freeswitch/libs/silk/src/SKP_Silk_resampler.c

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/*																		*
 * File Name:	SKP_Silk_resampler.c									*
 *																		*
 * Description: Interface to collection of resamplers					*
 *                                                                      *
 * Copyright 2010 (c), Skype Limited                                    *
 * All rights reserved.													*
 *                                                                      */

/* 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 "SKP_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 SKP_Silk_resampler_init(
	SKP_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( SKP_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 = SKP_Silk_resampler_private_down4;
    } else if( Fs_Hz_in > 48000 ) {
		S->nPreDownsamplers = 1;
        S->down_pre_function = SKP_Silk_resampler_down2;
    } else {
		S->nPreDownsamplers = 0;
        S->down_pre_function = NULL;
    }

	if( Fs_Hz_out > 96000 ) {
		S->nPostUpsamplers = 2;
        S->up_post_function = SKP_Silk_resampler_private_up4;
    } else if( Fs_Hz_out > 48000 ) {
		S->nPostUpsamplers = 1;
        S->up_post_function = SKP_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 = SKP_Silk_resampler_private_up2_HQ_wrapper;
        } else {
	        /* Default resampler */
	        S->resampler_function = SKP_Silk_resampler_private_IIR_FIR;
            up2 = 1;
            if( Fs_Hz_in > 24000 ) {
                /* Low-quality all-pass upsampler */
                S->up2_function = SKP_Silk_resampler_up2;
            } else {
                /* High-quality all-pass upsampler */
                S->up2_function = SKP_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 = SKP_Silk_Resampler_3_4_COEFS;
	    S->resampler_function = SKP_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 = SKP_Silk_Resampler_2_3_COEFS;
	    S->resampler_function = SKP_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 = SKP_Silk_Resampler_1_2_COEFS;
	    S->resampler_function = SKP_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 = SKP_Silk_Resampler_3_8_COEFS;
	    S->resampler_function = SKP_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 = SKP_Silk_Resampler_1_3_COEFS;
	    S->resampler_function = SKP_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 = SKP_Silk_Resampler_1_2_COEFS;
            S->resampler_function = SKP_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 = SKP_Silk_Resampler_1_3_COEFS;
            S->resampler_function = SKP_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 = SKP_Silk_Resampler_80_441_ARMA4_COEFS;
	    S->resampler_function = SKP_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 = SKP_Silk_Resampler_120_441_ARMA4_COEFS;
	    S->resampler_function = SKP_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 = SKP_Silk_Resampler_160_441_ARMA4_COEFS;
	    S->resampler_function = SKP_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 = SKP_Silk_Resampler_240_441_ARMA4_COEFS;
	    S->resampler_function = SKP_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 = SKP_Silk_Resampler_320_441_ARMA4_COEFS;
	    S->resampler_function = SKP_Silk_resampler_private_IIR_FIR;
        } else {
	        /* Default resampler */
	        S->resampler_function = SKP_Silk_resampler_private_IIR_FIR;
            up2 = 1;
            if( Fs_Hz_in > 24000 ) {
                /* Low-quality all-pass upsampler */
                S->up2_function = SKP_Silk_resampler_up2;
            } else {
                /* High-quality all-pass upsampler */
                S->up2_function = SKP_Silk_resampler_private_up2_HQ;
            }
        }
    } else {
        /* Input and output sampling rates are equal: copy */
        S->resampler_function = SKP_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 SKP_Silk_resampler_clear(
	SKP_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 SKP_Silk_resampler(
	SKP_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;
}