blob: 6ab41e5bfa30c3bef85a289f508d237b5a3799de [file] [log] [blame]
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/>
<title>CMSIS DSP Software Library: Real FFT Functions</title>
<link href="tabs.css" rel="stylesheet" type="text/css"/>
<link href="search/search.css" rel="stylesheet" type="text/css"/>
<script type="text/javaScript" src="search/search.js"></script>
<link href="doxygen.css" rel="stylesheet" type="text/css"/>
</head>
<body onload='searchBox.OnSelectItem(0);'>
<!-- Generated by Doxygen 1.7.2 -->
<script type="text/javascript"><!--
var searchBox = new SearchBox("searchBox", "search",false,'Search');
--></script>
<div class="navigation" id="top">
<div class="tabs">
<ul class="tablist">
<li><a href="index.html"><span>Main&#160;Page</span></a></li>
<li><a href="modules.html"><span>Modules</span></a></li>
<li><a href="annotated.html"><span>Data&#160;Structures</span></a></li>
<li><a href="files.html"><span>Files</span></a></li>
<li><a href="examples.html"><span>Examples</span></a></li>
<li id="searchli">
<div id="MSearchBox" class="MSearchBoxInactive">
<span class="left">
<img id="MSearchSelect" src="search/mag_sel.png"
onmouseover="return searchBox.OnSearchSelectShow()"
onmouseout="return searchBox.OnSearchSelectHide()"
alt=""/>
<input type="text" id="MSearchField" value="Search" accesskey="S"
onfocus="searchBox.OnSearchFieldFocus(true)"
onblur="searchBox.OnSearchFieldFocus(false)"
onkeyup="searchBox.OnSearchFieldChange(event)"/>
</span><span class="right">
<a id="MSearchClose" href="javascript:searchBox.CloseResultsWindow()"><img id="MSearchCloseImg" border="0" src="search/close.png" alt=""/></a>
</span>
</div>
</li>
</ul>
</div>
</div>
<div class="header">
<div class="summary">
<a href="#func-members">Functions</a> &#124;
<a href="#var-members">Variables</a> </div>
<div class="headertitle">
<h1>Real FFT Functions<br/>
<small>
[<a class="el" href="group__group_transforms.html">Transform Functions</a>]</small>
</h1> </div>
</div>
<div class="contents">
<table class="memberdecls">
<tr><td colspan="2"><h2><a name="func-members"></a>
Functions</h2></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___r_f_f_t___r_i_f_f_t.html#ga10717ee326bf50832ef1c25b85a23068">arm_rfft_init_f32</a> (<a class="el" href="structarm__rfft__instance__f32.html">arm_rfft_instance_f32</a> *S, <a class="el" href="structarm__cfft__radix4__instance__f32.html">arm_cfft_radix4_instance_f32</a> *S_CFFT, uint32_t fftLenReal, uint32_t ifftFlagR, uint32_t bitReverseFlag)</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___r_f_f_t___r_i_f_f_t.html#ga3df1766d230532bc068fc4ed69d0fcdc">arm_rfft_f32</a> (const <a class="el" href="structarm__rfft__instance__f32.html">arm_rfft_instance_f32</a> *S, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *pSrc, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *pDst)</td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___r_f_f_t___r_i_f_f_t.html#ga8b9c7f99f3c368c82048cd1899acbbd5">arm_rfft_init_q31</a> (<a class="el" href="structarm__rfft__instance__q31.html">arm_rfft_instance_q31</a> *S, <a class="el" href="structarm__cfft__radix4__instance__q31.html">arm_cfft_radix4_instance_q31</a> *S_CFFT, uint32_t fftLenReal, uint32_t ifftFlagR, uint32_t bitReverseFlag)</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___r_f_f_t___r_i_f_f_t.html#gabaeab5646aeea9844e6d42ca8c73fe3a">arm_rfft_q31</a> (const <a class="el" href="structarm__rfft__instance__q31.html">arm_rfft_instance_q31</a> *S, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *pSrc, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *pDst)</td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___r_f_f_t___r_i_f_f_t.html#ga2530ebf44b7f5b559b191ff7265a9120">arm_rfft_init_q15</a> (<a class="el" href="structarm__rfft__instance__q15.html">arm_rfft_instance_q15</a> *S, <a class="el" href="structarm__cfft__radix4__instance__q15.html">arm_cfft_radix4_instance_q15</a> *S_CFFT, uint32_t fftLenReal, uint32_t ifftFlagR, uint32_t bitReverseFlag)</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___r_f_f_t___r_i_f_f_t.html#ga00e615f5db21736ad5b27fb6146f3fc5">arm_rfft_q15</a> (const <a class="el" href="structarm__rfft__instance__q15.html">arm_rfft_instance_q15</a> *S, <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *pSrc, <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *pDst)</td></tr>
