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Enhancing CELP Speech Coders: A Comprehensive Approach to Packet Reconstruction

This paper explores advanced methods for reconstructing missing packets in CELP-based speech coders, presented by Aamir Husain and Vladimir Cuperman at Simon Fraser University in 1995. We delve into the system overview, focusing on the packet reconstruction model utilizing spectral extrapolation. Key simulations reveal the effectiveness of our approach, addressing challenges faced in packet loss scenarios. Techniques from previous research, including odd-even sample interpolation and waveform substitution, are discussed alongside our implementation results and recovery measures for speech data.

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Enhancing CELP Speech Coders: A Comprehensive Approach to Packet Reconstruction

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  1. 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-En NTHU/CS, Visual Communication Lab.

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

  3. 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.

  4. 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

  5. Packet Reconstruction Model

  6. Spectral Extrapolation

  7. Simulation Results

  8. Implementation • Pitch Estimation

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

  10. Simulation Result (original) Original Speech

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

  12. Simulation Result (recovery) Recovery Speech

  13. original erasure recovery Result Compare

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