freeswitch/libs/silk/src/SKP_Silk_detect_SWB_input.c

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/*
 * Detect SWB input by measuring energy above 8 kHz.
 */

#include "SKP_Silk_main.h"

void SKP_Silk_detect_SWB_input(
    SKP_Silk_detect_SWB_state   *psSWBdetect,   /* (I/O) encoder state  */
    const SKP_int16             samplesIn[],    /* (I) input to encoder */
    SKP_int                     nSamplesIn      /* (I) length of input */
)
{
    SKP_int     HP_8_kHz_len, i, shift;
    SKP_int16   in_HP_8_kHz[ MAX_FRAME_LENGTH ];
    SKP_int32   energy_32;

    /* High pass filter with cutoff at 8 khz */
    HP_8_kHz_len = SKP_min_int( nSamplesIn, MAX_FRAME_LENGTH );
    HP_8_kHz_len = SKP_max_int( HP_8_kHz_len, 0 );

    /* Cutoff around 9 khz */
    /* A = conv(conv([8192,14613, 6868], [8192,12883, 7337]), [8192,11586, 7911]); */
    /* B = conv(conv([575, -948, 575], [575, -221, 575]), [575, 104, 575]); */
    SKP_Silk_biquad( samplesIn, SKP_Silk_SWB_detect_B_HP_Q13[ 0 ], SKP_Silk_SWB_detect_A_HP_Q13[ 0 ],
        psSWBdetect->S_HP_8_kHz[ 0 ], in_HP_8_kHz, HP_8_kHz_len );
    for( i = 1; i < NB_SOS; i++ ) {
        SKP_Silk_biquad( in_HP_8_kHz, SKP_Silk_SWB_detect_B_HP_Q13[ i ], SKP_Silk_SWB_detect_A_HP_Q13[ i ],
            psSWBdetect->S_HP_8_kHz[ i ], in_HP_8_kHz, HP_8_kHz_len );
    }

    /* Calculate energy in HP signal */
    SKP_Silk_sum_sqr_shift( &energy_32, &shift, in_HP_8_kHz, HP_8_kHz_len );

    /* Count concecutive samples above threshold, after adjusting threshold for number of input samples and shift */
    if( energy_32 > SKP_RSHIFT( SKP_SMULBB( HP_8_KHZ_THRES, HP_8_kHz_len ), shift ) ) {
        psSWBdetect->ConsecSmplsAboveThres += nSamplesIn;
        if( psSWBdetect->ConsecSmplsAboveThres > CONCEC_SWB_SMPLS_THRES ) {
            psSWBdetect->SWB_detected = 1;
        }
    } else {
        psSWBdetect->ConsecSmplsAboveThres -= nSamplesIn;
        psSWBdetect->ConsecSmplsAboveThres = SKP_max( psSWBdetect->ConsecSmplsAboveThres, 0 );
    }

    /* If sufficient speech activity and no SWB detected, we detect the signal as being WB */
    if( ( psSWBdetect->ActiveSpeech_ms > WB_DETECT_ACTIVE_SPEECH_MS_THRES ) && ( psSWBdetect->SWB_detected == 0 ) ) {
        psSWBdetect->WB_detected = 1;
    }
}