arm_rfft_q15.c

/* ----------------------------------------------------------------------    
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
*    
* $Date:        19. March 2015 
* $Revision: 	V.1.4.5  
*    
* Project: 	    CMSIS DSP Library    
* Title:	    arm_rfft_q15.c    
*    
* Description:	RFFT & RIFFT Q15 process function    
*    
*    
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*  
* Redistribution and use in source and binary forms, with or without 
* modification, are permitted provided that the following conditions
* are met:
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the 
*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.     
* -------------------------------------------------------------------- */

#include "arm_math.h"

/*--------------------------------------------------------------------    
*		Internal functions prototypes    
--------------------------------------------------------------------*/

void arm_split_rfft_q15(
    q15_t * pSrc,
    uint32_t fftLen,
    q15_t * pATable,
    q15_t * pBTable,
    q15_t * pDst,
    uint32_t modifier);

void arm_split_rifft_q15(
    q15_t * pSrc,
    uint32_t fftLen,
    q15_t * pATable,
    q15_t * pBTable,
    q15_t * pDst,
    uint32_t modifier);

/**    
* @addtogroup RealFFT    
* @{    
*/

/**    
* @brief Processing function for the Q15 RFFT/RIFFT.   
* @param[in]  *S    points to an instance of the Q15 RFFT/RIFFT structure.   
* @param[in]  *pSrc points to the input buffer.   
* @param[out] *pDst points to the output buffer.   
* @return none.   
*    
* \par Input an output formats:   
* \par    
* Internally input is downscaled by 2 for every stage to avoid saturations inside CFFT/CIFFT process.    
* Hence the output format is different for different RFFT sizes.    
* The input and output formats for different RFFT sizes and number of bits to upscale are mentioned in the tables below for RFFT and RIFFT:   
* \par    
* \image html RFFTQ15.gif "Input and Output Formats for Q15 RFFT"    
* \par    
* \image html RIFFTQ15.gif "Input and Output Formats for Q15 RIFFT"    
*/

void arm_rfft_q15(
    const arm_rfft_instance_q15 * S,
    q15_t * pSrc,
    q15_t * pDst)
{
    const arm_cfft_instance_q15 *S_CFFT = S->pCfft;
    uint32_t i;
    uint32_t L2 = S->fftLenReal >> 1;

    /* Calculation of RIFFT of input */
    if(S->ifftFlagR == 1u)
    {
        /*  Real IFFT core process */
        arm_split_rifft_q15(pSrc, L2, S->pTwiddleAReal,
                            S->pTwiddleBReal, pDst, S->twidCoefRModifier);
        
        /* Complex IFFT process */
        arm_cfft_q15(S_CFFT, pDst, S->ifftFlagR, S->bitReverseFlagR);
        
        for(i=0;i<S->fftLenReal;i++)
        {
            pDst[i] = pDst[i] << 1;
        }
    }
    else
    {
        /* Calculation of RFFT of input */
        
        /* Complex FFT process */
        arm_cfft_q15(S_CFFT, pSrc, S->ifftFlagR, S->bitReverseFlagR);

        /*  Real FFT core process */
        arm_split_rfft_q15(pSrc, L2, S->pTwiddleAReal,
                            S->pTwiddleBReal, pDst, S->twidCoefRModifier);
    }
}

/**    
* @} end of RealFFT group    
*/

/**    
* @brief  Core Real FFT process    
* @param  *pSrc 				points to the input buffer.   
* @param  fftLen  				length of FFT.   
* @param  *pATable 			points to the A twiddle Coef buffer.    
* @param  *pBTable 			points to the B twiddle Coef buffer.   
* @param  *pDst 				points to the output buffer.   
* @param  modifier 	        twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.   
* @return none.    
* The function implements a Real FFT    
*/

void arm_split_rfft_q15(
    q15_t * pSrc,
    uint32_t fftLen,
    q15_t * pATable,
    q15_t * pBTable,
    q15_t * pDst,
    uint32_t modifier)
{
    uint32_t i;                                    /* Loop Counter */
    q31_t outR, outI;                              /* Temporary variables for output */
    q15_t *pCoefA, *pCoefB;                        /* Temporary pointers for twiddle factors */
    q15_t *pSrc1, *pSrc2;
#ifndef ARM_MATH_CM0_FAMILY
    q15_t *pD1, *pD2;
#endif

    //  pSrc[2u * fftLen] = pSrc[0]; 
    //  pSrc[(2u * fftLen) + 1u] = pSrc[1]; 

    pCoefA = &pATable[modifier * 2u];
    pCoefB = &pBTable[modifier * 2u];

    pSrc1 = &pSrc[2];
    pSrc2 = &pSrc[(2u * fftLen) - 2u];

#ifndef ARM_MATH_CM0_FAMILY

    /* Run the below code for Cortex-M4 and Cortex-M3 */
    i = 1u;
    pD1 = pDst + 2;
    pD2 = pDst + (4u * fftLen) - 2;

    for(i = fftLen - 1; i > 0; i--)
    {
        /*    
        outR = (pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1]    
        + pSrc[2 * n - 2 * i] * pBTable[2 * i] +    
        pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);    
        */

        /* outI = (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] +    
        pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -    
        pIn[2 * n - 2 * i + 1] * pBTable[2 * i]); */


#ifndef ARM_MATH_BIG_ENDIAN

        /* pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1] */
        outR = __SMUSD(*__SIMD32(pSrc1), *__SIMD32(pCoefA));

#else

        /* -(pSrc[2 * i + 1] * pATable[2 * i + 1] - pSrc[2 * i] * pATable[2 * i]) */
        outR = -(__SMUSD(*__SIMD32(pSrc1), *__SIMD32(pCoefA)));

#endif /*      #ifndef ARM_MATH_BIG_ENDIAN     */

        /* pSrc[2 * n - 2 * i] * pBTable[2 * i] +    
        pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]) */
        outR = __SMLAD(*__SIMD32(pSrc2), *__SIMD32(pCoefB), outR) >> 16u;

        /* pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -    
        pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */

#ifndef ARM_MATH_BIG_ENDIAN

        outI = __SMUSDX(*__SIMD32(pSrc2)--, *__SIMD32(pCoefB));

#else

        outI = __SMUSDX(*__SIMD32(pCoefB), *__SIMD32(pSrc2)--);

#endif /*      #ifndef ARM_MATH_BIG_ENDIAN     */

        /* (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] */
        outI = __SMLADX(*__SIMD32(pSrc1)++, *__SIMD32(pCoefA), outI);

        /* write output */
        *pD1++ = (q15_t) outR;
        *pD1++ = outI >> 16u;

        /* write complex conjugate output */
        pD2[0] = (q15_t) outR;
        pD2[1] = -(outI >> 16u);
        pD2 -= 2;

        /* update coefficient pointer */
        pCoefB = pCoefB + (2u * modifier);
        pCoefA = pCoefA + (2u * modifier);
    }

    pDst[2u * fftLen] = (pSrc[0] - pSrc[1]) >> 1;
    pDst[(2u * fftLen) + 1u] = 0;

    pDst[0] = (pSrc[0] + pSrc[1]) >> 1;
    pDst[1] = 0;

#else

    /* Run the below code for Cortex-M0 */
    i = 1u;

    while(i < fftLen)
    {
        /*    
        outR = (pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1]    
        + pSrc[2 * n - 2 * i] * pBTable[2 * i] +    
        pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);    
        */

        outR = *pSrc1 * *pCoefA;
        outR = outR - (*(pSrc1 + 1) * *(pCoefA + 1));
        outR = outR + (*pSrc2 * *pCoefB);
        outR = (outR + (*(pSrc2 + 1) * *(pCoefB + 1))) >> 16;


        /* outI = (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] +    
        pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -    
        pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);   
        */

        outI = *pSrc2 * *(pCoefB + 1);
        outI = outI - (*(pSrc2 + 1) * *pCoefB);
        outI = outI + (*(pSrc1 + 1) * *pCoefA);
        outI = outI + (*pSrc1 * *(pCoefA + 1));

        /* update input pointers */
        pSrc1 += 2u;
        pSrc2 -= 2u;

        /* write output */
        pDst[2u * i] = (q15_t) outR;
        pDst[(2u * i) + 1u] = outI >> 16u;

        /* write complex conjugate output */
        pDst[(4u * fftLen) - (2u * i)] = (q15_t) outR;
        pDst[((4u * fftLen) - (2u * i)) + 1u] = -(outI >> 16u);

        /* update coefficient pointer */
        pCoefB = pCoefB + (2u * modifier);
        pCoefA = pCoefA + (2u * modifier);

        i++;
    }

    pDst[2u * fftLen] = (pSrc[0] - pSrc[1]) >> 1;
    pDst[(2u * fftLen) + 1u] = 0;

    pDst[0] = (pSrc[0] + pSrc[1]) >> 1;
    pDst[1] = 0;

