to shift the Phase….??? Can I use All-Pass Filters to shift the Phase….??? Yes! Why not… Yes! Why not…

7. Overview of All-pass systems Pole-Zero Magnitude Phase

8. How to play with phase??? 1. Using Transformed domain i.e. FT,CT, etc 2. Using all-Pass filters

9. Block Diagram Output Audio wavelet Analysis Filter bank All-Pass system wavelet synthesis Filter bank Input Audio

10. Wavelet Analysis/Synthesis Filter Banks with phase shift system output audio with embedded data H PF LPF APF LPF APF HPF APF Data hiding Input audio

11. Result: Using All-Pass filters & DWT cDs & cASuperimposed coef.

12. Result2: Using All-Pass filters & DWT A8 & D8 onlyD1 only

13. Results…. D8 & A8D1 onlyWith all original Musical signal

14. Results… original With allD1 onlyA8 & D8 Audio signal

15. Magnitude Response due to phase-shift originalD8 only A8 & D8 With all

16. Applications Data Hiding Data Hiding 1. Watermarking 2. Captioning Hiding signature to the songs Hiding signature to the songs Hiding signature to the images Hiding signature to the images

17. Future Direction More sophisticated system for data hiding can be developed with out deteriorating the quality of the audio by exploiting the fact that human perception is bit insensitive to certain bands of frequency. More sophisticated system for data hiding can be developed with out deteriorating the quality of the audio by exploiting the fact that human perception is bit insensitive to certain bands of frequency. This thing can be done by frequency selective phase-shifting. This thing can be done by frequency selective phase-shifting. This method i.e. frequency selective phase- shifting will also work for images as well as video. This method i.e. frequency selective phase- shifting will also work for images as well as video.

18. Thanks!!!! Hafiz, Malik