+++ /dev/null
-/* ----------------------------------------------------------------------
-* Copyright (C) 2010-2013 ARM Limited. All rights reserved.
-*
-* $Date: 17. January 2013
-* $Revision: V1.4.1
-*
-* Project: CMSIS DSP Library
-* Title: arm_dct4_q31.c
-*
-* Description: Processing function of DCT4 & IDCT4 Q31.
-*
-* 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"
-
-/**
- * @addtogroup DCT4_IDCT4
- * @{
- */
-
-/**
- * @brief Processing function for the Q31 DCT4/IDCT4.
- * @param[in] *S points to an instance of the Q31 DCT4 structure.
- * @param[in] *pState points to state buffer.
- * @param[in,out] *pInlineBuffer points to the in-place input and output buffer.
- * @return none.
- * \par Input an output formats:
- * Input samples need to be downscaled by 1 bit to avoid saturations in the Q31 DCT process,
- * as the conversion from DCT2 to DCT4 involves one subtraction.
- * Internally inputs are downscaled in the RFFT process function to avoid overflows.
- * Number of bits downscaled, depends on the size of the transform.
- * The input and output formats for different DCT sizes and number of bits to upscale are mentioned in the table below:
- *
- * \image html dct4FormatsQ31Table.gif
- */
-
-void arm_dct4_q31(
- const arm_dct4_instance_q31 * S,
- q31_t * pState,
- q31_t * pInlineBuffer)
-{
- uint16_t i; /* Loop counter */
- q31_t *weights = S->pTwiddle; /* Pointer to the Weights table */
- q31_t *cosFact = S->pCosFactor; /* Pointer to the cos factors table */
- q31_t *pS1, *pS2, *pbuff; /* Temporary pointers for input buffer and pState buffer */
- q31_t in; /* Temporary variable */
-
-
- /* DCT4 computation involves DCT2 (which is calculated using RFFT)
- * along with some pre-processing and post-processing.
- * Computational procedure is explained as follows:
- * (a) Pre-processing involves multiplying input with cos factor,
- * r(n) = 2 * u(n) * cos(pi*(2*n+1)/(4*n))
- * where,
- * r(n) -- output of preprocessing
- * u(n) -- input to preprocessing(actual Source buffer)
- * (b) Calculation of DCT2 using FFT is divided into three steps:
- * Step1: Re-ordering of even and odd elements of input.
- * Step2: Calculating FFT of the re-ordered input.
- * Step3: Taking the real part of the product of FFT output and weights.
- * (c) Post-processing - DCT4 can be obtained from DCT2 output using the following equation:
- * Y4(k) = Y2(k) - Y4(k-1) and Y4(-1) = Y4(0)
- * where,
- * Y4 -- DCT4 output, Y2 -- DCT2 output
- * (d) Multiplying the output with the normalizing factor sqrt(2/N).
- */
-
- /*-------- Pre-processing ------------*/
- /* Multiplying input with cos factor i.e. r(n) = 2 * x(n) * cos(pi*(2*n+1)/(4*n)) */
- arm_mult_q31(pInlineBuffer, cosFact, pInlineBuffer, S->N);
- arm_shift_q31(pInlineBuffer, 1, pInlineBuffer, S->N);
-
- /* ----------------------------------------------------------------
- * Step1: Re-ordering of even and odd elements as
- * pState[i] = pInlineBuffer[2*i] and
- * pState[N-i-1] = pInlineBuffer[2*i+1] where i = 0 to N/2
- ---------------------------------------------------------------------*/
-
- /* pS1 initialized to pState */
- pS1 = pState;
-
- /* pS2 initialized to pState+N-1, so that it points to the end of the state buffer */
- pS2 = pState + (S->N - 1u);
-
- /* pbuff initialized to input buffer */
- pbuff = pInlineBuffer;
-
-#ifndef ARM_MATH_CM0_FAMILY
-
- /* Run the below code for Cortex-M4 and Cortex-M3 */
-
- /* Initializing the loop counter to N/2 >> 2 for loop unrolling by 4 */
- i = S->Nby2 >> 2u;
-
- /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
- ** a second loop below computes the remaining 1 to 3 samples. */
- do
- {
- /* Re-ordering of even and odd elements */
- /* pState[i] = pInlineBuffer[2*i] */
- *pS1++ = *pbuff++;
- /* pState[N-i-1] = pInlineBuffer[2*i+1] */
- *pS2-- = *pbuff++;
-
- *pS1++ = *pbuff++;
- *pS2-- = *pbuff++;
-
- *pS1++ = *pbuff++;
- *pS2-- = *pbuff++;
-
- *pS1++ = *pbuff++;
- *pS2-- = *pbuff++;
-
- /* Decrement the loop counter */
- i--;
- } while(i > 0u);
-
- /* pbuff initialized to input buffer */
- pbuff = pInlineBuffer;
-
- /* pS1 initialized to pState */
- pS1 = pState;
-
- /* Initializing the loop counter to N/4 instead of N for loop unrolling */
- i = S->N >> 2u;
-
- /* Processing with loop unrolling 4 times as N is always multiple of 4.
