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Diffstat (limited to 'Drivers/CMSIS/DSP/Source/TransformFunctions/arm_dct4_q31.c')
| -rw-r--r-- | Drivers/CMSIS/DSP/Source/TransformFunctions/arm_dct4_q31.c | 383 |
1 files changed, 383 insertions, 0 deletions
diff --git a/Drivers/CMSIS/DSP/Source/TransformFunctions/arm_dct4_q31.c b/Drivers/CMSIS/DSP/Source/TransformFunctions/arm_dct4_q31.c new file mode 100644 index 0000000..5757083 --- /dev/null +++ b/Drivers/CMSIS/DSP/Source/TransformFunctions/arm_dct4_q31.c @@ -0,0 +1,383 @@ +/* ----------------------------------------------------------------------
+ * Project: CMSIS DSP Library
+ * Title: arm_dct4_q31.c
+ * Description: Processing function of DCT4 & IDCT4 Q31
+ *
+ * $Date: 18. March 2019
+ * $Revision: V1.6.0
+ *
+ * Target Processor: Cortex-M cores
+ * -------------------------------------------------------------------- */
+/*
+ * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the License); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an AS IS BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#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)
+{
+ const q31_t *weights = S->pTwiddle; /* Pointer to the Weights table */
+ const 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 */
+ uint32_t i; /* Loop counter */
+
+
+ /* 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;
+
+
+#if defined (ARM_MATH_LOOPUNROLL)
+
+ /* 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 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 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 loop counter */
+ i--;
+ } while (i > 0U);
+
+
+#else
+
+ /* 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 loop counter */
+ i--;
+ }
+
+ /*------------ Normalizing the output by multiplying with the normalizing factor ----------*/
+
+ /* Initializing 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 loop counter */
+ i--;
+ } while (i > 0U);
+
+#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
+
+}
+
+/**
+ @} end of DCT4_IDCT4 group
+ */
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