text: /***************************************************************************
  Copyright (c) 2006-2011, Skype Limited. All rights reserved.
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  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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  ***************************************************************************/
  
  #ifdef HAVE_CONFIG_H
  #include "config.h"
  #endif
  #ifdef FIXED_POINT
  #include "main_FIX.h"
  #else
  #include "main_FLP.h"
  #endif
  #include "tuning_parameters.h"
  
  /* High-pass filter with cutoff frequency adaptation based on pitch lag statistics */
  void silk_HP_variable_cutoff(
      silk_encoder_state_Fxx          state_Fxx[]                         /* I/O  Encoder states                              */
  )
  {
     opus_int   quality_Q15;
     opus_int32 pitch_freq_Hz_Q16, pitch_freq_log_Q7, delta_freq_Q7;
     silk_encoder_state *psEncC1 = &state_Fxx[ 0 ].sCmn;
  
     /* Adaptive cutoff frequency: estimate low end of pitch frequency range */
     if( psEncC1->prevSignalType == TYPE_VOICED ) {
        /* difference, in log domain */
        pitch_freq_Hz_Q16 = silk_DIV32_16( silk_LSHIFT( silk_MUL( psEncC1->fs_kHz, 1000 ), 16 ), psEncC1->prevLag );
        pitch_freq_log_Q7 = silk_lin2log( pitch_freq_Hz_Q16 ) - ( 16 << 7 );
  
        /* adjustment based on quality */
        quality_Q15 = psEncC1->input_quality_bands_Q15[ 0 ];
        pitch_freq_log_Q7 = silk_SMLAWB( pitch_freq_log_Q7, silk_SMULWB( silk_LSHIFT( -quality_Q15, 2 ), quality_Q15 ),
              pitch_freq_log_Q7 - ( silk_lin2log( SILK_FIX_CONST( VARIABLE_HP_MIN_CUTOFF_HZ, 16 ) ) - ( 16 << 7 ) ) );
  
        /* delta_freq = pitch_freq_log - psEnc->variable_HP_smth1; */
        delta_freq_Q7 = pitch_freq_log_Q7 - silk_RSHIFT( psEncC1->variable_HP_smth1_Q15, 8 );
        if( delta_freq_Q7 < 0 ) {
           /* less smoothing for decreasing pitch frequency, to track something close to the minimum */
           delta_freq_Q7 = silk_MUL( delta_freq_Q7, 3 );
        }
  
        /* limit delta, to reduce impact of outliers in pitch estimation */
        delta_freq_Q7 = silk_LIMIT_32( delta_freq_Q7, -SILK_FIX_CONST( VARIABLE_HP_MAX_DELTA_FREQ, 7 ), SILK_FIX_CONST( VARIABLE_HP_MAX_DELTA_FREQ, 7 ) );
  
        /* update smoother */
        psEncC1->variable_HP_smth1_Q15 = silk_SMLAWB( psEncC1->variable_HP_smth1_Q15,
              silk_SMULBB( psEncC1->speech_activity_Q8, delta_freq_Q7 ), SILK_FIX_CONST( VARIABLE_HP_SMTH_COEF1, 16 ) );
  
        /* limit frequency range */
        psEncC1->variable_HP_smth1_Q15 = silk_LIMIT_32( psEncC1->variable_HP_smth1_Q15,
              silk_LSHIFT( silk_lin2log( VARIABLE_HP_MIN_CUTOFF_HZ ), 8 ),
              silk_LSHIFT( silk_lin2log( VARIABLE_HP_MAX_CUTOFF_HZ ), 8 ) );
     }
  }
  