opus/silk/resampler.c

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Copyright (c) 2006-2012 IETF Trust and Skype Limited. All rights reserved.

This file is extracted from RFC6716. Please see that RFC for additional
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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

/*
 * Matrix of resampling methods used:
 *                                 Fs_out (kHz)
 *                        8      12     16     24     48
 *
 *               8        C      UF     U      UF     UF
 *              12        AF     C      UF     U      UF
 * Fs_in (kHz)  16        D      AF     C      UF     UF
 *              24        AF     D      AF     C      U
 *              48        AF     AF     AF     D      C
 *
 * C   -> Copy (no resampling)
 * D   -> Allpass-based 2x downsampling
 * U   -> Allpass-based 2x upsampling
 * UF  -> Allpass-based 2x upsampling followed by FIR interpolation
 * AF  -> AR2 filter followed by FIR interpolation
 */

#include "resampler_private.h"

/* Tables with delay compensation values to equalize total delay for different modes */
static const opus_int8 delay_matrix_enc[ 5 ][ 3 ] = {
/* in  \ out  8  12  16 */
/*  8 */   {  6,  0,  3 },
/* 12 */   {  0,  7,  3 },
/* 16 */   {  0,  1, 10 },
/* 24 */   {  0,  2,  6 },
/* 48 */   { 18, 10, 12 }
};

static const opus_int8 delay_matrix_dec[ 3 ][ 5 ] = {
/* in  \ out  8  12  16  24  48 */
/*  8 */   {  4,  0,  2,  0,  0 },
/* 12 */   {  0,  9,  4,  7,  4 },
/* 16 */   {  0,  3, 12,  7,  7 }
};

/* Simple way to make [8000, 12000, 16000, 24000, 48000] to [0, 1, 2, 3, 4] */
#define rateID(R) ( ( ( ((R)>>12) - ((R)>16000) ) >> ((R)>24000) ) - 1 )

#define USE_silk_resampler_copy                     (0)
#define USE_silk_resampler_private_up2_HQ_wrapper   (1)
#define USE_silk_resampler_private_IIR_FIR          (2)
#define USE_silk_resampler_private_down_FIR         (3)

/* Initialize/reset the resampler state for a given pair of input/output sampling rates */
opus_int silk_resampler_init(
    silk_resampler_state_struct *S,                 /* I/O  Resampler state                                             */
    opus_int32                  Fs_Hz_in,           /* I    Input sampling rate (Hz)                                    */
    opus_int32                  Fs_Hz_out,          /* I    Output sampling rate (Hz)                                   */
    opus_int                    forEnc              /* I    If 1: encoder; if 0: decoder                                */
)
{
    opus_int up2x;

    /* Clear state */
    silk_memset( S, 0, sizeof( silk_resampler_state_struct ) );

    /* Input checking */
    if( forEnc ) {
        if( ( Fs_Hz_in  != 8000 && Fs_Hz_in  != 12000 && Fs_Hz_in  != 16000 && Fs_Hz_in  != 24000 && Fs_Hz_in  != 48000 ) ||
            ( Fs_Hz_out != 8000 && Fs_Hz_out != 12000 && Fs_Hz_out != 16000 ) ) {
            silk_assert( 0 );
            return -1;
        }
        S->inputDelay = delay_matrix_enc[ rateID( Fs_Hz_in ) ][ rateID( Fs_Hz_out ) ];
    } else {
        if( ( Fs_Hz_in  != 8000 && Fs_Hz_in  != 12000 && Fs_Hz_in  != 16000 ) ||
            ( Fs_Hz_out != 8000 && Fs_Hz_out != 12000 && Fs_Hz_out != 16000 && Fs_Hz_out != 24000 && Fs_Hz_out != 48000 ) ) {
            silk_assert( 0 );
            return -1;
        }
        S->inputDelay = delay_matrix_dec[ rateID( Fs_Hz_in ) ][ rateID( Fs_Hz_out ) ];
    }

    S->Fs_in_kHz  = silk_DIV32_16( Fs_Hz_in,  1000 );
    S->Fs_out_kHz = silk_DIV32_16( Fs_Hz_out, 1000 );

    /* Number of samples processed per batch */
    S->batchSize = S->Fs_in_kHz * RESAMPLER_MAX_BATCH_SIZE_MS;