<tr><td colspan="2"><h2><a name="var-members"></a>
Variables</h2></td></tr>
<tr><td class="memItemLeft" align="right" valign="top">static const <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___r_f_f_t___r_i_f_f_t.html#gaae653673880e55a10f8b11823e0911b7">realCoefA</a> [2048]</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">static const <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___r_f_f_t___r_i_f_f_t.html#ga848be13f6359b0dfe02e77aecd74cf2e">realCoefB</a> [2048]</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">const <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___r_f_f_t___r_i_f_f_t.html#gacebced5a9d92f1913a0afe2adef7a886">realCoefAQ31</a> [1024]</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">const <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___r_f_f_t___r_i_f_f_t.html#gaa3baee87ab9cc94a81d63135a004a3be">realCoefBQ31</a> [1024]</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">static const <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___r_f_f_t___r_i_f_f_t.html#gabb599b7817b377892d3674931849a5f1">realCoefAQ15</a> [2048]</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">static const <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___r_f_f_t___r_i_f_f_t.html#ga07c39dddf1799f8394533710fb9e17b0">realCoefBQ15</a> [2048]</td></tr>
</table>
<hr/><a name="_details"></a><h2>Detailed Description</h2>
<dl class="user"><dt><b></b></dt><dd>Complex FFT/IFFT typically assumes complex input and output. However many applications use real valued data in time domain. Real FFT/IFFT efficiently process real valued sequences with the advantage of requirement of low memory and with less complexity.</dd></dl>
<dl class="user"><dt><b></b></dt><dd>This set of functions implements Real Fast Fourier Transforms(RFFT) and Real Inverse Fast Fourier Transform(RIFFT) for Q15, Q31, and floating-point data types.</dd></dl>
<dl class="user"><dt><b>Algorithm: </b></dt><dd></dd></dl>
<p><b>Real Fast Fourier Transform:</b> </p>
<dl class="user"><dt><b></b></dt><dd>Real FFT of N-point is calculated using CFFT of N/2-point and Split RFFT process as shown below figure. </dd></dl>
<dl class="user"><dt><b></b></dt><dd><div align="center">
<img src="RFFT.gif" alt="RFFT.gif"/>
<p><strong>Real Fast Fourier Transform</strong></p></div>
</dd></dl>
<dl class="user"><dt><b></b></dt><dd>The RFFT functions operate on blocks of input and output data and each call to the function processes <code>fftLenR</code> samples through the transform. <code>pSrc</code> points to input array containing <code>fftLenR</code> values. <code>pDst</code> points to output array containing <code>2*fftLenR</code> values. <br/>
Input for real FFT is in the order of <pre>{real[0], real[1], real[2], real[3], ..}</pre> Output for real FFT is complex and are in the order of <pre>{real(0), imag(0), real(1), imag(1), ...}</pre></dd></dl>
<p><b>Real Inverse Fast Fourier Transform:</b> </p>
<dl class="user"><dt><b></b></dt><dd>Real IFFT of N-point is calculated using Split RIFFT process and CFFT of N/2-point as shown below figure. </dd></dl>
<dl class="user"><dt><b></b></dt><dd><div align="center">
<img src="RIFFT.gif" alt="RIFFT.gif"/>
<p><strong>Real Inverse Fast Fourier Transform</strong></p></div>
</dd></dl>
<dl class="user"><dt><b></b></dt><dd>The RIFFT functions operate on blocks of input and output data and each call to the function processes <code>2*fftLenR</code> samples through the transform. <code>pSrc</code> points to input array containing <code>2*fftLenR</code> values. <code>pDst</code> points to output array containing <code>fftLenR</code> values. <br/>
Input for real IFFT is complex and are in the order of <pre>{real(0), imag(0), real(1), imag(1), ...}</pre> Output for real IFFT is real and in the order of <pre>{real[0], real[1], real[2], real[3], ..}</pre></dd></dl>
<dl class="user"><dt><b>Lengths supported by the transform: </b></dt><dd></dd></dl>
<dl class="user"><dt><b></b></dt><dd>Real FFT/IFFT supports the lengths [128, 512, 2048], as it internally uses CFFT/CIFFT.</dd></dl>
