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2000/10/31Chin-Kai Wu, CS, NTHU1 The Effect of Waveform Substitution on the Quality of PCM Packet Communications Ondria J. Wasem, David J. Goodman, Charles.

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Presentation on theme: "2000/10/31Chin-Kai Wu, CS, NTHU1 The Effect of Waveform Substitution on the Quality of PCM Packet Communications Ondria J. Wasem, David J. Goodman, Charles."— Presentation transcript:

1 2000/10/31Chin-Kai Wu, CS, NTHU1 The Effect of Waveform Substitution on the Quality of PCM Packet Communications Ondria J. Wasem, David J. Goodman, Charles A. Dvorak, Howard G. Page

2 2000/10/31Chin-Kai Wu, CS, NTHU2 Outline Introduction Signal Processing Conditions Test Results Conclusion

3 2000/10/31Chin-Kai Wu, CS, NTHU3 Introduction Techniques Silence Substitution (Zero Stuffing) Packet Repetition Pattern Matching Replicate prior pitch waveform Operations Classify transmission gaps as missing packets or silent intervals. Storage of a period of received speech. Signal Processing to extract from stored speech to replace the missing packets.

4 2000/10/31Chin-Kai Wu, CS, NTHU4 Signal Processing Conditions Packet duration – 16ms, Sampling rate – 8kHz. Silence substitution (Zero Stuffing) Packet Repetition

5 2000/10/31Chin-Kai Wu, CS, NTHU5 Signal Processing Conditions (Pattern Matching – One Sided) Missing Packet (16 ms)Search Window (16 ms) Template (4 ms) Search Match! Candidate Matching Criterion : minimum normalized absolute difference Multiply the candidate a constant that makes mean-square value equals to that of the most recently received packet

6 2000/10/31Chin-Kai Wu, CS, NTHU6 Signal Processing Conditions (Pattern Matching – Two Sided) Missing Packet (16 ms) Template (2 ms)Search Match! Matching Criterion : minimum normalized absolute difference Weighted Sum of two candidates for substitution Search Window (8 ms) Template (2 ms)Search Match!

7 2000/10/31Chin-Kai Wu, CS, NTHU7 Signal Processing Conditions (Pitch Waveform Replication) Determine whether the speech before the missing packet is voiced or not. If not voiced, the previous packet is used for substitution. Otherwise, computes a pitch period (T samples) and the substitution waveform consists of successive repetitions of the last T samples of received speech.

8 2000/10/31Chin-Kai Wu, CS, NTHU8 Test Results Complexity

9 2000/10/31Chin-Kai Wu, CS, NTHU9 Test Results (Cont’d) 2.5510

10 2000/10/31Chin-Kai Wu, CS, NTHU10 Conclusion


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