#endif /* #ifndef ARM_MATH_CM0_FAMILY */
}


/**    
* @brief  Core Real IFFT process    
* @param[in]   *pSrc 				points to the input buffer.    
* @param[in]   fftLen  		    length of FFT.   
* @param[in]   *pATable 			points to the twiddle Coef A buffer.   
* @param[in]   *pBTable 			points to the twiddle Coef B buffer.    
* @param[out]  *pDst 				points to the output buffer.   
* @param[in]   modifier 	        twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.   
* @return none.    
* The function implements a Real IFFT    
*/
void arm_split_rifft_q15(
    q15_t * pSrc,
    uint32_t fftLen,
    q15_t * pATable,
    q15_t * pBTable,
    q15_t * pDst,
    uint32_t modifier)
{
    uint32_t i;                                    /* Loop Counter */
    q31_t outR, outI;                              /* Temporary variables for output */
    q15_t *pCoefA, *pCoefB;                        /* Temporary pointers for twiddle factors */
    q15_t *pSrc1, *pSrc2;
    q15_t *pDst1 = &pDst[0];

    pCoefA = &pATable[0];
    pCoefB = &pBTable[0];

    pSrc1 = &pSrc[0];
    pSrc2 = &pSrc[2u * fftLen];

#ifndef ARM_MATH_CM0_FAMILY

    /* Run the below code for Cortex-M4 and Cortex-M3 */
    i = fftLen;

    while(i > 0u)
    {
        /*    
        outR = (pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +    
        pIn[2 * n - 2 * i] * pBTable[2 * i] -    
        pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);    

        outI = (pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] -    
        pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -    
        pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);    
        */


#ifndef ARM_MATH_BIG_ENDIAN

        /* pIn[2 * n - 2 * i] * pBTable[2 * i] -    
        pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]) */
        outR = __SMUSD(*__SIMD32(pSrc2), *__SIMD32(pCoefB));

#else

        /* -(-pIn[2 * n - 2 * i] * pBTable[2 * i] +  
        pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1])) */
        outR = -(__SMUSD(*__SIMD32(pSrc2), *__SIMD32(pCoefB)));

#endif /*      #ifndef ARM_MATH_BIG_ENDIAN     */

        /* pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +    
        pIn[2 * n - 2 * i] * pBTable[2 * i] */
        outR = __SMLAD(*__SIMD32(pSrc1), *__SIMD32(pCoefA), outR) >> 16u;

        /*    
        -pIn[2 * n - 2 * i] * pBTable[2 * i + 1] +    
        pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */
        outI = __SMUADX(*__SIMD32(pSrc2)--, *__SIMD32(pCoefB));

        /* pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] */

#ifndef ARM_MATH_BIG_ENDIAN

        outI = __SMLSDX(*__SIMD32(pCoefA), *__SIMD32(pSrc1)++, -outI);

#else

        outI = __SMLSDX(*__SIMD32(pSrc1)++, *__SIMD32(pCoefA), -outI);

#endif /*      #ifndef ARM_MATH_BIG_ENDIAN     */
        /* write output */

#ifndef ARM_MATH_BIG_ENDIAN

        *__SIMD32(pDst1)++ = __PKHBT(outR, (outI >> 16u), 16);

#else

        *__SIMD32(pDst1)++ = __PKHBT((outI >> 16u), outR, 16);

#endif /*      #ifndef ARM_MATH_BIG_ENDIAN     */

        /* update coefficient pointer */
        pCoefB = pCoefB + (2u * modifier);
        pCoefA = pCoefA + (2u * modifier);

        i--;
    }
#else
    /* Run the below code for Cortex-M0 */
    i = fftLen;

    while(i > 0u)
    {
        /*    
        outR = (pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +    
        pIn[2 * n - 2 * i] * pBTable[2 * i] -    
        pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);    
        */

        outR = *pSrc2 * *pCoefB;
        outR = outR - (*(pSrc2 + 1) * *(pCoefB + 1));
        outR = outR + (*pSrc1 * *pCoefA);
        outR = (outR + (*(pSrc1 + 1) * *(pCoefA + 1))) >> 16;

        /*   
        outI = (pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] -   
        pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -   
        pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);   
        */

        outI = *(pSrc1 + 1) * *pCoefA;
        outI = outI - (*pSrc1 * *(pCoefA + 1));
        outI = outI - (*pSrc2 * *(pCoefB + 1));
        outI = outI - (*(pSrc2 + 1) * *(pCoefB));

        /* update input pointers */
        pSrc1 += 2u;
        pSrc2 -= 2u;

        /* write output */
        *pDst1++ = (q15_t) outR;
        *pDst1++ = (q15_t) (outI >> 16);

        /* update coefficient pointer */
        pCoefB = pCoefB + (2u * modifier);
        pCoefA = pCoefA + (2u * modifier);

        i--;
    }
#endif /* #ifndef ARM_MATH_CM0_FAMILY */
}