<dl class="user"><dt><b>Instance Structure </b></dt><dd>A separate instance structure must be defined for each Instance but the twiddle factors can be reused. There are separate instance structure declarations for each of the 3 supported data types.</dd></dl>
<dl class="user"><dt><b>Initialization Functions </b></dt><dd>There is also an associated initialization function for each data type. The initialization function performs the following operations:<ul>
<li>Sets the values of the internal structure fields.</li>
<li>Initializes twiddle factor tables.</li>
<li>Initializes CFFT data structure fields. </li>
</ul>
</dd></dl>
<dl class="user"><dt><b></b></dt><dd>Use of the initialization function is optional. However, if the initialization function is used, then the instance structure cannot be placed into a const data section. To place an instance structure into a const data section, the instance structure must be manually initialized. Manually initialize the instance structure as follows: <pre>
<a class="el" href="structarm__rfft__instance__f32.html" title="Instance structure for the floating-point RFFT/RIFFT function.">arm_rfft_instance_f32</a> S = {fftLenReal, fftLenBy2, ifftFlagR, bitReverseFlagR, twidCoefRModifier, pTwiddleAReal, pTwiddleBReal, pCfft};
<a class="el" href="structarm__rfft__instance__q31.html" title="Instance structure for the Q31 RFFT/RIFFT function.">arm_rfft_instance_q31</a> S = {fftLenReal, fftLenBy2, ifftFlagR, bitReverseFlagR, twidCoefRModifier, pTwiddleAReal, pTwiddleBReal, pCfft};
<a class="el" href="structarm__rfft__instance__q15.html" title="Instance structure for the Q15 RFFT/RIFFT function.">arm_rfft_instance_q15</a> S = {fftLenReal, fftLenBy2, ifftFlagR, bitReverseFlagR, twidCoefRModifier, pTwiddleAReal, pTwiddleBReal, pCfft};
</pre> where <code>fftLenReal</code> length of RFFT/RIFFT; <code>fftLenBy2</code> length of CFFT/CIFFT. <code>ifftFlagR</code> Flag for selection of RFFT or RIFFT(Set ifftFlagR to calculate RIFFT otherwise calculates RFFT); <code>bitReverseFlagR</code> Flag for selection of output order(Set bitReverseFlagR to output in normal order otherwise output in bit reversed order); <code>twidCoefRModifier</code> modifier for twiddle factor table which supports 128, 512, 2048 RFFT lengths with same table; <code>pTwiddleAReal</code>points to A array of twiddle coefficients; <code>pTwiddleBReal</code>points to B array of twiddle coefficients; <code>pCfft</code> points to the CFFT Instance structure. The CFFT structure also needs to be initialized, refer to <a class="el" href="group___c_f_f_t___c_i_f_f_t.html#ga521f670cd9c571bc61aff9bec89f4c26" title="Processing function for the floating-point CFFT/CIFFT.">arm_cfft_radix4_f32()</a> for details regarding static initialization of cfft structure.</dd></dl>
<dl class="user"><dt><b>Fixed-Point Behavior </b></dt><dd>Care must be taken when using the fixed-point versions of the RFFT/RIFFT function. Refer to the function specific documentation below for usage guidelines. </dd></dl>
<hr/><h2>Function Documentation</h2>
<a class="anchor" id="ga10717ee326bf50832ef1c25b85a23068"></a><!-- doxytag: member="arm_rfft_init_f32.c::arm_rfft_init_f32" ref="ga10717ee326bf50832ef1c25b85a23068" args="(arm_rfft_instance_f32 *S, arm_cfft_radix4_instance_f32 *S_CFFT, uint32_t fftLenReal, uint32_t ifftFlagR, uint32_t bitReverseFlag)" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a> arm_rfft_init_f32 </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structarm__rfft__instance__f32.html">arm_rfft_instance_f32</a> *&#160;</td>
<td class="paramname"> <em>S</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="structarm__cfft__radix4__instance__f32.html">arm_cfft_radix4_instance_f32</a> *&#160;</td>
<td class="paramname"> <em>S_CFFT</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t&#160;</td>
<td class="paramname"> <em>fftLenReal</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t&#160;</td>
<td class="paramname"> <em>ifftFlagR</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t&#160;</td>
<td class="paramname"> <em>bitReverseFlag</em>&#160;</td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>Initialization function for the floating-point RFFT/RIFFT. </p>
<dl><dt><b>Parameters:</b></dt><dd>
<table class="params">
