add fixed fft

app/CMakeLists.txt

@@ -35,6 +35,7 @@ add_library( # Sets the name of the library.
             src/main/cpp/fast_start.c
             src/main/cpp/ffprobe_cmd.cpp
             src/main/cpp/visualizer/fft.cpp
+            src/main/cpp/visualizer/fixed_fft.cpp
             src/main/cpp/visualizer/block_queue.c
             src/main/cpp/visualizer/execute_fft.cpp
             src/main/cpp/visualizer/window.cpp

app/src/main/cpp/visualizer/execute_fft.cpp

@@ -110,7 +110,7 @@ static void *fft_thread(void *p_data)
         /* Convert the buffer to int16_t */
         for (i = block->i_nb_samples * p_sys->i_channels; i--;)
         {
-            union {float f; int32_t i;} u;
+            union {float f; int32_t i;} u{};
 
             u.f = *p_buffl + 384.f;
             if (u.i > 0x43c07fff)
@@ -276,7 +276,7 @@ void fft_once(filter_sys_t *p_sys)
     /* Convert the buffer to int16_t */
     for (i = nb_samples * p_sys->i_channels; i--;)
     {
-        union {float f; int32_t i;} u;
+        union {float f; int32_t i;} u{};
 
         u.f = *p_buffl + 384.f;
         if (u.i > 0x43c07fff)
@@ -323,3 +323,56 @@ release:
     window_close(&wind_ctx);
     fft_close(p_state);
 }
+
+int doFft(uint8_t *fft, const uint8_t *waveform, int mCaptureSize)
+{
+    int32_t workspace[mCaptureSize >> 1];
+    int32_t nonzero = 0;
+
+    for (uint32_t i = 0; i < mCaptureSize; i += 2) {
+        workspace[i >> 1] =
+                ((waveform[i] ^ 0x80) << 24) | ((waveform[i + 1] ^ 0x80) << 8);
+        nonzero |= workspace[i >> 1];
+    }
+
+    if (nonzero) {
+        fixed_fft_real(mCaptureSize >> 1, workspace);
+    }
+
+    for (uint32_t i = 0; i < mCaptureSize; i += 2) {
+        short tmp = workspace[i >> 1] >> 21;
+        while (tmp > 127 || tmp < -128) tmp >>= 1;
+        fft[i] = tmp;
+        tmp = workspace[i >> 1];
+        tmp >>= 5;
+        while (tmp > 127 || tmp < -128) tmp >>= 1;
+        fft[i + 1] = tmp;
+    }
+
+    return 0;
+}
+
+void fft_fixed(filter_sys_t *p_sys)
+{
+    int nb_samples = p_sys->nb_samples;
+    int out_samples = p_sys->out_samples;
+
+    DEFINE_WIND_CONTEXT(wind_ctx); /* internal window data */
+
+    if (!nb_samples) {
+        LOGE("no samples yet...");
+        goto release;
+    }
+
+    if (!window_init(out_samples, &p_sys->wind_param, &wind_ctx))
+    {
+        LOGE("unable to initialize FFT window...");
+        goto release;
+    }
+
+    window_scale_in_place ((int16_t *) (p_sys->data), &wind_ctx);
+    doFft((uint8_t *) p_sys->output, p_sys->data, out_samples);
+
+    release:
+    window_close(&wind_ctx);
+}

app/src/main/cpp/visualizer/execute_fft.h

@@ -9,6 +9,7 @@
 #include <unistd.h>
 #include "fft.h"
 #include "window.h"
+#include "fixed_fft.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -51,6 +52,8 @@ void release_visualizer(filter_sys_t *p_sys);
 
 int ensure_memory(filter_sys_t *fft_filter, int nb_samples);
 
