Robust, low delay tree coding of speech /
| Main Author: | |
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | In this research, a low delay vector tree coder operating at 8Kbits/sec and a multi-tree coder at 9.6Kbits/sec using a novel scheme for adaptation of the short-term coefficients are developed. These tree coders are implemented with the (M,L) searching algorithm, a fixed symbol release algorithm, a modified Jayant gain adaptation algorithm, and backward adaptation for long-term and short-term predictors. The overall delay of each tree coder is maintained at 2.5 msec (16 samples at the 6.4KHz sampling frequency). These coders produce good quality speech over ideal channels, and they are very robust to channel errors up to a bit error rate (BER) of 10^-3. This robustness is achieved by using a parallel adaptation scheme in combination with the use of a smoothed version of the received excitation sequence for adaptation of the short-term prediction coefficients. The excitation sequence is smoothed with an all-zero filter whose coefficients are obtained from the truncated finite impulse response (FIR) approximation of the all-pole short-term synthesizer. Using pseudo-Gray coding as an index coding method, the robustness of the system is improved when the BER is greater than 10^-3. For each tree coder, reconstructed output speech is evaluated using signal-to-quantization noise ratios (SNR), segmental SNRs, narrow band spectrograms, and informal listening tests. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Electrical Engineering." |
| Physical Description: | xiv, 138 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |