commit af3dce75e5423fb7d057dfea4ea6865adf8101c2
author Jakub Pawlowski <jpawlowski@google.com> Wed Oct 06 00:39:29 2021 +0200
committer Jakub Pawlowski <jpawlowski@google.com> Wed Oct 06 10:11:10 2021 +0200
tree 2d65b273d4ea12fb5baad4454e963858e9e461f6
parent 1932ece14a90b61b589fe19bc18d07dae95258ba

Use FFT for LC3

Bug: 150670922
Change-Id: I51a37d7dd7354d60668fc8a589da3e41470efba8

embdrv/lc3/Android.bp

diff --git a/embdrv/lc3/Android.bp b/embdrv/lc3/Android.bp
index 834e4bb..a02d039 100644
--- a/embdrv/lc3/Android.bp
+++ b/embdrv/lc3/Android.bp
@@ -18,6 +18,7 @@
     defaults: ["fluoride_defaults"],
     srcs: [
         "Common/*.cpp",
+        "Common/fft/*.c",
         "Common/Tables/*.cpp",
         "Encoder/*.cpp",
         "Decoder/*.cpp",
@@ -46,6 +47,7 @@
     export_include_dirs: [
         "Api",
         "Common",
+        "Common/fft",
         "Common/Tables",
         "TestSupport",
     ],

embdrv/lc3/Common/DctIV.cpp

diff --git a/embdrv/lc3/Common/DctIV.cpp b/embdrv/lc3/Common/DctIV.cpp
index 8500ab2..0fd4684 100644
--- a/embdrv/lc3/Common/DctIV.cpp
+++ b/embdrv/lc3/Common/DctIV.cpp
@@ -64,8 +64,7 @@
  * really wanted to make sure, that no other code or build impact is generated
  * by the options in this file.
  */
-//TODO: pick a FFT implementation library
-//#define USE_KISSFFT
+#define USE_OWN_FFT
 
 #if defined USE_FFTW || defined USE_FFTW_FOR_FFT
 #include <fftw3.h>
@@ -116,6 +115,8 @@
   kissfft<double>* fft;
 };
 
+#elif defined USE_OWN_FFT
+#include "fft.h"
 #endif
 
 DctIVDbl::DctIVDbl(uint16_t NF_)
@@ -134,6 +135,8 @@
 #elif defined USE_KISSFFT
   dctIVconfig = new KissfftConfig(NF / 2);
 
+#elif defined USE_OWN_FFT
+// setup is not needed
 #endif
 
   for (uint16_t n = 0; n < NF; n++) {
@@ -155,6 +158,8 @@
     delete kissfftConfig;
   }
 
+#elif defined USE_OWN_FFT
+// cleanup is not needed
 #endif
   if (nullptr != in) {
     delete[] in;
@@ -232,6 +237,31 @@
     out[NF - 2 * n - 1] = -complexOut.imag() * 2;
   }
 
+#elif defined USE_OWN_FFT
+
+  fft_complex inbuf[NF / 2];
+  fft_complex outbuf[NF / 2];
+
+  // assume NF being 4 times an integer
+  for (uint16_t n = 1; n < NF / 2; n += 2) {
+    double buffer;
+    buffer = in[n];
+    in[n] = in[NF - n];
+    in[NF - n] = buffer;
+  }
+
+  for (uint16_t n = 0; n < NF / 2; n++) {
+    inbuf[n].re = in[2 * n];
+    inbuf[n].im = in[2 * n + 1];
+  }
+
+  fft_complex* actal_output = fft(false, inbuf, NF / 2, inbuf, outbuf);
+
+  for (uint16_t n = 0; n < NF / 2; n++) {
+    out[2 * n] = actal_output[n].re;
+    out[NF - 2 * n - 1] = actal_output[n].im;
+  }
+
 #else
   DctIVDirectDbl(NF, in, out);
 #endif