<tr><td class="paramdir">[in,out]</td><td class="paramname">*S</td><td>points to an instance of the floating-point RFFT/RIFFT structure. </td></tr>
<tr><td class="paramdir">[in,out]</td><td class="paramname">*S_CFFT</td><td>points to an instance of the floating-point CFFT/CIFFT structure. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">fftLenReal</td><td>length of the FFT. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">ifftFlagR</td><td>flag that selects forward (ifftFlagR=0) or inverse (ifftFlagR=1) transform. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">bitReverseFlag</td><td>flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output. </td></tr>
</table>
</dd>
</dl>
<dl class="return"><dt><b>Returns:</b></dt><dd>The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if <code>fftLenReal</code> is not a supported value.</dd></dl>
<dl class="user"><dt><b>Description: </b></dt><dd></dd></dl>
<dl class="user"><dt><b></b></dt><dd>The parameter <code>fftLenReal</code> Specifies length of RFFT/RIFFT Process. Supported FFT Lengths are 128, 512, 2048. </dd></dl>
<dl class="user"><dt><b></b></dt><dd>The parameter <code>ifftFlagR</code> controls whether a forward or inverse transform is computed. Set(=1) ifftFlagR to calculate RIFFT, otherwise RFFT is calculated. </dd></dl>
<dl class="user"><dt><b></b></dt><dd>The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order. Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order. </dd></dl>
<dl class="user"><dt><b></b></dt><dd>This function also initializes Twiddle factor table. </dd></dl>
<p>Definition at line <a class="el" href="arm__rfft__init__f32_8c_source.html#l01638">1638</a> of file <a class="el" href="arm__rfft__init__f32_8c_source.html">arm_rfft_init_f32.c</a>.</p>
</div>
</div>
<a class="anchor" id="ga3df1766d230532bc068fc4ed69d0fcdc"></a><!-- doxytag: member="arm_rfft_f32.c::arm_rfft_f32" ref="ga3df1766d230532bc068fc4ed69d0fcdc" args="(const arm_rfft_instance_f32 *S, float32_t *pSrc, float32_t *pDst)" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">void arm_rfft_f32 </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="structarm__rfft__instance__f32.html">arm_rfft_instance_f32</a> *&#160;</td>
<td class="paramname"> <em>S</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *&#160;</td>
<td class="paramname"> <em>pSrc</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *&#160;</td>
<td class="paramname"> <em>pDst</em>&#160;</td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>Processing function for the floating-point RFFT/RIFFT. </p>
<dl><dt><b>Parameters:</b></dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">*S</td><td>points to an instance of the floating-point RFFT/RIFFT structure. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">*pSrc</td><td>points to the input buffer. </td></tr>
<tr><td class="paramdir">[out]</td><td class="paramname">*pDst</td><td>points to the output buffer. </td></tr>
</table>
</dd>
</dl>
<dl class="return"><dt><b>Returns:</b></dt><dd>none. </dd></dl>
<p>Definition at line <a class="el" href="arm__rfft__f32_8c_source.html#l00150">150</a> of file <a class="el" href="arm__rfft__f32_8c_source.html">arm_rfft_f32.c</a>.</p>
</div>
</div>
<a class="anchor" id="ga8b9c7f99f3c368c82048cd1899acbbd5"></a><!-- doxytag: member="arm_rfft_init_q31.c::arm_rfft_init_q31" ref="ga8b9c7f99f3c368c82048cd1899acbbd5" args="(arm_rfft_instance_q31 *S, arm_cfft_radix4_instance_q31 *S_CFFT, uint32_t fftLenReal, uint32_t ifftFlagR, uint32_t bitReverseFlag)" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a> arm_rfft_init_q31 </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structarm__rfft__instance__q31.html">arm_rfft_instance_q31</a> *&#160;</td>
<td class="paramname"> <em>S</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="structarm__cfft__radix4__instance__q31.html">arm_cfft_radix4_instance_q31</a> *&#160;</td>
<td class="paramname"> <em>S_CFFT</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t&#160;</td>
<td class="paramname"> <em>fftLenReal</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t&#160;</td>
<td class="paramname"> <em>ifftFlagR</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t&#160;</td>
<td class="paramname"> <em>bitReverseFlag</em>&#160;</td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>Initialization function for the Q31 RFFT/RIFFT. </p>
