From 6862b44e7d6500765dad4bf19e3c21423901802a Mon Sep 17 00:00:00 2001
From: Jean-Marc Valin <jmvalin@jmvalin.ca>
Date: Mon, 13 May 2013 22:35:09 -0400
Subject: [PATCH] Slight simplification of the bandwidth detection code
New code is especially easier to justify
---
src/analysis.c | 24 +++++++++++-------------
1 file changed, 11 insertions(+), 13 deletions(-)
diff --git a/src/analysis.c b/src/analysis.c
index 7dc792bbc..b978b6e05 100644
--- a/src/analysis.c
+++ b/src/analysis.c
@@ -225,7 +225,7 @@ void tonality_analysis(TonalityAnalysisState *tonal, AnalysisInfo *info_out, con
tonal->last_transition++;
alpha = 1.f/IMIN(20, 1+tonal->count);
alphaE = 1.f/IMIN(50, 1+tonal->count);
- alphaE2 = 1.f/IMIN(6000, 1+tonal->count);
+ alphaE2 = 1.f/IMIN(1000, 1+tonal->count);
if (tonal->count<4)
tonal->music_prob = .5;
@@ -375,8 +375,7 @@ void tonality_analysis(TonalityAnalysisState *tonal, AnalysisInfo *info_out, con
bandwidth_mask = 0;
bandwidth = 0;
- for (b=0;b<NB_TOT_BANDS;b++)
- maxE = MAX32(maxE, tonal->meanE[b]);
+ maxE = 0;
noise_floor = 5.7e-4f/(1<<(IMAX(0,lsb_depth-8)));
noise_floor *= noise_floor;
for (b=0;b<NB_TOT_BANDS;b++)
@@ -392,19 +391,18 @@ void tonality_analysis(TonalityAnalysisState *tonal, AnalysisInfo *info_out, con
+ out[i].i*out[i].i + out[N-i].i*out[N-i].i;
E += binE;
}
- E /= (band_end-band_start);
maxE = MAX32(maxE, E);
- if (tonal->count>2)
- {
- tonal->meanE[b] = (1-alphaE2)*tonal->meanE[b] + alphaE2*E;
- } else {
- tonal->meanE[b] = E;
- }
+ tonal->meanE[b] = MAX32((1-alphaE2)*tonal->meanE[b], E);
E = MAX32(E, tonal->meanE[b]);
- /* 13 dB slope for spreading function */
+ /* Use a simple follower with 13 dB/Bark slope for spreading function */
bandwidth_mask = MAX32(.05f*bandwidth_mask, E);
- /* Checks if band looks like stationary noise or if it's below a (trivial) masking curve */
- if (E>.1*bandwidth_mask && E*1e10f > maxE && E > noise_floor)
+ /* Consider the band "active" only if all these conditions are met:
+ 1) less than 10 dB below the simple follower
+ 2) less than 90 dB below the peak band (maximal masking possible considering
+ both the ATH and the loudness-dependent slope of the spreading function)
+ 3) above the PCM quantization noise floor
+ */
+ if (E>.1*bandwidth_mask && E*1e9f > maxE && E > noise_floor*(band_end-band_start))
bandwidth = b;
}
if (tonal->count<=2)
--
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