Laxmi Kant Tiwari
CMSIS DSP Lib
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Diff: cmsis_dsp/TransformFunctions/arm_dct4_q15.c
- Revision:
- 1:fdd22bb7aa52
- Child:
- 2:da51fb522205
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/cmsis_dsp/TransformFunctions/arm_dct4_q15.c Wed Nov 28 12:30:09 2012 +0000
@@ -0,0 +1,386 @@
+/* ----------------------------------------------------------------------
+* Copyright (C) 2010 ARM Limited. All rights reserved.
+*
+* $Date: 15. February 2012
+* $Revision: V1.1.0
+*
+* Project: CMSIS DSP Library
+* Title: arm_dct4_q15.c
+*
+* Description: Processing function of DCT4 & IDCT4 Q15.
+*
+* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
+*
+* Version 1.1.0 2012/02/15
+* Updated with more optimizations, bug fixes and minor API changes.
+*
+* Version 1.0.10 2011/7/15
+* Big Endian support added and Merged M0 and M3/M4 Source code.
+*
+* Version 1.0.3 2010/11/29
+* Re-organized the CMSIS folders and updated documentation.
+*
+* Version 1.0.2 2010/11/11
+* Documentation updated.
+*
+* Version 1.0.1 2010/10/05
+* Production release and review comments incorporated.
+*
+* Version 1.0.0 2010/09/20
+* Production release and review comments incorporated.
+* -------------------------------------------------------------------- */
+
+#include "arm_math.h"
+
+/**
+ * @addtogroup DCT4_IDCT4
+ * @{
+ */
+
+/**
+ * @brief Processing function for the Q15 DCT4/IDCT4.
+ * @param[in] *S points to an instance of the Q15 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:
+ * 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 dct4FormatsQ15Table.gif
+ */
+
+void arm_dct4_q15(
+ const arm_dct4_instance_q15 * S,
+ q15_t * pState,
+ q15_t * pInlineBuffer)
+{
+ uint32_t i; /* Loop counter */
+ q15_t *weights = S->pTwiddle; /* Pointer to the Weights table */
+ q15_t *cosFact = S->pCosFactor; /* Pointer to the cos factors table */
+ q15_t *pS1, *pS2, *pbuff; /* Temporary pointers for input buffer and pState buffer */
+ q15_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_q15(pInlineBuffer, cosFact, pInlineBuffer, S->N);
+ arm_shift_q15(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
+
+ /* Run the below code for Cortex-M4 and Cortex-M3 */
+
+ /* Initializing the loop counter to N/2 >> 2 for loop unrolling by 4 */
+ i = (uint32_t) 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 = (uint32_t) 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_q15(S->pRfft, pInlineBuffer, pState);
+
+ /*----------------------------------------------------------------------
+ * Step3: Multiply the FFT output with the weights.
+ *----------------------------------------------------------------------*/
+ arm_cmplx_mult_cmplx_q15(pState, weights, pState, S->N);
+
+ /* The output of complex multiplication is in 3.13 format.
+ * Hence changing the format of N (i.e. 2*N elements) complex numbers to 1.15 format by shifting left by 2 bits. */
+ arm_shift_q15(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 = ((uint32_t) 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 = ((uint32_t) 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 = (uint32_t) 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++ = ((q15_t) (((q31_t) in * S->normalize) >> 15));
+
+ in = *pbuff;
+ *pbuff++ = ((q15_t) (((q31_t) in * S->normalize) >> 15));
+
+ in = *pbuff;
+ *pbuff++ = ((q15_t) (((q31_t) in * S->normalize) >> 15));
+
+ in = *pbuff;
+ *pbuff++ = ((q15_t) (((q31_t) in * S->normalize) >> 15));
+
+ /* Decrement the loop counter */
+ i--;
+ } while(i > 0u);
+
+
+#else
+
+ /* Run the below code for Cortex-M0 */
+
+ /* Initializing the loop counter to N/2 */
+ i = (uint32_t) 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 = (uint32_t) 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_q15(S->pRfft, pInlineBuffer, pState);
+
+ /*----------------------------------------------------------------------
+ * Step3: Multiply the FFT output with the weights.
+ *----------------------------------------------------------------------*/
+ arm_cmplx_mult_cmplx_q15(pState, weights, pState, S->N);
+
+ /* The output of complex multiplication is in 3.13 format.
+ * Hence changing the format of N (i.e. 2*N elements) complex numbers to 1.15 format by shifting left by 2 bits. */
+ arm_shift_q15(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 */
+ i = ((uint32_t) S->N - 1u);
+
+ /* 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++;
+
+ 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++;
+
+ /* Decrement the loop counter */
+ i--;
+ } while(i > 0u);
+
+ /*------------ Normalizing the output by multiplying with the normalizing factor ----------*/
+
+ /* Initializing the loop counter */
+ i = (uint32_t) 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++ = ((q15_t) (((q31_t) in * S->normalize) >> 15));
+
+ /* Decrement the loop counter */
+ i--;
+ } while(i > 0u);
+
+#endif /* #ifndef ARM_MATH_CM0 */
+
+}
+
+/**
+ * @} end of DCT4_IDCT4 group
+ */