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Adds automatic bandwidth detection

Haven't tested it much and not sure not to use it without risk
for high-quality streams that may change bandwidth

--- a/src/analysis.c

+++ b/src/analysis.c

@@ -80,6 +80,7 @@

    float prev_tonality;

    float E[NB_FRAMES][NB_TBANDS];

    float lowE[NB_TBANDS], highE[NB_TBANDS];

+   float meanE[NB_TBANDS], meanRE[NB_TBANDS];

    float mem[32];

    float cmean[8];

    float std[9];

@@ -90,6 +91,7 @@

    int last_music;

    int last_transition;

    int count;

+   int opus_bandwidth;

 } TonalityAnalysisState;

 void tonality_analysis(TonalityAnalysisState *tonal, AnalysisInfo *info, CELTEncoder *celt_enc, const opus_val16 *x, int C)

@@ -115,13 +117,17 @@

     float frame_stationarity;

     float relativeE;

     float frame_prob;

-    float alpha, alphaE;

+    float alpha, alphaE, alphaE2;

     float frame_loudness;

+    float bandwidth_mask;

+    int bandwidth=0;

+    float bandE[NB_TBANDS];

     celt_encoder_ctl(celt_enc, CELT_GET_MODE(&mode));

     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);

     if (tonal->count<4)

        tonal->music_prob = .5;

@@ -201,6 +207,7 @@

     info->boost_amount[0]=info->boost_amount[1]=0;

     info->boost_band[0]=info->boost_band[1]=0;

     frame_loudness = 0;

+    bandwidth_mask = 0;

     for (b=0;b<NB_TBANDS;b++)

     {

        float E=0, tE=0, nE=0;

@@ -214,11 +221,19 @@

           tE += binE*tonality[i];

           nE += binE*2*(.5-noisiness[i]);

        }

+       bandE[b] = E;

        tonal->E[tonal->E_count][b] = E;

        frame_noisiness += nE/(1e-15+E);

        frame_loudness += sqrt(E+1e-10);

        /* Add a reasonable noise floor */

+       tonal->meanE[b] = (1-alphaE2)*tonal->meanE[b] + alphaE2*E;

+       tonal->meanRE[b] = (1-alphaE2)*tonal->meanRE[b] + alphaE2*sqrt(E);

+       /* 13 dB slope for spreading function */

+       bandwidth_mask = MAX32(.05*bandwidth_mask, E);

+       /* Checks if band looks like stationary noise or if it's below a (trivial) masking curve */

+       if (tonal->meanRE[b]*tonal->meanRE[b] < tonal->meanE[b]*.95 && E>.1*bandwidth_mask)

+          bandwidth = b;

        logE[b] = log(E+1e-10);

        tonal->lowE[b] = MIN32(logE[b], tonal->lowE[b]+.01);

        tonal->highE[b] = MAX32(logE[b], tonal->highE[b]-.1);

@@ -260,6 +275,7 @@

        }

        tonal->prev_band_tonality[b] = band_tonality[b];

     }

+

     frame_loudness = 20*log10(frame_loudness);

     tonal->Etracker = MAX32(tonal->Etracker-.03, frame_loudness);

     tonal->lowECount *= (1-alphaE);

@@ -369,5 +385,20 @@

        printf("%f ", features[i]);

     printf("\n");*/

+    /* FIXME: Can't detect SWB for now because the last band ends at 12 kHz */

+    if (bandwidth == NB_TBANDS-1 || tonal->count<100)

+    {

+       tonal->opus_bandwidth = OPUS_BANDWIDTH_FULLBAND;

+    } else {

+       int close_enough = 0;

+       if (bandE[bandwidth-1] < 3000*bandE[NB_TBANDS-1] && bandwidth < NB_TBANDS-1)

+          close_enough=1;

+       if (bandwidth<=11 || (bandwidth==12 && close_enough))

+          tonal->opus_bandwidth = OPUS_BANDWIDTH_NARROWBAND;

+       else if (bandwidth<=13)

+          tonal->opus_bandwidth = OPUS_BANDWIDTH_MEDIUMBAND;

+       else if (bandwidth<=15 || (bandwidth==16 && close_enough))

+          tonal->opus_bandwidth = OPUS_BANDWIDTH_WIDEBAND;

+    }

     info->valid = 1;

 }