ref: d3358b1d42f5092c42f45a68f1e53a16b5a6926f
dir: /silk/silk_resampler.c/
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/* Matrix of resampling methods used:
* Fs_out (kHz)
* 8 12 16 24 32 44.1 48
*
* 8 C UF U UF UF UF UF
* 12 AF C UF U UF UF UF
* 16 D AF C UF U UF UF
* Fs_in (kHz) 24 AIF D AF C UF UF U
* 32 UF AF D AF C UF UF
* 44.1 AMI AMI AMI AMI AMI C UF
* 48 DAF DAF AF D AF UF C
*
* default method: UF
*
* C -> Copy (no resampling)
* D -> Allpass-based 2x downsampling
* U -> Allpass-based 2x upsampling
* DAF -> Allpass-based 2x downsampling followed by AR2 filter followed by FIR interpolation
* UF -> Allpass-based 2x upsampling followed by FIR interpolation
* AMI -> ARMA4 filter followed by FIR interpolation
* AF -> AR2 filter followed by FIR interpolation
*
* Input signals sampled above 48 kHz are first downsampled to at most 48 kHz.
* Output signals sampled above 48 kHz are upsampled from at most 48 kHz.
*/
#include "silk_resampler_private.h"
/* Greatest common divisor */
static SKP_int32 gcd(
SKP_int32 a,
SKP_int32 b
)
{
SKP_int32 tmp;
while( b > 0 ) {
tmp = a - b * SKP_DIV32( a, b );
a = b;
b = tmp;
}
return a;
}
/* Initialize/reset the resampler state for a given pair of input/output sampling rates */
SKP_int silk_resampler_init(
silk_resampler_state_struct *S, /* I/O: Resampler state */
SKP_int32 Fs_Hz_in, /* I: Input sampling rate (Hz) */
SKP_int32 Fs_Hz_out /* I: Output sampling rate (Hz) */
)
{
SKP_int32 cycleLen, cyclesPerBatch, up2 = 0, down2 = 0;
/* Clear state */
SKP_memset( S, 0, sizeof( silk_resampler_state_struct ) );
/* Input checking */
#if RESAMPLER_SUPPORT_ABOVE_48KHZ
if( Fs_Hz_in < 8000 || Fs_Hz_in > 192000 || Fs_Hz_out < 8000 || Fs_Hz_out > 192000 ) {
#else
if( Fs_Hz_in < 8000 || Fs_Hz_in > 48000 || Fs_Hz_out < 8000 || Fs_Hz_out > 48000 ) {
#endif
SKP_assert( 0 );
return -1;
}
#if RESAMPLER_SUPPORT_ABOVE_48KHZ
/* Determine pre downsampling and post upsampling */
if( Fs_Hz_in > 96000 ) {
S->nPreDownsamplers = 2;
S->down_pre_function = silk_resampler_private_down4;
} else if( Fs_Hz_in > 48000 ) {
S->nPreDownsamplers = 1;
S->down_pre_function = silk_resampler_down2;
} else {
S->nPreDownsamplers = 0;
S->down_pre_function = NULL;
}
if( Fs_Hz_out > 96000 ) {
S->nPostUpsamplers = 2;
S->up_post_function = silk_resampler_private_up4;
} else if( Fs_Hz_out > 48000 ) {
S->nPostUpsamplers = 1;
S->up_post_function = silk_resampler_up2;
} else {
S->nPostUpsamplers = 0;
S->up_post_function = NULL;
}
if( S->nPreDownsamplers + S->nPostUpsamplers > 0 ) {
/* Ratio of output/input samples */
S->ratio_Q16 = SKP_LSHIFT32( SKP_DIV32( SKP_LSHIFT32( Fs_Hz_out, 13 ), Fs_Hz_in ), 3 );
/* Make sure the ratio is rounded up */
while( SKP_SMULWW( S->ratio_Q16, Fs_Hz_in ) < Fs_Hz_out ) S->ratio_Q16++;
/* Batch size is 10 ms */
S->batchSizePrePost = SKP_DIV32_16( Fs_Hz_in, 100 );
/* Convert sampling rate to those after pre-downsampling and before post-upsampling */
Fs_Hz_in = SKP_RSHIFT( Fs_Hz_in, S->nPreDownsamplers );
Fs_Hz_out = SKP_RSHIFT( Fs_Hz_out, S->nPostUpsamplers );
}
#endif
/* Number of samples processed per batch */
/* First, try 10 ms frames */
S->batchSize = SKP_DIV32_16( Fs_Hz_in, 100 );
if( ( SKP_MUL( S->batchSize, 100 ) != Fs_Hz_in ) || ( Fs_Hz_in % 100 != 0 ) ) {