    /* Find resampler with the right sampling ratio */
    up2x = 0;
    if( Fs_Hz_out > Fs_Hz_in ) {
        /* Upsample */
        if( Fs_Hz_out == silk_MUL( Fs_Hz_in, 2 ) ) {                            /* Fs_out : Fs_in = 2 : 1 */
            /* Special case: directly use 2x upsampler */
            S->resampler_function = USE_silk_resampler_private_up2_HQ_wrapper;
        } else {
            /* Default resampler */
            S->resampler_function = USE_silk_resampler_private_IIR_FIR;
            up2x = 1;
        }
    } else if ( Fs_Hz_out < Fs_Hz_in ) {
        /* Downsample */
         S->resampler_function = USE_silk_resampler_private_down_FIR;
        if( silk_MUL( Fs_Hz_out, 4 ) == silk_MUL( Fs_Hz_in, 3 ) ) {             /* Fs_out : Fs_in = 3 : 4 */
            S->FIR_Fracs = 3;
            S->FIR_Order = RESAMPLER_DOWN_ORDER_FIR0;
            S->Coefs = silk_Resampler_3_4_COEFS;
        } else if( silk_MUL( Fs_Hz_out, 3 ) == silk_MUL( Fs_Hz_in, 2 ) ) {      /* Fs_out : Fs_in = 2 : 3 */
            S->FIR_Fracs = 2;
            S->FIR_Order = RESAMPLER_DOWN_ORDER_FIR0;
            S->Coefs = silk_Resampler_2_3_COEFS;
        } else if( silk_MUL( Fs_Hz_out, 2 ) == Fs_Hz_in ) {                     /* Fs_out : Fs_in = 1 : 2 */
            S->FIR_Fracs = 1;
            S->FIR_Order = RESAMPLER_DOWN_ORDER_FIR1;
            S->Coefs = silk_Resampler_1_2_COEFS;
        } else if( silk_MUL( Fs_Hz_out, 3 ) == Fs_Hz_in ) {                     /* Fs_out : Fs_in = 1 : 3 */
            S->FIR_Fracs = 1;
            S->FIR_Order = RESAMPLER_DOWN_ORDER_FIR2;
            S->Coefs = silk_Resampler_1_3_COEFS;
        } else if( silk_MUL( Fs_Hz_out, 4 ) == Fs_Hz_in ) {                     /* Fs_out : Fs_in = 1 : 4 */
            S->FIR_Fracs = 1;
            S->FIR_Order = RESAMPLER_DOWN_ORDER_FIR2;
            S->Coefs = silk_Resampler_1_4_COEFS;
        } else if( silk_MUL( Fs_Hz_out, 6 ) == Fs_Hz_in ) {                     /* Fs_out : Fs_in = 1 : 6 */
            S->FIR_Fracs = 1;
            S->FIR_Order = RESAMPLER_DOWN_ORDER_FIR2;
            S->Coefs = silk_Resampler_1_6_COEFS;
        } else {
            /* None available */
            silk_assert( 0 );
            return -1;
        }
    } else {
        /* Input and output sampling rates are equal: copy */
        S->resampler_function = USE_silk_resampler_copy;
    }

    /* Ratio of input/output samples */
    S->invRatio_Q16 = silk_LSHIFT32( silk_DIV32( silk_LSHIFT32( Fs_Hz_in, 14 + up2x ), Fs_Hz_out ), 2 );
    /* Make sure the ratio is rounded up */
    while( silk_SMULWW( S->invRatio_Q16, Fs_Hz_out ) < silk_LSHIFT32( Fs_Hz_in, up2x ) ) {
        S->invRatio_Q16++;
    }

    return 0;
}

/* Resampler: convert from one sampling rate to another */
/* Input and output sampling rate are at most 48000 Hz  */
opus_int silk_resampler(
    silk_resampler_state_struct *S,                 /* I/O  Resampler state                                             */
    opus_int16                  out[],              /* O    Output signal                                               */
    const opus_int16            in[],               /* I    Input signal                                                */
    opus_int32                  inLen               /* I    Number of input samples                                     */
)
{
    opus_int nSamples;

    /* Need at least 1 ms of input data */
    silk_assert( inLen >= S->Fs_in_kHz );
    /* Delay can't exceed the 1 ms of buffering */
    silk_assert( S->inputDelay <= S->Fs_in_kHz );

    nSamples = S->Fs_in_kHz - S->inputDelay;

    /* Copy to delay buffer */
    silk_memcpy( &S->delayBuf[ S->inputDelay ], in, nSamples * sizeof( opus_int16 ) );

    switch( S->resampler_function ) {
        case USE_silk_resampler_private_up2_HQ_wrapper:
            silk_resampler_private_up2_HQ_wrapper( S, out, S->delayBuf, S->Fs_in_kHz );
            silk_resampler_private_up2_HQ_wrapper( S, &out[ S->Fs_out_kHz ], &in[ nSamples ], inLen - S->Fs_in_kHz );
            break;
        case USE_silk_resampler_private_IIR_FIR:
            silk_resampler_private_IIR_FIR( S, out, S->delayBuf, S->Fs_in_kHz );
            silk_resampler_private_IIR_FIR( S, &out[ S->Fs_out_kHz ], &in[ nSamples ], inLen - S->Fs_in_kHz );
            break;
        case USE_silk_resampler_private_down_FIR:
            silk_resampler_private_down_FIR( S, out, S->delayBuf, S->Fs_in_kHz );
            silk_resampler_private_down_FIR( S, &out[ S->Fs_out_kHz ], &in[ nSamples ], inLen - S->Fs_in_kHz );
            break;
        default:
            silk_memcpy( out, S->delayBuf, S->Fs_in_kHz * sizeof( opus_int16 ) );
            silk_memcpy( &out[ S->Fs_out_kHz ], &in[ nSamples ], ( inLen - S->Fs_in_kHz ) * sizeof( opus_int16 ) );
    }

    /* Copy to delay buffer */
    silk_memcpy( S->delayBuf, &in[ inLen - S->inputDelay ], S->inputDelay * sizeof( opus_int16 ) );

    return 0;
}