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| <h1>arm_dct4_f32.c</h1> </div> |
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| <div class="contents"> |
| <a href="arm__dct4__f32_8c.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">/* ---------------------------------------------------------------------- </span> |
| <a name="l00002"></a>00002 <span class="comment">* Copyright (C) 2010 ARM Limited. All rights reserved. </span> |
| <a name="l00003"></a>00003 <span class="comment">* </span> |
| <a name="l00004"></a>00004 <span class="comment">* $Date: 15. July 2011 </span> |
| <a name="l00005"></a>00005 <span class="comment">* $Revision: V1.0.10 </span> |
| <a name="l00006"></a>00006 <span class="comment">* </span> |
| <a name="l00007"></a>00007 <span class="comment">* Project: CMSIS DSP Library </span> |
| <a name="l00008"></a>00008 <span class="comment">* Title: arm_dct4_f32.c </span> |
| <a name="l00009"></a>00009 <span class="comment">* </span> |
| <a name="l00010"></a>00010 <span class="comment">* Description: Processing function of DCT4 & IDCT4 F32. </span> |
| <a name="l00011"></a>00011 <span class="comment">* </span> |
| <a name="l00012"></a>00012 <span class="comment">* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0</span> |
| <a name="l00013"></a>00013 <span class="comment">* </span> |
| <a name="l00014"></a>00014 <span class="comment">* Version 1.0.10 2011/7/15 </span> |
| <a name="l00015"></a>00015 <span class="comment">* Big Endian support added and Merged M0 and M3/M4 Source code. </span> |
| <a name="l00016"></a>00016 <span class="comment">* </span> |
| <a name="l00017"></a>00017 <span class="comment">* Version 1.0.3 2010/11/29 </span> |
| <a name="l00018"></a>00018 <span class="comment">* Re-organized the CMSIS folders and updated documentation. </span> |
| <a name="l00019"></a>00019 <span class="comment">* </span> |
| <a name="l00020"></a>00020 <span class="comment">* Version 1.0.2 2010/11/11 </span> |
| <a name="l00021"></a>00021 <span class="comment">* Documentation updated. </span> |
| <a name="l00022"></a>00022 <span class="comment">* </span> |
| <a name="l00023"></a>00023 <span class="comment">* Version 1.0.1 2010/10/05 </span> |
| <a name="l00024"></a>00024 <span class="comment">* Production release and review comments incorporated. </span> |
| <a name="l00025"></a>00025 <span class="comment">* </span> |
| <a name="l00026"></a>00026 <span class="comment">* Version 1.0.0 2010/09/20 </span> |
| <a name="l00027"></a>00027 <span class="comment">* Production release and review comments incorporated. </span> |
| <a name="l00028"></a>00028 <span class="comment">* -------------------------------------------------------------------- */</span> |
| <a name="l00029"></a>00029 |
| <a name="l00030"></a>00030 <span class="preprocessor">#include "<a class="code" href="arm__math_8h.html">arm_math.h</a>"</span> |
| <a name="l00031"></a>00031 |
| <a name="l00126"></a><a class="code" href="group___d_c_t4___i_d_c_t4.html#gafd538d68886848bc090ec2b0d364cc81">00126</a> <span class="keywordtype">void</span> <a class="code" href="group___d_c_t4___i_d_c_t4.html#gafd538d68886848bc090ec2b0d364cc81" title="Processing function for the floating-point DCT4/IDCT4.">arm_dct4_f32</a>( |
| <a name="l00127"></a>00127 <span class="keyword">const</span> <a class="code" href="structarm__dct4__instance__f32.html" title="Instance structure for the floating-point DCT4/IDCT4 function.">arm_dct4_instance_f32</a> * S, |
| <a name="l00128"></a>00128 <a class="code" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715" title="32-bit floating-point type definition.">float32_t</a> * pState, |
