Ch12 Speech&Audio_Coding_Examples

Ch12 Speech&Audio_Coding_Examples - Speech &...

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Speech & Audio Coding Examples
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February 11, 2012 Veton Këpuska 2 A Simple Speech Coder LPC Based Analysis Structure Pre- emphasis Windowing Analysis Auto- Correlation Levinson- Durbin Linear Prediction Analysis Audio Input Analysis Filter Residual Filter  Coeffs Residual Filter  Coeffs Quantization
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February 11, 2012 Veton Këpuska 3 Windowing Analysis Stage N – Length of the  Analysis Window 10-30 msec
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February 11, 2012 Veton Këpuska 4 Some Analysis Windows
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February 11, 2012 Veton Këpuska 5 MATLAB Useful Functions wintool Use “doc wintool” for more information window Use “>doc window” for the list of supported windows Define your own window if needed e.g: Sine window and Vorbis window [ ] ( 29 [ ] ( 29 window vorbis 5 . 0 sin 2 sin window sine 5 . 0 sin 2 + = + = N n n w N n n w π
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February 11, 2012 Veton Këpuska 6 LPC Analysis Stage LPC Method Described in: Ch5-Analysis_&_Synthesis_of_Pole- Zero_Speech_Models.ppt Summary: Perform Autocorrelation Solve system of equations with Durbin- Levinson Method MATLAB help doc lpc, etc. 
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February 11, 2012 Veton Këpuska 7 Example of MATLAB Code function myLPCCodec(wavfile, N) % % wavfile - input MS wav file % N - LPC Filter Order % [x, fs, nbits] = wavread(wavfile); % plot(x); % Playing Original Signal soundsc(x,fs); % Performing LPC analysis using MATLAB lpc function [a, g] = lpc(x,N); % performing filtering operation on estimated filter coeffs % producing predicted samples est_x = filter([0 -a(2:end)], 1, x); % error signal e = x - est_x; % Testing the quality of predicted samples soundsc(est_x, fs); % Synthesis Stage With Zero Loss of Information syn_x = filter([0 -a(2:end)], 1, g.*e); soundsc(syn_x,fs); ( 29 ( 29 z A z H 1 = ge[n] ŝ[n] [ ] [ ] [ ] = + - = p k k n ge k n s n s 1 ˆ ˆ α
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February 11, 2012 Veton Këpuska 8 Analysis of Quantization Errors Use MATLAB functions to research the effects of  quantization errors introduced by precision of the arithmetic 
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Ch12 Speech&Audio_Coding_Examples - Speech &...

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