From a3300d7b240e8e4ce331da8aecdfc9d2cc5c813d Mon Sep 17 00:00:00 2001
From: Jean-Marc Valin <jmvalin@jmvalin.ca>
Date: Wed, 10 Apr 2019 21:13:44 -0400
Subject: [PATCH] Fix bias in LPC spectrum
---
dnn/freq.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/dnn/freq.c b/dnn/freq.c
index c88d0715a..e04ab8585 100644
--- a/dnn/freq.c
+++ b/dnn/freq.c
@@ -47,6 +47,9 @@ static const opus_int16 eband5ms[] = {
0, 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 16, 20, 24, 28, 34, 40
};
+static const float compensation[] = {
+ 0.8f, 1.f, 1.f, 1.f, 1.f, 1.f, 1.f, 1.f, 0.666667f, 0.5f, 0.5f, 0.5f, 0.333333f, 0.25f, 0.25f, 0.2f, 0.166667f, 0.173913f
+};
typedef struct {
int init;
@@ -233,7 +236,7 @@ float lpc_from_cepstrum(float *lpc, const float *cepstrum)
RNN_COPY(tmp, cepstrum, NB_BANDS);
tmp[0] += 4;
idct(Ex, tmp);
- for (i=0;i<NB_BANDS;i++) Ex[i] = pow(10.f, Ex[i]);
+ for (i=0;i<NB_BANDS;i++) Ex[i] = pow(10.f, Ex[i])*compensation[i];
return lpc_from_bands(lpc, Ex);
}
--
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