A Low Bit Rate Speech Coder Based on the Inflection Point Detection

2016

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A fixed rate speech coder based on the filter bank and the non-uniform sampling technique is proposed. The non-uniform sampling is achieved by the detection of inflection points (IPs). A speech block is band passed by the filter bank, and the subband signals are processed by the IP detector, and the detected IP patterns are compared with entries of the IP database. For each subband signal, the address of the closest member of the database and the energy of the IP pattern are transmitted through channel. In the receiver, the decoder recovers the subband signals using the received addresses and the energy information, and reconstructs the speech via the filter bank summation. As results, the coder shows fixed data rate contrary to the existing speech coders based on the non-uniform sampling. Through computer simulation, the usefulness of the proposed technique is confirmed. The signal-to-noise ratio (SNR) performance of the proposed method is comparable to that of the uniform sampled pulse code modulation (PCM) below 20 kbps data rate.

“…Otherwise, the ID value in (2) is compared to a predetermined threshold. If the value is greater than the threshold, the sample is classified as an inflection point of slope change [11].…”

Section: Inflection Point Detectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A Fixed Rate Speech Coder Based on the Filter Bank Method and the Inflection Point Detection

2016

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“…Most of non-uniform sampling based speech coders show variable code rates which are not suitable for a fixed communication channel [1][2][3][4][5][6]. Recently, a fixed rate speech coder based on the non-uniform sampling technique has been proposed in [7].…”

Section: Introductionmentioning

confidence: 99%

A Fixed Rate Speech Coder with Improved Database Search

2017

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A fixed rate speech coder having improved database search performance is proposed. In the speech coder, the 10 ms block of speech is band-passed using the filter bank, and the inflection points (IP) for each band are detected and analyzed to get the short-time statistics like the energy and IP rate. The obtained IP statistics are used to decide if the speech block is voiced or unvoiced. Then the encoder searches for the closest IP pattern either at the voiced part or at the unvoiced part of the IP database. For further reduction of the search time, the entries of the database parts corresponding to the neighboring subbands are checked for the obtained IP pattern. As results, about 94.5% decrease in search time is achieved compared to the exhaustive search. With 10 subbands and 240 entries for each band, the reconstructed signal shows about 5.2 dB SNR at 32 kbps data rate.

A Fixed Rate Speech Coder Based on the Filter Bank Method with Non-Uniform Bandwidths

2019

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A fixed rate speech coder exploiting the filter bank with non-uniform bandwidth is proposed. The speech coder is based on the inflection point (IP) detection. The speech signal is filtered by a group of bandpass filters with non-uniform bandwidths. Each bandpass filtered signal is processed by the IP detector, and the obtained IP pattern is compared with the entries of the IP pattern database. To facilitate the database search, the IP pattern entries are grouped into two kinds: IP patterns for voiced and the unvoiced speech. Before the search, the obtained IP patterns are checked if they belong to the voiced or the unvoiced. For that purpose, the shorttime energy of IP pattern from the first band is calculated and compared to the predetermined threshold value. In addition to the unvoiced/voiced decision, the non-uniform bandwidth bandpass filters are used for the filter bank to speed up the database search. By using the non-uniformly spaced bandpass filters, the number of filters in the filter bank becomes smaller. Transmitted information for each subband includes the IP pattern address of the database and amplitude of each IP pattern. In the receiver, the decoder recovers the subband signals using the received addresses and the energy information, and reconstructs the speech via the filter bank summation. Through computer simulation, the usefulness of the proposed technique is confirmed. The SNR performance of the proposed method is approximately 9 dB with relatively low bitrate of 12.8 kbps.