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/* * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved. * * Use of this source code is governed by a BSD-style license * that can be found in the LICENSE file in the root of the source * tree. An additional intellectual property rights grant can be found * in the file PATENTS. All contributing project authors may * be found in the AUTHORS file in the root of the source tree. */ /* * This file contains the function WebRtcSpl_ComplexFFT(). * The description header can be found in signal_processing_library.h * */ #include "signal_processing_library.h" #define LOG_OUT_OF_MEMORY -100 #define LOG_SIZE_TOO_LARGE -101 // Helper functions static int WebRtcSpl_ComplexIFFTInt(WebRtc_Word16 frfi[], int stages, int mode); static int WebRtcSpl_ComplexFFTInt(WebRtc_Word16 frfi[], int stages, int mode); int WebRtcSpl_ComplexFFT(WebRtc_Word16 frfi[], int stages, int mode) { // Check that stages is a reasonable number if (stages < 0) { return LOG_OUT_OF_MEMORY; } if (stages > 10) { return LOG_SIZE_TOO_LARGE; } // Mode 0: forward FFT if (mode == 0) { return WebRtcSpl_ComplexFFTInt(frfi, stages, mode); } // Mode 1: inverse FFT else { return WebRtcSpl_ComplexIFFTInt(frfi, stages, mode); } } // Forward FFT static int WebRtcSpl_ComplexFFTInt(WebRtc_Word16 frfi[], int stages, int mode) { int i, j, k, m; int l1, l2; int ik, m2; WebRtc_Word16 wr, wi, tawr, tawi; WebRtc_Word32 temp; WebRtc_Word16 *pfrfi; if (stages == 0) { return 0; } // Bit reverse j = 0; pfrfi = &frfi[0]; m2 = 1 << (stages - 1); for (i = 0; i < (m2 - 1); i++) { if (i < j) { temp = (WebRtc_Word32)pfrfi[2 * i]; pfrfi[2 * i] = pfrfi[2 * j]; pfrfi[2 * j] = (WebRtc_Word16)temp; temp = (WebRtc_Word32)pfrfi[2 * i + 1]; pfrfi[2 * i + 1] = pfrfi[2 * j + 1]; pfrfi[2 * j + 1] = (WebRtc_Word16)temp; } k = m2; while (k <= j) { j -= k; k >>= 1; } j += k; } // Loop for each stage l1 = 1; l2 = 2; for (i = 0; i < stages; i++) { pfrfi = &frfi[0]; m2 = l2 >> 1; for (j = 0; j < l1; j++) { wr = WEBRTC_SPL_WORD16_MAX; wi = 0; m = 0; ik = 0; // Loop through first set of butterfly for (k = j; k < (2 * l2); k += l2) { // Butterfly calculations temp = WEBRTC_SPL_MUL_16_16(wr, pfrfi[2 * m2 + ik]) + WEBRTC_SPL_MUL_16_16(wi, pfrfi[2 * m2 + ik + 1]); tawi = (WebRtc_Word16)((temp + 0x4000) >> 15); temp = WEBRTC_SPL_MUL_16_16(wr, pfrfi[2 * m2 + ik + 1]) - WEBRTC_SPL_MUL_16_16(wi, pfrfi[2 * m2 + ik]); tawr = (WebRtc_Word16)((temp + 0x4000) >> 15); temp = WEBRTC_SPL_MUL_16_16(pfrfi[ik], wr) + WEBRTC_SPL_MUL_16_16(pfrfi[ik + 1], wi); pfrfi[2 * m2 + ik + 1] = (WebRtc_Word16)((temp + 0x4000) >> 15); temp = WEBRTC_SPL_MUL_16_16(pfrfi[ik + 1], wr) - WEBRTC_SPL_MUL_16_16(pfrfi[ik], wi); pfrfi[2 * m2 + ik] = (WebRtc_Word16)((temp + 0x4000) >> 15); pfrfi[ik] = (WebRtc_Word16)((WEBRTC_SPL_ADD_SAT_W16(pfrfi[ik], tawr) + 0x1) >> 1); pfrfi[ik + 1] = (WebRtc_Word16)((WEBRTC_SPL_ADD_SAT_W16(pfrfi[ik + 1], tawi) + 0x1) >> 1); // Update trigonometric recurrence tawr = wr; wr = (WebRtc_Word16)((WEBRTC_SPL_ADD_SAT_W16(wr, wr) + 0x1) >> 1); wi = (WebRtc_Word16)((WEBRTC_SPL_SUB_SAT_W16(wi, wi) + 0x1) >> 1); tawi = wi; wi = (WebRtc_Word16)((WEBRTC_SPL_SUB_SAT_W16(tawr, tawi) + 0x1) >> 1); m++; ik += 2; } pfrfi += 2; } l1 = l2; l2 <<= 1; } return 0; } // Inverse FFT static int WebRtcSpl_ComplexIFFTInt(WebRtc_Word16 frfi[], int stages, int mode) { int i, j, k, m; int l1, l2; int ik, m2; WebRtc_Word16 wr, wi, tawr, tawi; WebRtc_Word32 temp; WebRtc_Word16 *pfrfi; if (stages == 0) { return 0; } // Bit reverse j = 0; pfrfi = &frfi[0]; m2 = 1 << (stages - 1); for (i = 0; i < (m2 - 1); i++) { if (i < j) { temp = (WebRtc_Word32)pfrfi[2 * i]; pfrfi[2 * i] = pfrfi[2 * j]; pfrfi[2 * j] = (WebRtc_Word16)temp; temp = (WebRtc_Word32)pfrfi[2 * i + 1]; pfrfi[2 * i + 1] = pfrfi[2 * j + 1]; pfrfi[2 * j + 1] = (WebRtc_Word16)temp; } k = m2; while (k <= j) { j -= k; k >>= 1; } j += k; } // Loop for each stage l1 = 1; l2 = 2; for (i = 0; i < stages; i++) { pfrfi = &frfi[0]; m2 = l2 >> 1; for (j = 0; j < l1; j++) { wr = WEBRTC_SPL_WORD16_MAX; wi = 0; m = 0; ik = 0; // Loop through first set of butterfly for (k = j; k < (2 * l2); k += l2) { // Butterfly calculations temp = WEBRTC_SPL_MUL_16_16(wr, pfrfi[2 * m2 + ik]) + WEBRTC_SPL_MUL_16_16(wi, pfrfi[2 * m2 + ik + 1]); tawi = (WebRtc_Word16)((temp + 0x4000) >> 15); temp = WEBRTC_SPL_MUL_16_16(wr, pfrfi[2 * m2 + ik + 1]) - WEBRTC_SPL_MUL_16_16(wi, pfrfi[2 * m2 + ik]); tawr = (WebRtc_Word16)((temp + 0x4000) >> 15); temp = WEBRTC_SPL_MUL_16_16(pfrfi[ik], wr) + WEBRTC_SPL_MUL_16_16(pfrfi[ik + 1], wi); pfrfi[2 * m2 + ik + 1] = (WebRtc_Word16)((temp + 0x4000) >> 15); temp = WEBRTC_SPL_MUL_16_16(pfrfi[ik + 1], wr) - WEBRTC_SPL_MUL_16_16(pfrfi[ik], wi); pfrfi[2 * m2 + ik] = (WebRtc_Word16)((temp + 0x4000) >> 15); pfrfi[ik] = (WebRtc_Word16)((WEBRTC_SPL_SUB_SAT_W16(pfrfi[ik], tawr) + 0x1) >> 1); pfrfi[ik + 1] = (WebRtc_Word16)((WEBRTC_SPL_SUB_SAT_W16(pfrfi[ik + 1], tawi) + 0x1) >> 1); // Update trigonometric recurrence tawr = wr; wr = (WebRtc_Word16)((WEBRTC_SPL_ADD_SAT_W16(wr, wr) + 0x1) >> 1); wi = (WebRtc_Word16)((WEBRTC_SPL_SUB_SAT_W16(wi, wi) + 0x1) >> 1); tawi = wi; wi = (WebRtc_Word16)((WEBRTC_SPL_SUB_SAT_W16(tawr, tawi) + 0x1) >> 1); m++; ik += 2; } pfrfi += 2; } l1 = l2; l2 <<= 1; } return 0; }