2. RECONSTRUCTION OF MISSING PACKETS FOR CELP-BASED SPEECH CODERS Aamir Husain and Vladimir Cuperman School of Engineering Science, Simon Fraser University 1995 IEEE Hung, Kuo-EnNTHU/CS, Visual Communication Lab.

3. Outline Introduction System Overview Packet Reconstruction model Spectral extrapolation Simulation results Implementation

4. Introduction Jayant – odd-even sample interpolation in PCM and DPCM systems. Goodman – waveform substitution techniques such as pattern matching in PCM systems. Erdol – waveform substitution based on interpolative techniques on short-time energy parameters in PCM systems. Leung – vector linear prediction in voiced frame reconstruction in CELP coders over frame relay networks.

5. System Overview Base on LD-CELP 16kb/s standard (G.728) Variable rate CELP coder (VAR-CELP) Frame Classifier voiced, unvoiced, transition, silence Switch three distinct codec configuration 8.0 kb/s for voiced and transition frames 4.3 kb/s for unvoiced frames 667 b/s for silence

6. Packet Reconstruction Model

7. Spectral Extrapolation

8. Simulation Results

9. Implementation Pitch Estimation

10. Frame(n-1)Frame(n) Recovery Method

11. Simulation Result (original) Original Speech

12. Simulation Result (erasure) Erasure Speech (20% lost rate)

13. Simulation Result (recovery) Recovery Speech

14. Result Compare original erasurerecovery