| <a name="l00129"></a>00129 <a class="code" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715" title="32-bit floating-point type definition.">float32_t</a> * pInlineBuffer) |
| <a name="l00130"></a>00130 { |
| <a name="l00131"></a>00131 uint32_t i; <span class="comment">/* Loop counter */</span> |
| <a name="l00132"></a>00132 <a class="code" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715" title="32-bit floating-point type definition.">float32_t</a> *weights = S-><a class="code" href="structarm__dct4__instance__f32.html#ad13544aafad268588c62e3eb35ae662c">pTwiddle</a>; <span class="comment">/* Pointer to the Weights table */</span> |
| <a name="l00133"></a>00133 <a class="code" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715" title="32-bit floating-point type definition.">float32_t</a> *cosFact = S-><a class="code" href="structarm__dct4__instance__f32.html#a6da1187e070801e011ce5e0582efa861">pCosFactor</a>; <span class="comment">/* Pointer to the cos factors table */</span> |
| <a name="l00134"></a>00134 <a class="code" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715" title="32-bit floating-point type definition.">float32_t</a> *pS1, *pS2, *pbuff; <span class="comment">/* Temporary pointers for input buffer and pState buffer */</span> |
| <a name="l00135"></a>00135 <a class="code" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715" title="32-bit floating-point type definition.">float32_t</a> in; <span class="comment">/* Temporary variable */</span> |
| <a name="l00136"></a>00136 |
| <a name="l00137"></a>00137 |
| <a name="l00138"></a>00138 <span class="comment">/* DCT4 computation involves DCT2 (which is calculated using RFFT) </span> |
| <a name="l00139"></a>00139 <span class="comment"> * along with some pre-processing and post-processing. </span> |
| <a name="l00140"></a>00140 <span class="comment"> * Computational procedure is explained as follows: </span> |
| <a name="l00141"></a>00141 <span class="comment"> * (a) Pre-processing involves multiplying input with cos factor, </span> |
| <a name="l00142"></a>00142 <span class="comment"> * r(n) = 2 * u(n) * cos(pi*(2*n+1)/(4*n)) </span> |
| <a name="l00143"></a>00143 <span class="comment"> * where, </span> |
| <a name="l00144"></a>00144 <span class="comment"> * r(n) -- output of preprocessing </span> |
| <a name="l00145"></a>00145 <span class="comment"> * u(n) -- input to preprocessing(actual Source buffer) </span> |
| <a name="l00146"></a>00146 <span class="comment"> * (b) Calculation of DCT2 using FFT is divided into three steps: </span> |
| <a name="l00147"></a>00147 <span class="comment"> * Step1: Re-ordering of even and odd elements of input. </span> |
| <a name="l00148"></a>00148 <span class="comment"> * Step2: Calculating FFT of the re-ordered input. </span> |
| <a name="l00149"></a>00149 <span class="comment"> * Step3: Taking the real part of the product of FFT output and weights. </span> |
| <a name="l00150"></a>00150 <span class="comment"> * (c) Post-processing - DCT4 can be obtained from DCT2 output using the following equation: </span> |
| <a name="l00151"></a>00151 <span class="comment"> * Y4(k) = Y2(k) - Y4(k-1) and Y4(-1) = Y4(0) </span> |
| <a name="l00152"></a>00152 <span class="comment"> * where, </span> |
| <a name="l00153"></a>00153 <span class="comment"> * Y4 -- DCT4 output, Y2 -- DCT2 output </span> |
| <a name="l00154"></a>00154 <span class="comment"> * (d) Multiplying the output with the normalizing factor sqrt(2/N). </span> |
| <a name="l00155"></a>00155 <span class="comment"> */</span> |
| <a name="l00156"></a>00156 |
| <a name="l00157"></a>00157 <span class="comment">/*-------- Pre-processing ------------*/</span> |
