ref: ad15ed840bb0b178f9f7c31c6c7298078ff4af94
dir: /silk/silk_resampler_down2_3.c/
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#include "silk_SigProc_FIX.h"
#include "silk_resampler_private.h"
#define ORDER_FIR 4
/* Downsample by a factor 2/3, low quality */
void silk_resampler_down2_3(
opus_int32 *S, /* I/O: State vector [ 6 ] */
opus_int16 *out, /* O: Output signal [ floor(2*inLen/3) ] */
const opus_int16 *in, /* I: Input signal [ inLen ] */
opus_int32 inLen /* I: Number of input samples */
)
{
opus_int32 nSamplesIn, counter, res_Q6;
opus_int32 buf[ RESAMPLER_MAX_BATCH_SIZE_IN + ORDER_FIR ];
opus_int32 *buf_ptr;
/* Copy buffered samples to start of buffer */
SKP_memcpy( buf, S, ORDER_FIR * sizeof( opus_int32 ) );
/* Iterate over blocks of frameSizeIn input samples */
while( 1 ) {
nSamplesIn = SKP_min( inLen, RESAMPLER_MAX_BATCH_SIZE_IN );
/* Second-order AR filter (output in Q8) */
silk_resampler_private_AR2( &S[ ORDER_FIR ], &buf[ ORDER_FIR ], in,
silk_Resampler_2_3_COEFS_LQ, nSamplesIn );
/* Interpolate filtered signal */
buf_ptr = buf;
counter = nSamplesIn;
while( counter > 2 ) {
/* Inner product */
res_Q6 = SKP_SMULWB( buf_ptr[ 0 ], silk_Resampler_2_3_COEFS_LQ[ 2 ] );
res_Q6 = SKP_SMLAWB( res_Q6, buf_ptr[ 1 ], silk_Resampler_2_3_COEFS_LQ[ 3 ] );
res_Q6 = SKP_SMLAWB( res_Q6, buf_ptr[ 2 ], silk_Resampler_2_3_COEFS_LQ[ 5 ] );
res_Q6 = SKP_SMLAWB( res_Q6, buf_ptr[ 3 ], silk_Resampler_2_3_COEFS_LQ[ 4 ] );
/* Scale down, saturate and store in output array */
*out++ = (opus_int16)SKP_SAT16( SKP_RSHIFT_ROUND( res_Q6, 6 ) );
res_Q6 = SKP_SMULWB( buf_ptr[ 1 ], silk_Resampler_2_3_COEFS_LQ[ 4 ] );
res_Q6 = SKP_SMLAWB( res_Q6, buf_ptr[ 2 ], silk_Resampler_2_3_COEFS_LQ[ 5 ] );
res_Q6 = SKP_SMLAWB( res_Q6, buf_ptr[ 3 ], silk_Resampler_2_3_COEFS_LQ[ 3 ] );
res_Q6 = SKP_SMLAWB( res_Q6, buf_ptr[ 4 ], silk_Resampler_2_3_COEFS_LQ[ 2 ] );
/* Scale down, saturate and store in output array */
*out++ = (opus_int16)SKP_SAT16( SKP_RSHIFT_ROUND( res_Q6, 6 ) );
buf_ptr += 3;
counter -= 3;
}
in += nSamplesIn;
inLen -= nSamplesIn;
if( inLen > 0 ) {
/* More iterations to do; copy last part of filtered signal to beginning of buffer */
SKP_memcpy( buf, &buf[ nSamplesIn ], ORDER_FIR * sizeof( opus_int32 ) );
} else {
break;
}
}
/* Copy last part of filtered signal to the state for the next call */
SKP_memcpy( S, &buf[ nSamplesIn ], ORDER_FIR * sizeof( opus_int32 ) );
}