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57 lines
1.6 KiB
57 lines
1.6 KiB
% lspvar.m
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% David Rowe 8 Feb 2015
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%
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% Experiments in reducing LSP variance in order to make quantisation easier
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lsp;
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close all;
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graphics_toolkit ("gnuplot");
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function v = det_var(s)
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p = 10;
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ak=lpcauto(s,p,[160 80]);
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[rows cols] = size(ak);
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w = zeros(rows,p);
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for r=1:rows
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w(r,:) = atolsp(ak(r,:));
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end
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v = sum(var(w));
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figure;
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plot(w)
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end
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s=load_raw("../raw/cq_ref.raw");
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det_var(s)
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if 1
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Fs = 8000;
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[b a] = cheby2(6,40,[300 2600]/(Fs/2));
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s1 = filter(b,a,s);
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det_var(s1)
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end
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% + Equalise to remove spectral slope, this reduces variance of spectral
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% envelope
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% + Can probably get rid of energy for many vectors too, except flat ones?
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% + Or have some sort of correlation of gain with peakiness of vectors?
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% + Once flattened try slicing out low energy harmonics, like post filter. How
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% does this sound? Any artefacts of harmonics coming and going near
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% thresholds?
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% + BPF as well, it's all abt minimal information.
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% + What's left? Look at it. How can it be represented? Look at tol distort,
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% what quantiser will deliver that? Just position of clipped peaks?
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% + fall back HF mode, no energy, voicing, just spectral information. Diveristy
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% compared to FEC? Test with simulation of ideal code. Aux carrier with
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% extra information to get 1300-ish quality. Coherent, pilot assisted demod.
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% Low PAPR as extra carriers at lower power level. Essentially for free in
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% terms of TX power.
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% + What is a viable plan to get this going in a mon month or so?
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% + Octave equlaisation of input files
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% + take model files, simulate quantisation, back to C for synth?
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% + Coherent FDM modem port to C
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