| <a name="l00158"></a>00158 <span class="comment">/* Multiplying input with cos factor i.e. r(n) = 2 * x(n) * cos(pi*(2*n+1)/(4*n)) */</span> |
| <a name="l00159"></a>00159 <a class="code" href="group__scale.html#ga3487af88b112f682ee90589cd419e123" title="Multiplies a floating-point vector by a scalar.">arm_scale_f32</a>(pInlineBuffer, 2.0f, pInlineBuffer, S-><a class="code" href="structarm__dct4__instance__f32.html#a262b29a51c371b46efc89120e31ccf37">N</a>); |
| <a name="l00160"></a>00160 <a class="code" href="group___basic_mult.html#gaca3f0b8227da431ab29225b88888aa32" title="Floating-point vector multiplication.">arm_mult_f32</a>(pInlineBuffer, cosFact, pInlineBuffer, S-><a class="code" href="structarm__dct4__instance__f32.html#a262b29a51c371b46efc89120e31ccf37">N</a>); |
| <a name="l00161"></a>00161 |
| <a name="l00162"></a>00162 <span class="comment">/* ---------------------------------------------------------------- </span> |
| <a name="l00163"></a>00163 <span class="comment"> * Step1: Re-ordering of even and odd elements as, </span> |
| <a name="l00164"></a>00164 <span class="comment"> * pState[i] = pInlineBuffer[2*i] and </span> |
| <a name="l00165"></a>00165 <span class="comment"> * pState[N-i-1] = pInlineBuffer[2*i+1] where i = 0 to N/2 </span> |
| <a name="l00166"></a>00166 <span class="comment"> ---------------------------------------------------------------------*/</span> |
| <a name="l00167"></a>00167 |
| <a name="l00168"></a>00168 <span class="comment">/* pS1 initialized to pState */</span> |
| <a name="l00169"></a>00169 pS1 = pState; |
| <a name="l00170"></a>00170 |
| <a name="l00171"></a>00171 <span class="comment">/* pS2 initialized to pState+N-1, so that it points to the end of the state buffer */</span> |
| <a name="l00172"></a>00172 pS2 = pState + (S-><a class="code" href="structarm__dct4__instance__f32.html#a262b29a51c371b46efc89120e31ccf37">N</a> - 1u); |
| <a name="l00173"></a>00173 |
| <a name="l00174"></a>00174 <span class="comment">/* pbuff initialized to input buffer */</span> |
| <a name="l00175"></a>00175 pbuff = pInlineBuffer; |
| <a name="l00176"></a>00176 |
| <a name="l00177"></a>00177 <span class="preprocessor">#ifndef ARM_MATH_CM0</span> |
| <a name="l00178"></a>00178 <span class="preprocessor"></span> |
| <a name="l00179"></a>00179 <span class="comment">/* Run the below code for Cortex-M4 and Cortex-M3 */</span> |
| <a name="l00180"></a>00180 |
| <a name="l00181"></a>00181 <span class="comment">/* Initializing the loop counter to N/2 >> 2 for loop unrolling by 4 */</span> |
| <a name="l00182"></a>00182 i = (uint32_t) S-><a class="code" href="structarm__dct4__instance__f32.html#adb1ef2739ddbe62e5cdadc47455a4147">Nby2</a> >> 2u; |
| <a name="l00183"></a>00183 |
| <a name="l00184"></a>00184 <span class="comment">/* First part of the processing with loop unrolling. Compute 4 outputs at a time. </span> |
| <a name="l00185"></a>00185 <span class="comment"> ** a second loop below computes the remaining 1 to 3 samples. */</span> |
| <a name="l00186"></a>00186 <span class="keywordflow">do</span> |
| <a name="l00187"></a>00187 { |
| <a name="l00188"></a>00188 <span class="comment">/* Re-ordering of even and odd elements */</span> |
| <a name="l00189"></a>00189 <span class="comment">/* pState[i] = pInlineBuffer[2*i] */</span> |
| <a name="l00190"></a>00190 *pS1++ = *pbuff++; |
| <a name="l00191"></a>00191 <span class="comment">/* pState[N-i-1] = pInlineBuffer[2*i+1] */</span> |
| <a name="l00192"></a>00192 *pS2-- = *pbuff++; |
| <a name="l00193"></a>00193 |
| <a name="l00194"></a>00194 *pS1++ = *pbuff++; |
