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| Keywords: Quantization shaped dither spectrum.png en Spectrum of a 750 Hz pure tone sampled at 48 kHz and quantized to 4 bits using triangular dither and noise shaping <pre> quantization_shaped_dither m Quantization demo using shaped dither Authors Fatbag License Public domain no warranties rand 'state' 0xdeadbeef ; f_s 48000; sampling rate samples/sec f0 750; frequency of sine wave Hz t_s 1/f_s; sampling period sec/sample w0 2 pi f0; angular frequency of sine wave Hz t 0 4095 t_s; x round 16384 sin w0 t + rand 1 length t - 0 5 + rand 1 length t - 0 5 ; x zeros 1 length t ; FIR filter coefficients taken from Audacity as of 2015-11-08 h 1 2 033 -2 165 1 959 -1 590 0 6149; prev_error zeros 1 5 ; for i 1 length t ideal 15 sin w0 t i + dot h 2 end prev_error ; x i round ideal + rand - 0 5 + rand - 0 5 ; prev_error ideal - x i prev_error 1 4 ; endfor figure 1; plot t 1 ceil 2 f_s/f0 x 1 ceil 2 f_s/f0 ; axis 0 ceil 2 f_s/f0 t_s -20 20 ; grid on; xlabel 't' ; ylabel 'x t ' ; figure 2; X fft x 1 4096 ; X X 1 2048 ; m 20 log10 arrayfun norm X ; m - max m ; m ~isfinite m -1000; f 0 2047 /2048 f_s/2; plot f m ; axis 0 f_s/2 -100 0 ; grid on; xlabel 'Frequency Hz ' ; ylabel 'Relative power dB ' ; print 'quantization_shaped_dither_spectrum_uncropped png'; figure 3; stem 0 length h -1 h ; figure 4; H w freqz h ; m arrayfun norm H ; m 20 log10 m ; plot w m ; axis 0 pi -10 50 ;</pre> 2015-11-13 own Andrew D'Addesio other versions cc-zero Digital audio Quantization Uploaded with UploadWizard | ||||
