tns: prevent division-by-zero or instability on highly correlated signals#91
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fabiangreffrath merged 2 commits intoknik0:masterfrom Mar 23, 2026
Merged
tns: prevent division-by-zero or instability on highly correlated signals#91fabiangreffrath merged 2 commits intoknik0:masterfrom
fabiangreffrath merged 2 commits intoknik0:masterfrom
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libfaac/tns.c
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| } | ||
| error = error * (1 - kTemp*kTemp); | ||
| /* Prevent numerical instability or division-by-zero with highly correlated signals */ | ||
| if (error < 1e-10) error = 1e-10; |
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Why exactly 1e-10?
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It was arbitrary, I found a better solution that avoided its use
- Fixes potential division-by-zero by checking error <= 0.0 before computing reflection coefficients. - Implements a filter stability guard (|kTemp| >= error) to break recursion if the model is saturated or unstable. - Removes magic 1e-10 epsilon in favor of an early exit for perfectly predicted signals. - Returns a value above DEF_TNS_GAIN_THRESH on perfect prediction to ensure TNS is correctly triggered without math overflow.
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