| <a name="l00195"></a>00195 *pS2-- = *pbuff++; |
| <a name="l00196"></a>00196 |
| <a name="l00197"></a>00197 *pS1++ = *pbuff++; |
| <a name="l00198"></a>00198 *pS2-- = *pbuff++; |
| <a name="l00199"></a>00199 |
| <a name="l00200"></a>00200 *pS1++ = *pbuff++; |
| <a name="l00201"></a>00201 *pS2-- = *pbuff++; |
| <a name="l00202"></a>00202 |
| <a name="l00203"></a>00203 <span class="comment">/* Decrement the loop counter */</span> |
| <a name="l00204"></a>00204 i--; |
| <a name="l00205"></a>00205 } <span class="keywordflow">while</span>(i > 0u); |
| <a name="l00206"></a>00206 |
| <a name="l00207"></a>00207 <span class="comment">/* pbuff initialized to input buffer */</span> |
| <a name="l00208"></a>00208 pbuff = pInlineBuffer; |
| <a name="l00209"></a>00209 |
| <a name="l00210"></a>00210 <span class="comment">/* pS1 initialized to pState */</span> |
| <a name="l00211"></a>00211 pS1 = pState; |
| <a name="l00212"></a>00212 |
| <a name="l00213"></a>00213 <span class="comment">/* Initializing the loop counter to N/4 instead of N for loop unrolling */</span> |
| <a name="l00214"></a>00214 i = (uint32_t) S->N >> 2u; |
| <a name="l00215"></a>00215 |
| <a name="l00216"></a>00216 <span class="comment">/* Processing with loop unrolling 4 times as N is always multiple of 4. </span> |
| <a name="l00217"></a>00217 <span class="comment"> * Compute 4 outputs at a time */</span> |
| <a name="l00218"></a>00218 <span class="keywordflow">do</span> |
| <a name="l00219"></a>00219 { |
| <a name="l00220"></a>00220 <span class="comment">/* Writing the re-ordered output back to inplace input buffer */</span> |
| <a name="l00221"></a>00221 *pbuff++ = *pS1++; |
| <a name="l00222"></a>00222 *pbuff++ = *pS1++; |
| <a name="l00223"></a>00223 *pbuff++ = *pS1++; |
| <a name="l00224"></a>00224 *pbuff++ = *pS1++; |
| <a name="l00225"></a>00225 |
| <a name="l00226"></a>00226 <span class="comment">/* Decrement the loop counter */</span> |
| <a name="l00227"></a>00227 i--; |
| <a name="l00228"></a>00228 } <span class="keywordflow">while</span>(i > 0u); |
| <a name="l00229"></a>00229 |
| <a name="l00230"></a>00230 |
| <a name="l00231"></a>00231 <span class="comment">/* --------------------------------------------------------- </span> |
| <a name="l00232"></a>00232 <span class="comment"> * Step2: Calculate RFFT for N-point input </span> |
| <a name="l00233"></a>00233 <span class="comment"> * ---------------------------------------------------------- */</span> |
| <a name="l00234"></a>00234 <span class="comment">/* pInlineBuffer is real input of length N , pState is the complex output of length 2N */</span> |
| <a name="l00235"></a>00235 <a class="code" href="group___r_f_f_t___r_i_f_f_t.html#ga3df1766d230532bc068fc4ed69d0fcdc" title="Processing function for the floating-point RFFT/RIFFT.">arm_rfft_f32</a>(S->pRfft, pInlineBuffer, pState); |
| <a name="l00236"></a>00236 |
| <a name="l00237"></a>00237 <span class="comment">/*---------------------------------------------------------------------- </span> |
| <a name="l00238"></a>00238 <span class="comment"> * Step3: Multiply the FFT output with the weights. </span> |
| <a name="l00239"></a>00239 <span class="comment"> *----------------------------------------------------------------------*/</span> |
| <a name="l00240"></a>00240 <a class="code" href="group___cmplx_by_cmplx_mult.html#ga14b47080054a1ba1250a86805be1ff6b" title="Floating-point complex-by-complex multiplication.">arm_cmplx_mult_cmplx_f32</a>(pState, weights, pState, S->N); |
| <a name="l00241"></a>00241 |
| <a name="l00242"></a>00242 <span class="comment">/* ----------- Post-processing ---------- */</span> |