- * Compute 4 outputs at a time */
- do
- {
- /* Writing the re-ordered output back to inplace input buffer */
- *pbuff++ = *pS1++;
- *pbuff++ = *pS1++;
- *pbuff++ = *pS1++;
- *pbuff++ = *pS1++;
-
- /* Decrement the loop counter */
- i--;
- } while(i > 0u);
-
-
- /* ---------------------------------------------------------
- * Step2: Calculate RFFT for N-point input
- * ---------------------------------------------------------- */
- /* pInlineBuffer is real input of length N , pState is the complex output of length 2N */
- arm_rfft_q31(S->pRfft, pInlineBuffer, pState);
-
- /*----------------------------------------------------------------------
- * Step3: Multiply the FFT output with the weights.
- *----------------------------------------------------------------------*/
- arm_cmplx_mult_cmplx_q31(pState, weights, pState, S->N);
-
- /* The output of complex multiplication is in 3.29 format.
- * Hence changing the format of N (i.e. 2*N elements) complex numbers to 1.31 format by shifting left by 2 bits. */
- arm_shift_q31(pState, 2, pState, S->N * 2);
-
- /* ----------- Post-processing ---------- */
- /* DCT-IV can be obtained from DCT-II by the equation,
- * Y4(k) = Y2(k) - Y4(k-1) and Y4(-1) = Y4(0)
- * Hence, Y4(0) = Y2(0)/2 */
- /* Getting only real part from the output and Converting to DCT-IV */
-
- /* Initializing the loop counter to N >> 2 for loop unrolling by 4 */
- i = (S->N - 1u) >> 2u;
-
- /* pbuff initialized to input buffer. */
- pbuff = pInlineBuffer;
-
- /* pS1 initialized to pState */
- pS1 = pState;
-
- /* Calculating Y4(0) from Y2(0) using Y4(0) = Y2(0)/2 */
- in = *pS1++ >> 1u;
- /* input buffer acts as inplace, so output values are stored in the input itself. */
- *pbuff++ = in;
-
- /* pState pointer is incremented twice as the real values are located alternatively in the array */
- pS1++;
-
- /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
- ** a second loop below computes the remaining 1 to 3 samples. */
- do
- {
- /* Calculating Y4(1) to Y4(N-1) from Y2 using equation Y4(k) = Y2(k) - Y4(k-1) */
- /* pState pointer (pS1) is incremented twice as the real values are located alternatively in the array */
- in = *pS1++ - in;
- *pbuff++ = in;
- /* points to the next real value */
- pS1++;
-
- in = *pS1++ - in;
- *pbuff++ = in;
- pS1++;
-
- in = *pS1++ - in;
- *pbuff++ = in;
- pS1++;
-
- in = *pS1++ - in;
- *pbuff++ = in;
- pS1++;
-
- /* Decrement the loop counter */
- i--;
- } while(i > 0u);
-
- /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
- ** No loop unrolling is used. */
- i = (S->N - 1u) % 0x4u;
-
- while(i > 0u)
- {
- /* Calculating Y4(1) to Y4(N-1) from Y2 using equation Y4(k) = Y2(k) - Y4(k-1) */
- /* pState pointer (pS1) is incremented twice as the real values are located alternatively in the array */
- in = *pS1++ - in;
- *pbuff++ = in;
- /* points to the next real value */
- pS1++;
-
- /* Decrement the loop counter */
- i--;
- }
-
-
- /*------------ Normalizing the output by multiplying with the normalizing factor ----------*/
-
- /* Initializing the loop counter to N/4 instead of N for loop unrolling */
- i = S->N >> 2u;
-
- /* pbuff initialized to the pInlineBuffer(now contains the output values) */
- pbuff = pInlineBuffer;
-
- /* Processing with loop unrolling 4 times as N is always multiple of 4. Compute 4 outputs at a time */
- do
- {
- /* Multiplying pInlineBuffer with the normalizing factor sqrt(2/N) */
- in = *pbuff;
- *pbuff++ = ((q31_t) (((q63_t) in * S->normalize) >> 31));
-
