Study On Artificial Bandwidth Extension Of Speech Signal

In fixed telephony network, the transmission of voice is narrowband voice. The sampling frequency of voice is 8KHz. Because of missing high-frequency energy, the voice sounds "thin and weak". With the emergence of wideband codec system, wideband communications are possible. However, the communication network upgrade is a complex, lengthy, gradual process, and how to access broadband voice quality quickly under the existing network becomes a urgent to solve practical problems. There is a way without changing the network structure to transport wideband speech, the way is the voice of artificial bandwidth extension.This study is based on information hiding speech bandwidth extension algorithm and presented two speech bandwidth extension algorithm. The main tasks are as follows:(1) Study the digital model of voice, learn the pre-processing, linear prediction of speech, autocorrelation of the solution and Vector quantization.(2) Extract high-frequency in time domain, frequency domain envelope parameters, the average time-domain envelope parameters and the average frequency envelope parameters, and parameter extraction compression with vector quantization. Design a method of synthetic high-frequency components using high-frequency parameters.(3) Study the characteristics and various audio watermark embedding algorithm, and improved design of the two least significant bit embedding algorithm, the compression of high-frequency information embedded in narrowband voice.(4) Study high-frequency components of G.711.1 protocol synthesis, extract the high-frequency speech MDCT coefficients, and compress the extraction coefficient.(5) Using C language for the voice bandwidth expansion method has been implemented to complete the objective testing and subjective voice quality tests, and two algorithms were compared. By simulation test, two kinds of bandwidth expansion of broadband voice synthesis algorithms have achieved the desired results. The complexity of algorithm control in a certain range, effects of wideband speech have been greatly improved than narrowband speech.