| <a name="l00243"></a>00243 <span class="comment">/* DCT-IV can be obtained from DCT-II by the equation, </span> |
| <a name="l00244"></a>00244 <span class="comment"> * Y4(k) = Y2(k) - Y4(k-1) and Y4(-1) = Y4(0) </span> |
| <a name="l00245"></a>00245 <span class="comment"> * Hence, Y4(0) = Y2(0)/2 */</span> |
| <a name="l00246"></a>00246 <span class="comment">/* Getting only real part from the output and Converting to DCT-IV */</span> |
| <a name="l00247"></a>00247 |
| <a name="l00248"></a>00248 <span class="comment">/* Initializing the loop counter to N >> 2 for loop unrolling by 4 */</span> |
| <a name="l00249"></a>00249 i = ((uint32_t) S->N - 1u) >> 2u; |
| <a name="l00250"></a>00250 |
| <a name="l00251"></a>00251 <span class="comment">/* pbuff initialized to input buffer. */</span> |
| <a name="l00252"></a>00252 pbuff = pInlineBuffer; |
| <a name="l00253"></a>00253 |
| <a name="l00254"></a>00254 <span class="comment">/* pS1 initialized to pState */</span> |
| <a name="l00255"></a>00255 pS1 = pState; |
| <a name="l00256"></a>00256 |
| <a name="l00257"></a>00257 <span class="comment">/* Calculating Y4(0) from Y2(0) using Y4(0) = Y2(0)/2 */</span> |
| <a name="l00258"></a>00258 in = *pS1++ * (<a class="code" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715" title="32-bit floating-point type definition.">float32_t</a>) 0.5; |
| <a name="l00259"></a>00259 <span class="comment">/* input buffer acts as inplace, so output values are stored in the input itself. */</span> |
| <a name="l00260"></a>00260 *pbuff++ = in; |
| <a name="l00261"></a>00261 |
| <a name="l00262"></a>00262 <span class="comment">/* pState pointer is incremented twice as the real values are located alternatively in the array */</span> |
| <a name="l00263"></a>00263 pS1++; |
| <a name="l00264"></a>00264 |
| <a name="l00265"></a>00265 <span class="comment">/* First part of the processing with loop unrolling. Compute 4 outputs at a time. </span> |
| <a name="l00266"></a>00266 <span class="comment"> ** a second loop below computes the remaining 1 to 3 samples. */</span> |
| <a name="l00267"></a>00267 <span class="keywordflow">do</span> |
| <a name="l00268"></a>00268 { |
| <a name="l00269"></a>00269 <span class="comment">/* Calculating Y4(1) to Y4(N-1) from Y2 using equation Y4(k) = Y2(k) - Y4(k-1) */</span> |
| <a name="l00270"></a>00270 <span class="comment">/* pState pointer (pS1) is incremented twice as the real values are located alternatively in the array */</span> |
| <a name="l00271"></a>00271 in = *pS1++ - in; |
| <a name="l00272"></a>00272 *pbuff++ = in; |
| <a name="l00273"></a>00273 <span class="comment">/* points to the next real value */</span> |
| <a name="l00274"></a>00274 pS1++; |
| <a name="l00275"></a>00275 |
| <a name="l00276"></a>00276 in = *pS1++ - in; |
| <a name="l00277"></a>00277 *pbuff++ = in; |
| <a name="l00278"></a>00278 pS1++; |
| <a name="l00279"></a>00279 |
| <a name="l00280"></a>00280 in = *pS1++ - in; |
| <a name="l00281"></a>00281 *pbuff++ = in; |
| <a name="l00282"></a>00282 pS1++; |
| <a name="l00283"></a>00283 |
| <a name="l00284"></a>00284 in = *pS1++ - in; |
| <a name="l00285"></a>00285 *pbuff++ = in; |
| <a name="l00286"></a>00286 pS1++; |
| <a name="l00287"></a>00287 |
| <a name="l00288"></a>00288 <span class="comment">/* Decrement the loop counter */</span> |
| <a name="l00289"></a>00289 i--; |
| <a name="l00290"></a>00290 } <span class="keywordflow">while</span>(i > 0u); |
| <a name="l00291"></a>00291 |
| <a name="l00292"></a>00292 <span class="comment">/* If the blockSize is not a multiple of 4, compute any remaining output samples here. </span> |
| <a name="l00293"></a>00293 <span class="comment"> ** No loop unrolling is used. */</span> |
