Ch5-Speech&amp;Audio_Coding_Examples

# Ch5-Speech&amp;Audio_Coding_Examples - Speech& Audio...

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Unformatted text preview: Speech & Audio Processing Speech & Audio Coding Examples 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 February 11, 2012 Veton Këpuska 3 Windowing Analysis Stage N – Length of the Analysis Window 10-30 msec February 11, 2012 Veton Këpuska 4 Some Analysis Windows 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 . sin 2 sin window sine 5 . sin 2 + = + = N n n w N n n w π π π 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. 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 February 11, 2012 Veton Këpuska 8 Analysis of Quantization Errors...
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Ch5-Speech&amp;Audio_Coding_Examples - Speech& Audio...

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