ref: c43b1bc8c0a55dde4b7b33cf3f6eba9595ecdd99
dir: /silk/control_SNR.c/
/***********************************************************************
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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "main.h"
#include "tuning_parameters.h"
/* Control SNR of redidual quantizer */
opus_int silk_control_SNR(
silk_encoder_state *psEncC, /* I/O Pointer to Silk encoder state */
opus_int32 TargetRate_bps /* I Target max bitrate (bps) */
)
{
opus_int k, ret = SILK_NO_ERROR;
opus_int32 frac_Q6;
const opus_int32 *rateTable;
/* Set bitrate/coding quality */
TargetRate_bps = silk_LIMIT( TargetRate_bps, MIN_TARGET_RATE_BPS, MAX_TARGET_RATE_BPS );
if( TargetRate_bps != psEncC->TargetRate_bps ) {
psEncC->TargetRate_bps = TargetRate_bps;
/* If new TargetRate_bps, translate to SNR_dB value */
if( psEncC->fs_kHz == 8 ) {
rateTable = silk_TargetRate_table_NB;
} else if( psEncC->fs_kHz == 12 ) {
rateTable = silk_TargetRate_table_MB;
} else {
rateTable = silk_TargetRate_table_WB;
}
/* Reduce bitrate for 10 ms modes in these calculations */
if( psEncC->nb_subfr == 2 ) {
TargetRate_bps -= REDUCE_BITRATE_10_MS_BPS;
}
/* Find bitrate interval in table and interpolate */
for( k = 1; k < TARGET_RATE_TAB_SZ; k++ ) {
if( TargetRate_bps <= rateTable[ k ] ) {
frac_Q6 = silk_DIV32( silk_LSHIFT( TargetRate_bps - rateTable[ k - 1 ], 6 ),
rateTable[ k ] - rateTable[ k - 1 ] );
psEncC->SNR_dB_Q7 = silk_LSHIFT( silk_SNR_table_Q1[ k - 1 ], 6 ) + silk_MUL( frac_Q6, silk_SNR_table_Q1[ k ] - silk_SNR_table_Q1[ k - 1 ] );
break;
}
}
}
return ret;
}