- in = *pbuff;
- *pbuff++ = ((q31_t) (((q63_t) in * S->normalize) >> 31));
-
- in = *pbuff;
- *pbuff++ = ((q31_t) (((q63_t) in * S->normalize) >> 31));
-
- in = *pbuff;
- *pbuff++ = ((q31_t) (((q63_t) in * S->normalize) >> 31));
-
- /* Decrement the loop counter */
- i--;
- } while(i > 0u);
-
-
-#else
-
- /* Run the below code for Cortex-M0 */
-
- /* Initializing the loop counter to N/2 */
- i = S->Nby2;
-
- do
- {
- /* Re-ordering of even and odd elements */
- /* pState[i] = pInlineBuffer[2*i] */
- *pS1++ = *pbuff++;
- /* pState[N-i-1] = pInlineBuffer[2*i+1] */
- *pS2-- = *pbuff++;
-
- /* Decrement the loop counter */
- i--;
- } while(i > 0u);
-
- /* pbuff initialized to input buffer */
- pbuff = pInlineBuffer;
-
- /* pS1 initialized to pState */
- pS1 = pState;
-
- /* Initializing the loop counter */
- i = S->N;
-
- do
- {
- /* Writing the re-ordered output back to inplace input buffer */
- *pbuff++ = *pS1++;
-
- /* Decrement the loop counter */
- i--;
- } while(i > 0u);
-
-
- /* ---------------------------------------------------------
- * Step2: Calculate RFFT for N-point input
- * ---------------------------------------------------------- */
- /* pInlineBuffer is real input of length N , pState is the complex output of length 2N */
- arm_rfft_q31(S->pRfft, pInlineBuffer, pState);
-
- /*----------------------------------------------------------------------
- * Step3: Multiply the FFT output with the weights.
- *----------------------------------------------------------------------*/
- arm_cmplx_mult_cmplx_q31(pState, weights, pState, S->N);
-
- /* The output of complex multiplication is in 3.29 format.
- * Hence changing the format of N (i.e. 2*N elements) complex numbers to 1.31 format by shifting left by 2 bits. */
- arm_shift_q31(pState, 2, pState, S->N * 2);
-
- /* ----------- Post-processing ---------- */
- /* DCT-IV can be obtained from DCT-II by the equation,
- * Y4(k) = Y2(k) - Y4(k-1) and Y4(-1) = Y4(0)
- * Hence, Y4(0) = Y2(0)/2 */
- /* Getting only real part from the output and Converting to DCT-IV */
-
- /* pbuff initialized to input buffer. */
- pbuff = pInlineBuffer;
-
- /* pS1 initialized to pState */
- pS1 = pState;
-
- /* Calculating Y4(0) from Y2(0) using Y4(0) = Y2(0)/2 */
- in = *pS1++ >> 1u;
- /* input buffer acts as inplace, so output values are stored in the input itself. */
- *pbuff++ = in;
-
- /* pState pointer is incremented twice as the real values are located alternatively in the array */
- pS1++;
-
- /* Initializing the loop counter */
- i = (S->N - 1u);
-
- while(i > 0u)
- {
- /* Calculating Y4(1) to Y4(N-1) from Y2 using equation Y4(k) = Y2(k) - Y4(k-1) */
- /* pState pointer (pS1) is incremented twice as the real values are located alternatively in the array */
- in = *pS1++ - in;
- *pbuff++ = in;
- /* points to the next real value */
- pS1++;
-
- /* Decrement the loop counter */
- i--;
- }
-
-
- /*------------ Normalizing the output by multiplying with the normalizing factor ----------*/
-
- /* Initializing the loop counter */
- i = S->N;
-
- /* pbuff initialized to the pInlineBuffer(now contains the output values) */
- pbuff = pInlineBuffer;
-
- do
- {
- /* Multiplying pInlineBuffer with the normalizing factor sqrt(2/N) */
- in = *pbuff;
- *pbuff++ = ((q31_t) (((q63_t) in * S->normalize) >> 31));
-
- /* Decrement the loop counter */
- i--;
- } while(i > 0u);
-
-#endif /* #ifndef ARM_MATH_CM0_FAMILY */
-
-}
-
-/**
- * @} end of DCT4_IDCT4 group
- */
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