/* No integer number of input or output samples with 10 ms frames, use greatest common divisor */
cycleLen = SKP_DIV32( Fs_Hz_in, gcd( Fs_Hz_in, Fs_Hz_out ) );
cyclesPerBatch = SKP_DIV32( RESAMPLER_MAX_BATCH_SIZE_IN, cycleLen );
if( cyclesPerBatch == 0 ) {
/* cycleLen too big, let's just use the maximum batch size. Some distortion will result. */
S->batchSize = RESAMPLER_MAX_BATCH_SIZE_IN;
SKP_assert( 0 );
} else {
S->batchSize = SKP_MUL( cyclesPerBatch, cycleLen );
}
}
/* Find resampler with the right sampling ratio */
if( Fs_Hz_out > Fs_Hz_in ) {
/* Upsample */
if( Fs_Hz_out == SKP_MUL( Fs_Hz_in, 2 ) ) { /* Fs_out : Fs_in = 2 : 1 */
/* Special case: directly use 2x upsampler */
S->resampler_function = silk_resampler_private_up2_HQ_wrapper;
} else {
/* Default resampler */
S->resampler_function = silk_resampler_private_IIR_FIR;
up2 = 1;
if( Fs_Hz_in > 24000 ) {
/* Low-quality all-pass upsampler */
S->up2_function = silk_resampler_up2;
} else {
/* High-quality all-pass upsampler */
S->up2_function = silk_resampler_private_up2_HQ;
}
}
} else if ( Fs_Hz_out < Fs_Hz_in ) {
/* Downsample */
if( SKP_MUL( Fs_Hz_out, 4 ) == SKP_MUL( Fs_Hz_in, 3 ) ) { /* Fs_out : Fs_in = 3 : 4 */
S->FIR_Fracs = 3;
S->Coefs = silk_Resampler_3_4_COEFS;
S->resampler_function = silk_resampler_private_down_FIR;
} else if( SKP_MUL( Fs_Hz_out, 3 ) == SKP_MUL( Fs_Hz_in, 2 ) ) { /* Fs_out : Fs_in = 2 : 3 */
S->FIR_Fracs = 2;
S->Coefs = silk_Resampler_2_3_COEFS;
S->resampler_function = silk_resampler_private_down_FIR;
} else if( SKP_MUL( Fs_Hz_out, 2 ) == Fs_Hz_in ) { /* Fs_out : Fs_in = 1 : 2 */
S->FIR_Fracs = 1;
S->Coefs = silk_Resampler_1_2_COEFS;
S->resampler_function = silk_resampler_private_down_FIR;
} else if( SKP_MUL( Fs_Hz_out, 8 ) == SKP_MUL( Fs_Hz_in, 3 ) ) { /* Fs_out : Fs_in = 3 : 8 */
S->FIR_Fracs = 3;
S->Coefs = silk_Resampler_3_8_COEFS;
S->resampler_function = silk_resampler_private_down_FIR;
} else if( SKP_MUL( Fs_Hz_out, 3 ) == Fs_Hz_in ) { /* Fs_out : Fs_in = 1 : 3 */
S->FIR_Fracs = 1;
S->Coefs = silk_Resampler_1_3_COEFS;
S->resampler_function = silk_resampler_private_down_FIR;
} else if( SKP_MUL( Fs_Hz_out, 4 ) == Fs_Hz_in ) { /* Fs_out : Fs_in = 1 : 4 */
S->FIR_Fracs = 1;
down2 = 1;
S->Coefs = silk_Resampler_1_2_COEFS;
S->resampler_function = silk_resampler_private_down_FIR;
} else if( SKP_MUL( Fs_Hz_out, 6 ) == Fs_Hz_in ) { /* Fs_out : Fs_in = 1 : 6 */
S->FIR_Fracs = 1;
down2 = 1;
S->Coefs = silk_Resampler_1_3_COEFS;
S->resampler_function = silk_resampler_private_down_FIR;
} else if( SKP_MUL( Fs_Hz_out, 441 ) == SKP_MUL( Fs_Hz_in, 80 ) ) { /* Fs_out : Fs_in = 80 : 441 */
S->Coefs = silk_Resampler_80_441_ARMA4_COEFS;
S->resampler_function = silk_resampler_private_IIR_FIR;
} else if( SKP_MUL( Fs_Hz_out, 441 ) == SKP_MUL( Fs_Hz_in, 120 ) ) { /* Fs_out : Fs_in = 120 : 441 */
S->Coefs = silk_Resampler_120_441_ARMA4_COEFS;
S->resampler_function = silk_resampler_private_IIR_FIR;
} else if( SKP_MUL( Fs_Hz_out, 441 ) == SKP_MUL( Fs_Hz_in, 160 ) ) { /* Fs_out : Fs_in = 160 : 441 */
S->Coefs = silk_Resampler_160_441_ARMA4_COEFS;
S->resampler_function = silk_resampler_private_IIR_FIR;
} else if( SKP_MUL( Fs_Hz_out, 441 ) == SKP_MUL( Fs_Hz_in, 240 ) ) { /* Fs_out : Fs_in = 240 : 441 */
S->Coefs = silk_Resampler_240_441_ARMA4_COEFS;
S->resampler_function = silk_resampler_private_IIR_FIR;
