Commit ad0a24c3 authored by vaillancour's avatar vaillancour
Browse files

more comments inside stereo_tdm_ener_analysis()

parent 8a69cf17

lib_enc/ivas_stereo_td_analysis.c

+35 −4
Original line number Diff line number Diff line
@@ -194,8 +194,11 @@ int16_t stereo_tdm_ener_analysis( 
    hStereoTD->prev_fr_LRTD_TD_dec = hCPE->hStereoClassif->lrtd_mode;



    /*----------------------------------------------------------------*

     * When the energies of channels are low enough, compute the ratio

     * of L and R needed to create new mono/side signals

     * If the ivas format is MASA_ISM and the signal is classified 

     * as having a low correlation (interfering talker or uncorrelated content)

     * and the bitrate available is lower than 15 kbps.

     * then, then next frame will be encoded using the normal TD, which allows 

     * for a lower total bitrate

     *----------------------------------------------------------------*/



    if ( ivas_format == MASA_ISM_FORMAT )
@@ -206,6 +209,19 @@ int16_t stereo_tdm_ener_analysis( 
            hStereoTD->prev_fr_LRTD_TD_dec = 0;

        }

    }

    /*----------------------------------------------------------------*

     * An rms energy threshold is set and will be use later to decide when 

     * it is the right time to change the mixing level or to change primary 

     * and secondary channel.

     * 

     * If the signal is classified as having a low correlation 

     * (interfering talker or uncorrelated content), 

     * then, the rms threshold is lowered and further more if the long 

     * term rms energy of at least one of the channel is <= 75. On the other hand, 

     * if the lt term rms of both channel is above that threshold but the 

     * coding mode of both channel is considered as inactive, then the 

     * rms threshold is increased.

     *----------------------------------------------------------------*/



    rms_thd = RMS_MIN;

    if ( hCPE->hStereoClassif->lrtd_mode == 1 )
@@ -219,8 +235,23 @@ int16_t stereo_tdm_ener_analysis( 
        {

            rms_thd /= .2f;

        }



        /* Overwrite the LR decision flag in case the signals is already considered as S/M or when the signal is very similar between left and right channel */

       /*----------------------------------------------------------------*

        * Overwrite the LRTD decision flag and use the normal TD for the 

        * following cases:

        *1- The signals is already considered as S/M 

        *2- The LRTD flag is set to 1 and the last switching frame 

        *   happened more than 10 frames ago and both channel are considered 

        *   as inactive or the uncorrelated decision flag is 0 (not completely uncorrelated) 

        *   and the interfering talker score and the weighted interfering score 

        *   are low or the uncorrelated decision flag is 1 (likely uncorrelated) and 

        *   both channel are classified as unvoiced and the uncorrelated score is low

        *3- The LRTD flag is set to 0 and both channel are considered 

        *   as inactive or the uncorrelated decision flag is 0 (not completely uncorrelated) 

        *   and the interfering talker score and the weighted interfering score 

        *   are low or the uncorrelated decision flag is 1 (likely uncorrelated) and 

        *   both channel are classified as unvoiced and the uncorrelated score is low

        * the conditions 2 and 3 vary slightly to ensure an hysteresis effect

        *----------------------------------------------------------------*/

        if ( tdm_SM_flag_loc == 1 )

        {

            hStereoTD->prev_fr_LRTD_TD_dec = 0;