freeswitch/libs/silk/src/SKP_Silk_control_audio_bandwidth.c

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#include "SKP_Silk_main.h"

/* Control internal sampling rate */
SKP_int SKP_Silk_control_audio_bandwidth(
    SKP_Silk_encoder_state      *psEncC,            /* I/O  Pointer to Silk encoder state               */
    const SKP_int32             TargetRate_bps      /* I    Target max bitrate (bps)                    */
)
{
    SKP_int fs_kHz;

    fs_kHz = psEncC->fs_kHz;
    if( fs_kHz == 0 ) {
        /* Encoder has just been initialized */
        if( TargetRate_bps >= SWB2WB_BITRATE_BPS ) {
            fs_kHz = 24;
        } else if( TargetRate_bps >= WB2MB_BITRATE_BPS ) {
            fs_kHz = 16;
        } else if( TargetRate_bps >= MB2NB_BITRATE_BPS ) {
            fs_kHz = 12;
        } else {
            fs_kHz = 8;
        }
        /* Make sure internal rate is not higher than external rate or maximum allowed, or lower than minimum allowed */
        fs_kHz = SKP_min( fs_kHz, SKP_DIV32_16( psEncC->API_fs_Hz, 1000 ) );
        fs_kHz = SKP_min( fs_kHz, psEncC->maxInternal_fs_kHz );
    } else if( SKP_SMULBB( fs_kHz, 1000 ) > psEncC->API_fs_Hz || fs_kHz > psEncC->maxInternal_fs_kHz ) {
        /* Make sure internal rate is not higher than external rate or maximum allowed */
        fs_kHz = SKP_DIV32_16( psEncC->API_fs_Hz, 1000 );
        fs_kHz = SKP_min( fs_kHz, psEncC->maxInternal_fs_kHz );
    } else {
        /* State machine for the internal sampling rate switching */
        if( psEncC->API_fs_Hz > 8000 ) {
            /* Accumulate the difference between the target rate and limit for switching down */
            psEncC->bitrateDiff += SKP_MUL( psEncC->PacketSize_ms, psEncC->TargetRate_bps - psEncC->bitrate_threshold_down );
            psEncC->bitrateDiff  = SKP_min( psEncC->bitrateDiff, 0 );

            if( psEncC->vadFlag == NO_VOICE_ACTIVITY ) { /* Low speech activity */
                /* Check if we should switch down */
#if SWITCH_TRANSITION_FILTERING
                if( ( psEncC->sLP.transition_frame_no == 0 ) &&                         /* Transition phase not active */
                    ( psEncC->bitrateDiff <= -ACCUM_BITS_DIFF_THRESHOLD ||              /* Bitrate threshold is met */
                    ( psEncC->sSWBdetect.WB_detected * psEncC->fs_kHz == 24 ) ) ) {     /* Forced down-switching due to WB input */
                        psEncC->sLP.transition_frame_no = 1;                            /* Begin transition phase */
                        psEncC->sLP.mode                = 0;                            /* Switch down */
                } else if(
                    ( psEncC->sLP.transition_frame_no >= TRANSITION_FRAMES_DOWN ) &&    /* Transition phase complete */
                    ( psEncC->sLP.mode == 0 ) ) {                                       /* Ready to switch down */
                        psEncC->sLP.transition_frame_no = 0;                            /* Ready for new transition phase */
#else
                if( psEncC->bitrateDiff <= -ACCUM_BITS_DIFF_THRESHOLD ) {               /* Bitrate threshold is met */
#endif
                    psEncC->bitrateDiff = 0;

                    /* Switch to a lower sample frequency */
                    if( psEncC->fs_kHz == 24 ) {
                        fs_kHz = 16;
                    } else if( psEncC->fs_kHz == 16 ) {
                        fs_kHz = 12;
                    } else {
                        SKP_assert( psEncC->fs_kHz == 12 );
                        fs_kHz = 8;
                    }
                }

                /* Check if we should switch up */
                if( ( ( psEncC->fs_kHz * 1000 < psEncC->API_fs_Hz ) &&
                    ( psEncC->TargetRate_bps >= psEncC->bitrate_threshold_up ) &&
                    ( psEncC->sSWBdetect.WB_detected * psEncC->fs_kHz < 16 ) ) &&
                    ( ( ( psEncC->fs_kHz == 16 ) && ( psEncC->maxInternal_fs_kHz >= 24 ) ) ||
                    (   ( psEncC->fs_kHz == 12 ) && ( psEncC->maxInternal_fs_kHz >= 16 ) ) ||
                    (   ( psEncC->fs_kHz ==  8 ) && ( psEncC->maxInternal_fs_kHz >= 12 ) ) )
#if SWITCH_TRANSITION_FILTERING
                    && ( psEncC->sLP.transition_frame_no == 0 ) ) { /* No transition phase running, ready to switch */
                        psEncC->sLP.mode = 1; /* Switch up */
#else
                    ) {
#endif
                    psEncC->bitrateDiff = 0;

                    /* Switch to a higher sample frequency */
                    if( psEncC->fs_kHz == 8 ) {
                        fs_kHz = 12;
                    } else if( psEncC->fs_kHz == 12 ) {
                        fs_kHz = 16;
                    } else {
                        SKP_assert( psEncC->fs_kHz == 16 );
                        fs_kHz = 24;
                    }
                }
            }
        }

#if SWITCH_TRANSITION_FILTERING
        /* After switching up, stop transition filter during speech inactivity */
        if( ( psEncC->sLP.mode == 1 ) &&
            ( psEncC->sLP.transition_frame_no >= TRANSITION_FRAMES_UP ) &&
            ( psEncC->vadFlag == NO_VOICE_ACTIVITY ) ) {

                psEncC->sLP.transition_frame_no = 0;

                /* Reset transition filter state */
                SKP_memset( psEncC->sLP.In_LP_State, 0, 2 * sizeof( SKP_int32 ) );
        }
#endif
    }



    return fs_kHz;
}