| <a name="l00294"></a>00294 i = ((uint32_t) S->N - 1u) % 0x4u; |
| <a name="l00295"></a>00295 |
| <a name="l00296"></a>00296 <span class="keywordflow">while</span>(i > 0u) |
| <a name="l00297"></a>00297 { |
| <a name="l00298"></a>00298 <span class="comment">/* Calculating Y4(1) to Y4(N-1) from Y2 using equation Y4(k) = Y2(k) - Y4(k-1) */</span> |
| <a name="l00299"></a>00299 <span class="comment">/* pState pointer (pS1) is incremented twice as the real values are located alternatively in the array */</span> |
| <a name="l00300"></a>00300 in = *pS1++ - in; |
| <a name="l00301"></a>00301 *pbuff++ = in; |
| <a name="l00302"></a>00302 <span class="comment">/* points to the next real value */</span> |
| <a name="l00303"></a>00303 pS1++; |
| <a name="l00304"></a>00304 |
| <a name="l00305"></a>00305 <span class="comment">/* Decrement the loop counter */</span> |
| <a name="l00306"></a>00306 i--; |
| <a name="l00307"></a>00307 } |
| <a name="l00308"></a>00308 |
| <a name="l00309"></a>00309 |
| <a name="l00310"></a>00310 <span class="comment">/*------------ Normalizing the output by multiplying with the normalizing factor ----------*/</span> |
| <a name="l00311"></a>00311 |
| <a name="l00312"></a>00312 <span class="comment">/* Initializing the loop counter to N/4 instead of N for loop unrolling */</span> |
| <a name="l00313"></a>00313 i = (uint32_t) S->N >> 2u; |
| <a name="l00314"></a>00314 |
| <a name="l00315"></a>00315 <span class="comment">/* pbuff initialized to the pInlineBuffer(now contains the output values) */</span> |
| <a name="l00316"></a>00316 pbuff = pInlineBuffer; |
| <a name="l00317"></a>00317 |
| <a name="l00318"></a>00318 <span class="comment">/* Processing with loop unrolling 4 times as N is always multiple of 4. Compute 4 outputs at a time */</span> |
| <a name="l00319"></a>00319 <span class="keywordflow">do</span> |
| <a name="l00320"></a>00320 { |
| <a name="l00321"></a>00321 <span class="comment">/* Multiplying pInlineBuffer with the normalizing factor sqrt(2/N) */</span> |
| <a name="l00322"></a>00322 in = *pbuff; |
| <a name="l00323"></a>00323 *pbuff++ = in * S->normalize; |
| <a name="l00324"></a>00324 |
| <a name="l00325"></a>00325 in = *pbuff; |
| <a name="l00326"></a>00326 *pbuff++ = in * S->normalize; |
| <a name="l00327"></a>00327 |
| <a name="l00328"></a>00328 in = *pbuff; |
| <a name="l00329"></a>00329 *pbuff++ = in * S->normalize; |
| <a name="l00330"></a>00330 |
| <a name="l00331"></a>00331 in = *pbuff; |
| <a name="l00332"></a>00332 *pbuff++ = in * S->normalize; |
| <a name="l00333"></a>00333 |
| <a name="l00334"></a>00334 <span class="comment">/* Decrement the loop counter */</span> |
| <a name="l00335"></a>00335 i--; |
| <a name="l00336"></a>00336 } <span class="keywordflow">while</span>(i > 0u); |
| <a name="l00337"></a>00337 |
| <a name="l00338"></a>00338 |
| <a name="l00339"></a>00339 <span class="preprocessor">#else</span> |
| <a name="l00340"></a>00340 <span class="preprocessor"></span> |
| <a name="l00341"></a>00341 <span class="comment">/* Run the below code for Cortex-M0 */</span> |
| <a name="l00342"></a>00342 |
| <a name="l00343"></a>00343 <span class="comment">/* Initializing the loop counter to N/2 */</span> |
| <a name="l00344"></a>00344 i = (uint32_t) S->Nby2; |
| <a name="l00345"></a>00345 |
| <a name="l00346"></a>00346 <span class="keywordflow">do</span> |
| <a name="l00347"></a>00347 { |
| <a name="l00348"></a>00348 <span class="comment">/* Re-ordering of even and odd elements */</span> |
| <a name="l00349"></a>00349 <span class="comment">/* pState[i] = pInlineBuffer[2*i] */</span> |
| <a name="l00350"></a>00350 *pS1++ = *pbuff++; |