<dl><dt><b>Parameters:</b></dt><dd>
<table class="params">
<tr><td class="paramdir">[in,out]</td><td class="paramname">*S</td><td>points to an instance of the Q31 RFFT/RIFFT structure. </td></tr>
<tr><td class="paramdir">[in,out]</td><td class="paramname">*S_CFFT</td><td>points to an instance of the Q31 CFFT/CIFFT structure. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">fftLenReal</td><td>length of the FFT. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">ifftFlagR</td><td>flag that selects forward (ifftFlagR=0) or inverse (ifftFlagR=1) transform. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">bitReverseFlag</td><td>flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output. </td></tr>
</table>
</dd>
</dl>
<dl class="return"><dt><b>Returns:</b></dt><dd>The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if <code>fftLenReal</code> is not a supported value.</dd></dl>
<dl class="user"><dt><b>Description: </b></dt><dd></dd></dl>
<dl class="user"><dt><b></b></dt><dd>The parameter <code>fftLenReal</code> Specifies length of RFFT/RIFFT Process. Supported FFT Lengths are 128, 512, 2048. </dd></dl>
<dl class="user"><dt><b></b></dt><dd>The parameter <code>ifftFlagR</code> controls whether a forward or inverse transform is computed. Set(=1) ifftFlagR to calculate RIFFT, otherwise RFFT is calculated. </dd></dl>
<dl class="user"><dt><b></b></dt><dd>The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order. Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order. </dd></dl>
<dl class="user"><dt><b></b></dt><dd>This function also initializes Twiddle factor table. </dd></dl>
<p>Definition at line <a class="el" href="arm__rfft__init__q31_8c_source.html#l00617">617</a> of file <a class="el" href="arm__rfft__init__q31_8c_source.html">arm_rfft_init_q31.c</a>.</p>
</div>
</div>
<a class="anchor" id="gabaeab5646aeea9844e6d42ca8c73fe3a"></a><!-- doxytag: member="arm_rfft_q31.c::arm_rfft_q31" ref="gabaeab5646aeea9844e6d42ca8c73fe3a" args="(const arm_rfft_instance_q31 *S, q31_t *pSrc, q31_t *pDst)" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">void arm_rfft_q31 </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="structarm__rfft__instance__q31.html">arm_rfft_instance_q31</a> *&#160;</td>
<td class="paramname"> <em>S</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *&#160;</td>
<td class="paramname"> <em>pSrc</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *&#160;</td>
<td class="paramname"> <em>pDst</em>&#160;</td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>Processing function for the Q31 RFFT/RIFFT. </p>
<dl><dt><b>Parameters:</b></dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">*S</td><td>points to an instance of the Q31 RFFT/RIFFT structure. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">*pSrc</td><td>points to the input buffer. </td></tr>
<tr><td class="paramdir">[out]</td><td class="paramname">*pDst</td><td>points to the output buffer. </td></tr>
</table>
</dd>
</dl>
<dl class="return"><dt><b>Returns:</b></dt><dd>none.</dd></dl>
<dl class="user"><dt><b>Input an output formats: </b></dt><dd></dd></dl>
<dl class="user"><dt><b></b></dt><dd>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: </dd></dl>
<dl class="user"><dt><b></b></dt><dd><div align="center">
<img src="RFFTQ31.gif" alt="RFFTQ31.gif"/>
<p><strong>Input and Output Formats for Q31 RFFT</strong></p></div>
</dd></dl>
<dl class="user"><dt><b></b></dt><dd><div align="center">
<img src="RIFFTQ31.gif" alt="RIFFTQ31.gif"/>
<p><strong>Input and Output Formats for Q31 RIFFT</strong></p></div>
</dd></dl>
<p>Definition at line <a class="el" href="arm__rfft__q31_8c_source.html#l00080">80</a> of file <a class="el" href="arm__rfft__q31_8c_source.html">arm_rfft_q31.c</a>.</p>
</div>
</div>
<a class="anchor" id="ga2530ebf44b7f5b559b191ff7265a9120"></a><!-- doxytag: member="arm_rfft_init_q15.c::arm_rfft_init_q15" ref="ga2530ebf44b7f5b559b191ff7265a9120" args="(arm_rfft_instance_q15 *S, arm_cfft_radix4_instance_q15 *S_CFFT, uint32_t fftLenReal, uint32_t ifftFlagR, uint32_t bitReverseFlag)" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname"><a class="el" href="arm__math_8h.html#a5e459c6409dfcd2927bb8a57491d7cf6">arm_status</a> arm_rfft_init_q15 </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structarm__rfft__instance__q15.html">arm_rfft_instance_q15</a> *&#160;</td>
