Commit 13ece611 authored by Vladimir Malenovsky's avatar Vladimir Malenovsky
Browse files

add a comment explaining the 1/length contant

parent 5edea136

lib_enc/ivas_stereo_ica_enc_fx.c

+2 −18
Original line number Diff line number Diff line
@@ -2220,13 +2220,7 @@ static void unclr_calc_corr_features_fx( 
    Word16 *corrEst_ncorr_exp )

{

    Word16 i, corrLagMax, d_corrLagMax, tempLen, k;

#ifdef FIX_NONBE_2580_USE_LENGTH_NOT_CONSTANT

    Word16 inv_len_exp;

#endif

    Word32 num, den;

#ifdef FIX_NONBE_2580_USE_LENGTH_NOT_CONSTANT

    Word32 inv_len;

#endif

    Word32 corrL, corrR, ener, ener_side, mono_i, side_i, ic_Lm, ic_Rm, tdm_es_em, m_corrL_corrR, d_corrL_corrR;

    Word32 sum_prod, corrEstMax;

    Word16 corrL_exp, corrR_exp, ener_exp, ener_side_exp, sum_prod_exp, exp, exp1, exp2, num_exp, den_exp;
@@ -2275,17 +2269,8 @@ static void unclr_calc_corr_features_fx( 


    /* average energy of L and R channels */

#ifdef FIX_NONBE_2580_USE_LENGTH_NOT_CONSTANT

    inv_len = BASOP_Util_Divide3232_Scale_newton( ONE_IN_Q31, L_deposit_l( length ), &inv_len_exp ); /* Q31-inv_len_exp */



    hStereoClassif->ave_ener_L_fx = Mpy_32_32( hStereoTCA->E1_mem_fx, inv_len ); /* Q31-hStereoClassif->ave_ener_L_fx_e */

    move32();

    hStereoClassif->ave_ener_L_fx_e = add( hStereoTCA->E1_mem_exp, inv_len_exp );

    move16();

    hStereoClassif->ave_ener_R_fx = Mpy_32_32( hStereoTCA->E2_mem_fx, inv_len ); /* Q31-hStereoClassif->ave_ener_R_fx_e */

    move32();

    hStereoClassif->ave_ener_R_fx_e = add( hStereoTCA->E2_mem_exp, inv_len_exp );

    move16();

#else

    /* Note, that length is a fixed value equal to L_FRAME_DS, so 1/length = 1/160 = 13421772 */

#endif

    hStereoClassif->ave_ener_L_fx = Mpy_32_32( hStereoTCA->E1_mem_fx, 13421772 /* 1/length in Q31*/ ); /* Q31-hStereoClassif->ave_ener_L_fx_e */

    move32();

    hStereoClassif->ave_ener_L_fx_e = hStereoTCA->E1_mem_exp;
@@ -2294,7 +2279,6 @@ static void unclr_calc_corr_features_fx( 
    move32();

    hStereoClassif->ave_ener_R_fx_e = hStereoTCA->E2_mem_exp;

    move16();

#endif



    /* unnormalized L/R correlation */

    IF( sum_prod )