| <a name="l00351"></a>00351 <span class="comment">/* pState[N-i-1] = pInlineBuffer[2*i+1] */</span> |
| <a name="l00352"></a>00352 *pS2-- = *pbuff++; |
| <a name="l00353"></a>00353 |
| <a name="l00354"></a>00354 <span class="comment">/* Decrement the loop counter */</span> |
| <a name="l00355"></a>00355 i--; |
| <a name="l00356"></a>00356 } <span class="keywordflow">while</span>(i > 0u); |
| <a name="l00357"></a>00357 |
| <a name="l00358"></a>00358 <span class="comment">/* pbuff initialized to input buffer */</span> |
| <a name="l00359"></a>00359 pbuff = pInlineBuffer; |
| <a name="l00360"></a>00360 |
| <a name="l00361"></a>00361 <span class="comment">/* pS1 initialized to pState */</span> |
| <a name="l00362"></a>00362 pS1 = pState; |
| <a name="l00363"></a>00363 |
| <a name="l00364"></a>00364 <span class="comment">/* Initializing the loop counter */</span> |
| <a name="l00365"></a>00365 i = (uint32_t) S->N; |
| <a name="l00366"></a>00366 |
| <a name="l00367"></a>00367 <span class="keywordflow">do</span> |
| <a name="l00368"></a>00368 { |
| <a name="l00369"></a>00369 <span class="comment">/* Writing the re-ordered output back to inplace input buffer */</span> |
| <a name="l00370"></a>00370 *pbuff++ = *pS1++; |
| <a name="l00371"></a>00371 |
| <a name="l00372"></a>00372 <span class="comment">/* Decrement the loop counter */</span> |
| <a name="l00373"></a>00373 i--; |
| <a name="l00374"></a>00374 } <span class="keywordflow">while</span>(i > 0u); |
| <a name="l00375"></a>00375 |
| <a name="l00376"></a>00376 |
| <a name="l00377"></a>00377 <span class="comment">/* --------------------------------------------------------- </span> |
| <a name="l00378"></a>00378 <span class="comment"> * Step2: Calculate RFFT for N-point input </span> |
| <a name="l00379"></a>00379 <span class="comment"> * ---------------------------------------------------------- */</span> |
| <a name="l00380"></a>00380 <span class="comment">/* pInlineBuffer is real input of length N , pState is the complex output of length 2N */</span> |
| <a name="l00381"></a>00381 <a class="code" href="group___r_f_f_t___r_i_f_f_t.html#ga3df1766d230532bc068fc4ed69d0fcdc" title="Processing function for the floating-point RFFT/RIFFT.">arm_rfft_f32</a>(S->pRfft, pInlineBuffer, pState); |
| <a name="l00382"></a>00382 |
| <a name="l00383"></a>00383 <span class="comment">/*---------------------------------------------------------------------- </span> |
| <a name="l00384"></a>00384 <span class="comment"> * Step3: Multiply the FFT output with the weights. </span> |
| <a name="l00385"></a>00385 <span class="comment"> *----------------------------------------------------------------------*/</span> |
| <a name="l00386"></a>00386 <a class="code" href="group___cmplx_by_cmplx_mult.html#ga14b47080054a1ba1250a86805be1ff6b" title="Floating-point complex-by-complex multiplication.">arm_cmplx_mult_cmplx_f32</a>(pState, weights, pState, S->N); |
| <a name="l00387"></a>00387 |
| <a name="l00388"></a>00388 <span class="comment">/* ----------- Post-processing ---------- */</span> |
| <a name="l00389"></a>00389 <span class="comment">/* DCT-IV can be obtained from DCT-II by the equation, </span> |
| <a name="l00390"></a>00390 <span class="comment"> * Y4(k) = Y2(k) - Y4(k-1) and Y4(-1) = Y4(0) </span> |
| <a name="l00391"></a>00391 <span class="comment"> * Hence, Y4(0) = Y2(0)/2 */</span> |
| <a name="l00392"></a>00392 <span class="comment">/* Getting only real part from the output and Converting to DCT-IV */</span> |
| <a name="l00393"></a>00393 |
| <a name="l00394"></a>00394 <span class="comment">/* pbuff initialized to input buffer. */</span> |
