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Slight simplification of the bandwidth detection code

New code is especially easier to justify

--- a/src/analysis.c

+++ b/src/analysis.c

@@ -225,7 +225,7 @@

     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 @@

     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 @@

                      + 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)