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In harsh channel conditions, the quality of the synthetic speech at low bit rate would be affected severely. In order to improve the robustness of the vocoder and make it more resilient to errors in random channel, unequal error protection (UEP) channel coding is usually adopted. However, when the errors cannot be corrected in some cases, UEP channel coding will not improve the quality of the synthetic...
In order to improve the channel bandwidth utilization of voice communication, a variable bit rate speech coding algorithm based on enhanced mixed excitation linear prediction (MELPe) is proposed in the paper. In voice communication, only about 40% of the time is occupied by talking, whereas the rest is engaged by silence or background noise. In addition, unvoiced frame usually requires less transmission...
This paper presents a speech protection system based on adaptive masking. The system can adaptively adjust the masking noise volume according to the Speech Intelligibility Index (SII) proposed in ANSI S3.5-1997. The volume of the masking noise is minimized by limiting SII to a low level at which the speech to be protected can not be understood. This method can effectively reduce excess masking noise...
With rapid development of information technology and upgrading of intelligent terminals, two-dimensional barcode has been widely used as a carrier to store, transfer and retrieve information. Due to the limited capacity, current two-dimensional barcodes are designed to embed text-only messages. In this paper, a generation method for acoustic two-dimensional barcode is proposed. It is based on speech...
In the underwater communication, satellite communication, secure communication and other channels, the channel bandwidth is narrow and the channel condition is relatively poor. Therefore, higher quality and lower rate speech coding is needed. In order to improve the synthetic speech quality and save channel bandwidth, voice activity detection (VAD) technique is introduced to Mixed Excitation Linear...
Low bit rate speech coding is important to speech communications over band-limited or harsh channels. In this paper, based on the mixed excitation linear prediction (MELP) model, we propose a high-quality 400bps low bit rate speech coding algorithm which introduces multi-frame joint vector quantization, adaptive spectral enhancement and multi-band sinusoidal mixed excitation. Efficient parameter quantization...
To obtain high quality synthetic speech at 2400 bps, this paper presents a vocoder based on the Mixed Excitation Linear Prediction (MELP) model. The differences of the vocoder parameters are analyzed, and an unequal error protection channel coding and a parameter substitution method for error frame are proposed to improve the robustness over random error channel. Several channel coding schemes are...
This paper proposes an algorithm improved over MMSE-LSA Algorithm. It suits non-stationary noise environments better than the traditional algorithm. The main part of this method is the estimation of noise, which is updated using time-frequency smoothing factors calculated based on speech-present probability in each frequency bin of the noisy speech spectrum. It could keep up with the noise change...
Effective quantization of pitch parameter is very important for low bit rate speech coding algorithms. Traditional method uses a constant weighting factor based distortion measure for pitch quantization based on mixed excitation linear prediction (MELP). In this paper, we propose a variable weighting factor based distortion measure for pitch quantization based on MELP. In this method, we combine several...
An algorithm based on superframe mode has been proposed to jointly optimize the multi-parameter codebook sizes in research of 0.3 Kb/s speech coding algorithm based on MELP. Codebook sizes for pitch, line spectrum frequency (LSF) and short term energy in various superframe modes are optimized together depending on the bits to quantize them. Simulation results showed that the proposed algorithm greatly...
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