<td class="paramname"> <em>S</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="structarm__cfft__radix4__instance__q15.html">arm_cfft_radix4_instance_q15</a> *&#160;</td>
<td class="paramname"> <em>S_CFFT</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t&#160;</td>
<td class="paramname"> <em>fftLenReal</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t&#160;</td>
<td class="paramname"> <em>ifftFlagR</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t&#160;</td>
<td class="paramname"> <em>bitReverseFlag</em>&#160;</td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>Initialization function for the Q15 RFFT/RIFFT. </p>
<dl><dt><b>Parameters:</b></dt><dd>
<table class="params">
<tr><td class="paramdir">[in,out]</td><td class="paramname">*S</td><td>points to an instance of the Q15 RFFT/RIFFT structure. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">*S_CFFT</td><td>points to an instance of the Q15 CFFT/CIFFT structure. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">fftLenReal</td><td>length of the FFT. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">ifftFlagR</td><td>flag that selects forward (ifftFlagR=0) or inverse (ifftFlagR=1) transform. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">bitReverseFlag</td><td>flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output. </td></tr>
</table>
</dd>
</dl>
<dl class="return"><dt><b>Returns:</b></dt><dd>The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if <code>fftLenReal</code> is not a supported value.</dd></dl>
<dl class="user"><dt><b>Description: </b></dt><dd></dd></dl>
<dl class="user"><dt><b></b></dt><dd>The parameter <code>fftLenReal</code> Specifies length of RFFT/RIFFT Process. Supported FFT Lengths are 128, 512, 2048. </dd></dl>
<dl class="user"><dt><b></b></dt><dd>The parameter <code>ifftFlagR</code> controls whether a forward or inverse transform is computed. Set(=1) ifftFlagR to calculate RIFFT, otherwise RFFT is calculated. </dd></dl>
<dl class="user"><dt><b></b></dt><dd>The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order. Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order. </dd></dl>
<dl class="user"><dt><b></b></dt><dd>This function also initializes Twiddle factor table. </dd></dl>
<p>Definition at line <a class="el" href="arm__rfft__init__q15_8c_source.html#l00620">620</a> of file <a class="el" href="arm__rfft__init__q15_8c_source.html">arm_rfft_init_q15.c</a>.</p>
</div>
</div>
<a class="anchor" id="ga00e615f5db21736ad5b27fb6146f3fc5"></a><!-- doxytag: member="arm_rfft_q15.c::arm_rfft_q15" ref="ga00e615f5db21736ad5b27fb6146f3fc5" args="(const arm_rfft_instance_q15 *S, q15_t *pSrc, q15_t *pDst)" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">void arm_rfft_q15 </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="structarm__rfft__instance__q15.html">arm_rfft_instance_q15</a> *&#160;</td>
<td class="paramname"> <em>S</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *&#160;</td>
<td class="paramname"> <em>pSrc</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *&#160;</td>
<td class="paramname"> <em>pDst</em>&#160;</td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>Processing function for the Q15 RFFT/RIFFT. </p>
<dl><dt><b>Parameters:</b></dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">*S</td><td>points to an instance of the Q15 RFFT/RIFFT structure. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">*pSrc</td><td>points to the input buffer. </td></tr>
<tr><td class="paramdir">[out]</td><td class="paramname">*pDst</td><td>points to the output buffer. </td></tr>
</table>
</dd>
</dl>
<dl class="return"><dt><b>Returns:</b></dt><dd>none.</dd></dl>
<dl class="user"><dt><b>Input an output formats: </b></dt><dd></dd></dl>
<dl class="user"><dt><b></b></dt><dd>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: </dd></dl>
<dl class="user"><dt><b></b></dt><dd><div align="center">
<img src="RFFTQ15.gif" alt="RFFTQ15.gif"/>
<p><strong>Input and Output Formats for Q15 RFFT</strong></p></div>
</dd></dl>
<dl class="user"><dt><b></b></dt><dd><div align="center">
