diff options
| author | Marin Ivanov <[email protected]> | 2025-07-25 10:17:14 +0300 |
|---|---|---|
| committer | Marin Ivanov <[email protected]> | 2026-01-18 20:09:26 +0200 |
| commit | 0168586485e6310c598713c911b1dec5618d61a1 (patch) | |
| tree | 6aabc2a12ef8fef70683f5389bea00f948015f77 /octave/gen_rn_coeffs.m | |
* codec2 cut-down version 1.2.0
* Remove codebook and generation of sources
* remove c2dec c2enc binaries
* prepare for emscripten
Diffstat (limited to 'octave/gen_rn_coeffs.m')
| -rw-r--r-- | octave/gen_rn_coeffs.m | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/octave/gen_rn_coeffs.m b/octave/gen_rn_coeffs.m new file mode 100644 index 0000000..bfc214e --- /dev/null +++ b/octave/gen_rn_coeffs.m @@ -0,0 +1,40 @@ +% gen_rn_coeffs.m +% David Rowe 13 april 2012 +% +% Generate root raised cosine (Root Nyquist) filter coefficients +% thanks http://www.dsplog.com/db-install/wp-content/uploads/2008/05/raised_cosine_filter.m + +function coeffs = gen_rn_coeffs(alpha, T, Rs, Nsym, M) + + Ts = 1/Rs; + + n = -Nsym*Ts/2:T:Nsym*Ts/2; + Nfilter = Nsym*M; + Nfiltertiming = M+Nfilter+M; + + sincNum = sin(pi*n/Ts); % numerator of the sinc function + sincDen = (pi*n/Ts); % denominator of the sinc function + sincDenZero = find(abs(sincDen) < 10^-10); + sincOp = sincNum./sincDen; + sincOp(sincDenZero) = 1; % sin(pix/(pix) =1 for x =0 + + cosNum = cos(alpha*pi*n/Ts); + cosDen = (1-(2*alpha*n/Ts).^2); + cosDenZero = find(abs(cosDen)<10^-10); + cosOp = cosNum./cosDen; + cosOp(cosDenZero) = pi/4; + gt_alpha5 = sincOp.*cosOp; + Nfft = 4096; + GF_alpha5 = fft(gt_alpha5,Nfft)/M; + + % sqrt causes stop band to be amplified, this hack pushes it down again + + for i=1:Nfft + if (abs(GF_alpha5(i)) < 0.02) + GF_alpha5(i) *= 0.001; + endif + end + GF_alpha5_root = sqrt(abs(GF_alpha5)) .* exp(j*angle(GF_alpha5)); + ifft_GF_alpha5_root = ifft(GF_alpha5_root); + coeffs = real((ifft_GF_alpha5_root(1:Nfilter))); +endfunction |