ref: cc3405045567b70e816e91e9f130b8d8fff36d19
dir: /silk/resampler_private_up4.c/
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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "SigProc_FIX.h"
#include "resampler_private.h"
/* Upsample by a factor 4, Note: low quality, only use with output sampling rates above 96 kHz. */
void silk_resampler_private_up4(
opus_int32 *S, /* I/O: State vector [ 2 ] */
opus_int16 *out, /* O: Output signal [ 4 * len ] */
const opus_int16 *in, /* I: Input signal [ len ] */
opus_int32 len /* I: Number of INPUT samples */
)
{
opus_int32 k;
opus_int32 in32, out32, Y, X;
opus_int16 out16;
silk_assert( silk_resampler_up2_lq_0 > 0 );
silk_assert( silk_resampler_up2_lq_1 < 0 );
/* Internal variables and state are in Q10 format */
for( k = 0; k < len; k++ ) {
/* Convert to Q10 */
in32 = silk_LSHIFT( (opus_int32)in[ k ], 10 );
/* All-pass section for even output sample */
Y = silk_SUB32( in32, S[ 0 ] );
X = silk_SMULWB( Y, silk_resampler_up2_lq_0 );
out32 = silk_ADD32( S[ 0 ], X );
S[ 0 ] = silk_ADD32( in32, X );
/* Convert back to int16 and store to output */
out16 = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( out32, 10 ) );
out[ 4 * k ] = out16;
out[ 4 * k + 1 ] = out16;
/* All-pass section for odd output sample */
Y = silk_SUB32( in32, S[ 1 ] );
X = silk_SMLAWB( Y, Y, silk_resampler_up2_lq_1 );
out32 = silk_ADD32( S[ 1 ], X );
S[ 1 ] = silk_ADD32( in32, X );
/* Convert back to int16 and store to output */
out16 = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( out32, 10 ) );
out[ 4 * k + 2 ] = out16;
out[ 4 * k + 3 ] = out16;
}
}