<img src="RIFFTQ15.gif" alt="RIFFTQ15.gif"/>
<p><strong>Input and Output Formats for Q15 RIFFT</strong></p></div>
</dd></dl>
<p>Definition at line <a class="el" href="arm__rfft__q15_8c_source.html#l00080">80</a> of file <a class="el" href="arm__rfft__q15_8c_source.html">arm_rfft_q15.c</a>.</p>
</div>
</div>
<hr/><h2>Variable Documentation</h2>
<a class="anchor" id="gaae653673880e55a10f8b11823e0911b7"></a><!-- doxytag: member="arm_rfft_init_f32.c::realCoefA" ref="gaae653673880e55a10f8b11823e0911b7" args="[2048]" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">const <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> <a class="el" href="group___r_f_f_t___r_i_f_f_t.html#gaae653673880e55a10f8b11823e0911b7">realCoefA</a>[2048]<code> [static]</code></td>
</tr>
</table>
</div>
<div class="memdoc">
<dl class="user"><dt><b></b></dt><dd>Generation of realCoefA array: </dd></dl>
<dl class="user"><dt><b></b></dt><dd>n = 1024 <pre>for (i = 0; i &lt; n; i++)
{
pATable[2 * i] = 0.5 * (1.0 - sin (2 * PI / (double) (2 * n) * (double) i));
pATable[2 * i + 1] = 0.5 * (-1.0 * cos (2 * PI / (double) (2 * n) * (double) i));
} </pre> </dd></dl>
<p>Definition at line <a class="el" href="arm__rfft__init__f32_8c_source.html#l00059">59</a> of file <a class="el" href="arm__rfft__init__f32_8c_source.html">arm_rfft_init_f32.c</a>.</p>
</div>
</div>
<a class="anchor" id="ga848be13f6359b0dfe02e77aecd74cf2e"></a><!-- doxytag: member="arm_rfft_init_f32.c::realCoefB" ref="ga848be13f6359b0dfe02e77aecd74cf2e" args="[2048]" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">const <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> <a class="el" href="group___r_f_f_t___r_i_f_f_t.html#ga848be13f6359b0dfe02e77aecd74cf2e">realCoefB</a>[2048]<code> [static]</code></td>
</tr>
</table>
</div>
<div class="memdoc">
<dl class="user"><dt><b></b></dt><dd>Generation of realCoefB array: </dd></dl>
<dl class="user"><dt><b></b></dt><dd>n = 1024 <pre>for (i = 0; i &lt; n; i++)
{
pBTable[2 * i] = 0.5 * (1.0 + sin (2 * PI / (double) (2 * n) * (double) i));
pBTable[2 * i + 1] = 0.5 * (1.0 * cos (2 * PI / (double) (2 * n) * (double) i));
} </pre> </dd></dl>
<p>Definition at line <a class="el" href="arm__rfft__init__f32_8c_source.html#l00843">843</a> of file <a class="el" href="arm__rfft__init__f32_8c_source.html">arm_rfft_init_f32.c</a>.</p>
</div>
</div>
<a class="anchor" id="gacebced5a9d92f1913a0afe2adef7a886"></a><!-- doxytag: member="arm_rfft_init_q31.c::realCoefAQ31" ref="gacebced5a9d92f1913a0afe2adef7a886" args="[1024]" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">const <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> <a class="el" href="group___r_f_f_t___r_i_f_f_t.html#gacebced5a9d92f1913a0afe2adef7a886">realCoefAQ31</a>[1024]</td>
</tr>
</table>
</div>
<div class="memdoc">
<dl class="user"><dt><b></b></dt><dd>Generation floating point realCoefAQ31 array: </dd></dl>
<dl class="user"><dt><b></b></dt><dd>n = 1024 <pre>for (i = 0; i &lt; n; i++)
{
pATable[2 * i] = 0.5 * (1.0 - sin (2 * PI / (double) (2 * n) * (double) i));
pATable[2 * i + 1] = 0.5 * (-1.0 * cos (2 * PI / (double) (2 * n) * (double) i));
}</pre> </dd></dl>
<dl class="user"><dt><b></b></dt><dd>Convert to fixed point Q31 format round(pATable[i] * pow(2, 31)) </dd></dl>
<p>Definition at line <a class="el" href="arm__rfft__init__q31_8c_source.html#l00060">60</a> of file <a class="el" href="arm__rfft__init__q31_8c_source.html">arm_rfft_init_q31.c</a>.</p>
</div>
</div>
<a class="anchor" id="gaa3baee87ab9cc94a81d63135a004a3be"></a><!-- doxytag: member="arm_rfft_init_q31.c::realCoefBQ31" ref="gaa3baee87ab9cc94a81d63135a004a3be" args="[1024]" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">const <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> <a class="el" href="group___r_f_f_t___r_i_f_f_t.html#gaa3baee87ab9cc94a81d63135a004a3be">realCoefBQ31</a>[1024]</td>
</tr>
</table>
</div>
<div class="memdoc">
<dl class="user"><dt><b></b></dt><dd>Generation of realCoefBQ31 array: </dd></dl>
<dl class="user"><dt><b></b></dt><dd>n = 512 <pre>for (i = 0; i &lt; n; i++)
{
pBTable[2 * i] = 0.5 * (1.0 + sin (2 * PI / (double) (2 * n) * (double) i));
pBTable[2 * i + 1] = 0.5 * (1.0 * cos (2 * PI / (double) (2 * n) * (double) i));
} </pre> </dd></dl>