| <a name="l00395"></a>00395 pbuff = pInlineBuffer; |
| <a name="l00396"></a>00396 |
| <a name="l00397"></a>00397 <span class="comment">/* pS1 initialized to pState */</span> |
| <a name="l00398"></a>00398 pS1 = pState; |
| <a name="l00399"></a>00399 |
| <a name="l00400"></a>00400 <span class="comment">/* Calculating Y4(0) from Y2(0) using Y4(0) = Y2(0)/2 */</span> |
| <a name="l00401"></a>00401 in = *pS1++ * (<a class="code" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715" title="32-bit floating-point type definition.">float32_t</a>) 0.5; |
| <a name="l00402"></a>00402 <span class="comment">/* input buffer acts as inplace, so output values are stored in the input itself. */</span> |
| <a name="l00403"></a>00403 *pbuff++ = in; |
| <a name="l00404"></a>00404 |
| <a name="l00405"></a>00405 <span class="comment">/* pState pointer is incremented twice as the real values are located alternatively in the array */</span> |
| <a name="l00406"></a>00406 pS1++; |
| <a name="l00407"></a>00407 |
| <a name="l00408"></a>00408 <span class="comment">/* Initializing the loop counter */</span> |
| <a name="l00409"></a>00409 i = ((uint32_t) S->N - 1u); |
| <a name="l00410"></a>00410 |
| <a name="l00411"></a>00411 <span class="keywordflow">do</span> |
| <a name="l00412"></a>00412 { |
| <a name="l00413"></a>00413 <span class="comment">/* Calculating Y4(1) to Y4(N-1) from Y2 using equation Y4(k) = Y2(k) - Y4(k-1) */</span> |
| <a name="l00414"></a>00414 <span class="comment">/* pState pointer (pS1) is incremented twice as the real values are located alternatively in the array */</span> |
| <a name="l00415"></a>00415 in = *pS1++ - in; |
| <a name="l00416"></a>00416 *pbuff++ = in; |
| <a name="l00417"></a>00417 <span class="comment">/* points to the next real value */</span> |
| <a name="l00418"></a>00418 pS1++; |
| <a name="l00419"></a>00419 |
| <a name="l00420"></a>00420 |
| <a name="l00421"></a>00421 <span class="comment">/* Decrement the loop counter */</span> |
| <a name="l00422"></a>00422 i--; |
| <a name="l00423"></a>00423 } <span class="keywordflow">while</span>(i > 0u); |
| <a name="l00424"></a>00424 |
| <a name="l00425"></a>00425 |
| <a name="l00426"></a>00426 <span class="comment">/*------------ Normalizing the output by multiplying with the normalizing factor ----------*/</span> |
| <a name="l00427"></a>00427 |
| <a name="l00428"></a>00428 <span class="comment">/* Initializing the loop counter */</span> |
| <a name="l00429"></a>00429 i = (uint32_t) S->N; |
| <a name="l00430"></a>00430 |
| <a name="l00431"></a>00431 <span class="comment">/* pbuff initialized to the pInlineBuffer(now contains the output values) */</span> |
| <a name="l00432"></a>00432 pbuff = pInlineBuffer; |
| <a name="l00433"></a>00433 |
| <a name="l00434"></a>00434 <span class="keywordflow">do</span> |
| <a name="l00435"></a>00435 { |
| <a name="l00436"></a>00436 <span class="comment">/* Multiplying pInlineBuffer with the normalizing factor sqrt(2/N) */</span> |
| <a name="l00437"></a>00437 in = *pbuff; |
| <a name="l00438"></a>00438 *pbuff++ = in * S->normalize; |
| <a name="l00439"></a>00439 |
| <a name="l00440"></a>00440 <span class="comment">/* Decrement the loop counter */</span> |
| <a name="l00441"></a>00441 i--; |
| <a name="l00442"></a>00442 } <span class="keywordflow">while</span>(i > 0u); |
| <a name="l00443"></a>00443 |
| <a name="l00444"></a>00444 <span class="preprocessor">#endif </span><span class="comment">/* #ifndef ARM_MATH_CM0 */</span> |
| <a name="l00445"></a>00445 |
| <a name="l00446"></a>00446 } |
| <a name="l00447"></a>00447 |
| </pre></div></div> |
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