} else if( SKP_MUL( Fs_Hz_out, 441 ) == SKP_MUL( Fs_Hz_in, 320 ) ) { /* Fs_out : Fs_in = 320 : 441 */
S->Coefs = silk_Resampler_320_441_ARMA4_COEFS;
S->resampler_function = silk_resampler_private_IIR_FIR;
} else {
/* Default resampler */
S->resampler_function = silk_resampler_private_IIR_FIR;
up2 = 1;
if( Fs_Hz_in > 24000 ) {
/* Low-quality all-pass upsampler */
S->up2_function = silk_resampler_up2;
} else {
/* High-quality all-pass upsampler */
S->up2_function = silk_resampler_private_up2_HQ;
}
}
} else {
/* Input and output sampling rates are equal: copy */
S->resampler_function = silk_resampler_private_copy;
}
S->input2x = up2 | down2;
/* Ratio of input/output samples */
S->invRatio_Q16 = SKP_LSHIFT32( SKP_DIV32( SKP_LSHIFT32( Fs_Hz_in, 14 + up2 - down2 ), Fs_Hz_out ), 2 );
/* Make sure the ratio is rounded up */
while( SKP_SMULWW( S->invRatio_Q16, SKP_LSHIFT32( Fs_Hz_out, down2 ) ) < SKP_LSHIFT32( Fs_Hz_in, up2 ) ) {
S->invRatio_Q16++;
}
S->magic_number = 123456789;
return 0;
}
/* Clear the states of all resampling filters, without resetting sampling rate ratio */
SKP_int silk_resampler_clear(
silk_resampler_state_struct *S /* I/O: Resampler state */
)
{
/* Clear state */
SKP_memset( S->sDown2, 0, sizeof( S->sDown2 ) );
SKP_memset( S->sIIR, 0, sizeof( S->sIIR ) );
SKP_memset( S->sFIR, 0, sizeof( S->sFIR ) );
#if RESAMPLER_SUPPORT_ABOVE_48KHZ
SKP_memset( S->sDownPre, 0, sizeof( S->sDownPre ) );
SKP_memset( S->sUpPost, 0, sizeof( S->sUpPost ) );
#endif
return 0;
}
/* Resampler: convert from one sampling rate to another */
SKP_int silk_resampler(
silk_resampler_state_struct *S, /* I/O: Resampler state */
SKP_int16 out[], /* O: Output signal */
const SKP_int16 in[], /* I: Input signal */
SKP_int32 inLen /* I: Number of input samples */
)
{
/* Verify that state was initialized and has not been corrupted */
if( S->magic_number != 123456789 ) {
SKP_assert( 0 );
return -1;
}
#if RESAMPLER_SUPPORT_ABOVE_48KHZ
if( S->nPreDownsamplers + S->nPostUpsamplers > 0 ) {
/* The input and/or output sampling rate is above 48000 Hz */
SKP_int32 nSamplesIn, nSamplesOut;
SKP_int16 in_buf[ 480 ], out_buf[ 480 ];
while( inLen > 0 ) {
/* Number of input and output samples to process */
nSamplesIn = SKP_min( inLen, S->batchSizePrePost );
nSamplesOut = SKP_SMULWB( S->ratio_Q16, nSamplesIn );
SKP_assert( SKP_RSHIFT32( nSamplesIn, S->nPreDownsamplers ) <= 480 );
SKP_assert( SKP_RSHIFT32( nSamplesOut, S->nPostUpsamplers ) <= 480 );
if( S->nPreDownsamplers > 0 ) {
S->down_pre_function( S->sDownPre, in_buf, in, nSamplesIn );
if( S->nPostUpsamplers > 0 ) {
S->resampler_function( S, out_buf, in_buf, SKP_RSHIFT32( nSamplesIn, S->nPreDownsamplers ) );
S->up_post_function( S->sUpPost, out, out_buf, SKP_RSHIFT32( nSamplesOut, S->nPostUpsamplers ) );
} else {
S->resampler_function( S, out, in_buf, SKP_RSHIFT32( nSamplesIn, S->nPreDownsamplers ) );
}
} else {
S->resampler_function( S, out_buf, in, SKP_RSHIFT32( nSamplesIn, S->nPreDownsamplers ) );
S->up_post_function( S->sUpPost, out, out_buf, SKP_RSHIFT32( nSamplesOut, S->nPostUpsamplers ) );
}
in += nSamplesIn;
out += nSamplesOut;
inLen -= nSamplesIn;
}
} else
#endif
{
/* Input and output sampling rate are at most 48000 Hz */
S->resampler_function( S, out, in, inLen );
}
return 0;
}