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I don't like adjusting the rational approximation - it changes (even if only nominally) the effective ratio based on quality. I think this is more appropriate

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This commit is contained in:
Chris Cannam
2022-08-08 16:55:53 +01:00
parent 6ecc973d41
commit f027a59fa4
2 changed files with 19 additions and 10 deletions
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27
src/common/BQResampler.cpp
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@@ -122,7 +122,7 @@ BQResampler::QualityParams::QualityParams(Quality q)
k_snr = 70.0;
k_transition = 0.2;
cut = 0.9;
rational_max = 48000;
length_max = 576000;
break;
case FastestTolerable:
p_multiple = 62;
@@ -130,7 +130,7 @@ BQResampler::QualityParams::QualityParams(Quality q)
k_snr = 90.0;
k_transition = 0.05;
cut = 0.975;
rational_max = 96000;
length_max = 1024000;
break;
case Best:
p_multiple = 122;
@@ -138,7 +138,7 @@ BQResampler::QualityParams::QualityParams(Quality q)
k_snr = 100.0;
k_transition = 0.01;
cut = 0.995;
rational_max = 192000;
length_max = 0;
break;
}
}
@@ -378,12 +378,7 @@ BQResampler::pick_params(double ratio) const
{
// Farey algorithm, see
// https://www.johndcook.com/blog/2010/10/20/best-rational-approximation/
int max_denom;
if (m_dynamism == RatioMostlyFixed) {
max_denom = 192000;
} else {
max_denom = m_qparams.rational_max;
}
int max_denom = 192000;
double a = 0.0, b = 1.0, c = 1.0, d = 0.0;
double pa = a, pb = b, pc = c, pd = d;
double eps = 1e-9;
@@ -500,6 +495,20 @@ BQResampler::state_for_ratio(BQResampler::state &target_state,
target_state.filter_length =
int(parameters.peak_to_zero * m_qparams.p_multiple + 1);
if (m_qparams.length_max > 0 &&
target_state.filter_length > m_qparams.length_max) {
int reduced_multiple =
int(floor(double(m_qparams.length_max) / parameters.peak_to_zero));
int reduced_length =
int(parameters.peak_to_zero * reduced_multiple + 1);
if (m_debug_level > 0) {
cerr << "BQResampler: reducing filter length from "
<< target_state.filter_length << " to "
<< reduced_length << " based on quality settings" << endl;
}
target_state.filter_length = reduced_length;
}
if (target_state.filter_length % 2 == 0) {
++target_state.filter_length;
}

2
src/common/BQResampler.h
View File

@@ -71,7 +71,7 @@ private:
double k_snr;
double k_transition;
double cut;
int rational_max;
int length_max;
QualityParams(Quality);
};