<dl class="user"><dt><b></b></dt><dd>Convert to fixed point Q31 format round(pBTable[i] * pow(2, 31)) </dd></dl>
<p>Definition at line <a class="el" href="arm__rfft__init__q31_8c_source.html#l00336">336</a> of file <a class="el" href="arm__rfft__init__q31_8c_source.html">arm_rfft_init_q31.c</a>.</p>
</div>
</div>
<a class="anchor" id="gabb599b7817b377892d3674931849a5f1"></a><!-- doxytag: member="arm_rfft_init_q15.c::realCoefAQ15" ref="gabb599b7817b377892d3674931849a5f1" args="[2048]" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">const <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> <a class="el" href="group___r_f_f_t___r_i_f_f_t.html#gabb599b7817b377892d3674931849a5f1">realCoefAQ15</a>[2048]<code> [static]</code></td>
</tr>
</table>
</div>
<div class="memdoc">
<dl class="user"><dt><b></b></dt><dd>Generation floating point real_CoefA array: </dd></dl>
<dl class="user"><dt><b></b></dt><dd>n = 1024 <pre>for (i = 0; i &lt; n; i++)
{
pATable[2 * i] = 0.5 * (1.0 - sin (2 * PI / (double) (2 * n) * (double) i));
pATable[2 * i + 1] = 0.5 * (-1.0 * cos (2 * PI / (double) (2 * n) * (double) i));
} </pre> </dd></dl>
<dl class="user"><dt><b></b></dt><dd>Convert to fixed point Q15 format round(pATable[i] * pow(2, 15)) </dd></dl>
<p>Definition at line <a class="el" href="arm__rfft__init__q15_8c_source.html#l00063">63</a> of file <a class="el" href="arm__rfft__init__q15_8c_source.html">arm_rfft_init_q15.c</a>.</p>
</div>
</div>
<a class="anchor" id="ga07c39dddf1799f8394533710fb9e17b0"></a><!-- doxytag: member="arm_rfft_init_q15.c::realCoefBQ15" ref="ga07c39dddf1799f8394533710fb9e17b0" args="[2048]" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">const <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> <a class="el" href="group___r_f_f_t___r_i_f_f_t.html#ga07c39dddf1799f8394533710fb9e17b0">realCoefBQ15</a>[2048]<code> [static]</code></td>
</tr>
</table>
</div>
<div class="memdoc">
<dl class="user"><dt><b></b></dt><dd>Generation of real_CoefB array: </dd></dl>
<dl class="user"><dt><b></b></dt><dd>n = 1024 <pre>for (i = 0; i &lt; n; i++)
{
pBTable[2 * i] = 0.5 * (1.0 + sin (2 * PI / (double) (2 * n) * (double) i));
pBTable[2 * i + 1] = 0.5 * (1.0 * cos (2 * PI / (double) (2 * n) * (double) i));
} </pre> </dd></dl>
<dl class="user"><dt><b></b></dt><dd>Convert to fixed point Q15 format round(pBTable[i] * pow(2, 15)) </dd></dl>
<p>Definition at line <a class="el" href="arm__rfft__init__q15_8c_source.html#l00339">339</a> of file <a class="el" href="arm__rfft__init__q15_8c_source.html">arm_rfft_init_q15.c</a>.</p>
</div>
</div>
</div>
<!--- window showing the filter options -->
<div id="MSearchSelectWindow"
onmouseover="return searchBox.OnSearchSelectShow()"
onmouseout="return searchBox.OnSearchSelectHide()"
onkeydown="return searchBox.OnSearchSelectKey(event)">
<a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(0)"><span class="SelectionMark">&#160;</span>All</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(1)"><span class="SelectionMark">&#160;</span>Data Structures</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(2)"><span class="SelectionMark">&#160;</span>Files</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(3)"><span class="SelectionMark">&#160;</span>Functions</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(4)"><span class="SelectionMark">&#160;</span>Variables</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(5)"><span class="SelectionMark">&#160;</span>Typedefs</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(6)"><span class="SelectionMark">&#160;</span>Enumerations</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(7)"><span class="SelectionMark">&#160;</span>Enumerator</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(8)"><span class="SelectionMark">&#160;</span>Defines</a></div>
<!-- iframe showing the search results (closed by default) -->
<div id="MSearchResultsWindow">
<iframe src="" frameborder="0"
name="MSearchResults" id="MSearchResults">
</iframe>
</div>
<hr class="footer"/><address class="footer"><small>Generated on Fri Jul 15 2011 13:16:21 for CMSIS DSP Software Library by&#160;
<a href="http://www.doxygen.org/index.html">
<img class="footer" src="doxygen.png" alt="doxygen"/></a> 1.7.2 </small></address>
</body>
</html>