+void fft_fixed(filter_sys_t *p_sys);
+
 #ifdef __cplusplus
 }
 #endif

app/src/main/cpp/visualizer/fixed_fft.cpp

@@ -0,0 +1,148 @@
+
+/* A Fixed point implementation of Fast Fourier Transform (FFT). Complex numbers
+ * are represented by 32-bit integers, where higher 16 bits are real part and
+ * lower ones are imaginary part. Few compromises are made between efficiency,
+ * accuracy, and maintainability. To make it fast, arithmetic shifts are used
+ * instead of divisions, and bitwise inverses are used instead of negates. To
+ * keep it small, only radix-2 Cooley-Tukey algorithm is implemented, and only
+ * half of the twiddle factors are stored. Although there are still ways to make
+ * it even faster or smaller, it costs too much on one of the aspects.
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+
+#include "fixed_fft.h"
+
+#define LOG_FFT_SIZE 10
+#define MAX_FFT_SIZE (1 << LOG_FFT_SIZE)
+
+// Actually int32_t, but declare as uint32_t to avoid warnings due to overflow.
+// Be sure to cast all accesses before use, for example "(int32_t) twiddle[...]".
+static const uint32_t twiddle[MAX_FFT_SIZE / 4] = {
+    0x00008000, 0xff378001, 0xfe6e8002, 0xfda58006, 0xfcdc800a, 0xfc13800f,
+    0xfb4a8016, 0xfa81801e, 0xf9b88027, 0xf8ef8032, 0xf827803e, 0xf75e804b,
+    0xf6958059, 0xf5cd8068, 0xf5058079, 0xf43c808b, 0xf374809e, 0xf2ac80b2,
+    0xf1e480c8, 0xf11c80de, 0xf05580f6, 0xef8d8110, 0xeec6812a, 0xedff8146,
+    0xed388163, 0xec718181, 0xebab81a0, 0xeae481c1, 0xea1e81e2, 0xe9588205,
+    0xe892822a, 0xe7cd824f, 0xe7078276, 0xe642829d, 0xe57d82c6, 0xe4b982f1,
+    0xe3f4831c, 0xe3308349, 0xe26d8377, 0xe1a983a6, 0xe0e683d6, 0xe0238407,
+    0xdf61843a, 0xde9e846e, 0xdddc84a3, 0xdd1b84d9, 0xdc598511, 0xdb998549,
+    0xdad88583, 0xda1885be, 0xd95885fa, 0xd8988637, 0xd7d98676, 0xd71b86b6,
+    0xd65c86f6, 0xd59e8738, 0xd4e1877b, 0xd42487c0, 0xd3678805, 0xd2ab884c,
+    0xd1ef8894, 0xd13488dd, 0xd0798927, 0xcfbe8972, 0xcf0489be, 0xce4b8a0c,
+    0xcd928a5a, 0xccd98aaa, 0xcc218afb, 0xcb698b4d, 0xcab28ba0, 0xc9fc8bf5,
+    0xc9468c4a, 0xc8908ca1, 0xc7db8cf8, 0xc7278d51, 0xc6738dab, 0xc5c08e06,
+    0xc50d8e62, 0xc45b8ebf, 0xc3a98f1d, 0xc2f88f7d, 0xc2488fdd, 0xc198903e,
+    0xc0e990a1, 0xc03a9105, 0xbf8c9169, 0xbedf91cf, 0xbe329236, 0xbd86929e,
+    0xbcda9307, 0xbc2f9371, 0xbb8593dc, 0xbadc9448, 0xba3394b5, 0xb98b9523,
+    0xb8e39592, 0xb83c9603, 0xb7969674, 0xb6f196e6, 0xb64c9759, 0xb5a897ce,
+    0xb5059843, 0xb46298b9, 0xb3c09930, 0xb31f99a9, 0xb27f9a22, 0xb1df9a9c,
+    0xb1409b17, 0xb0a29b94, 0xb0059c11, 0xaf689c8f, 0xaecc9d0e, 0xae319d8e,
+    0xad979e0f, 0xacfd9e91, 0xac659f14, 0xabcd9f98, 0xab36a01c, 0xaaa0a0a2,
+    0xaa0aa129, 0xa976a1b0, 0xa8e2a238, 0xa84fa2c2, 0xa7bda34c, 0xa72ca3d7,
+    0xa69ca463, 0xa60ca4f0, 0xa57ea57e, 0xa4f0a60c, 0xa463a69c, 0xa3d7a72c,
+    0xa34ca7bd, 0xa2c2a84f, 0xa238a8e2, 0xa1b0a976, 0xa129aa0a, 0xa0a2aaa0,
+    0xa01cab36, 0x9f98abcd, 0x9f14ac65, 0x9e91acfd, 0x9e0fad97, 0x9d8eae31,
+    0x9d0eaecc, 0x9c8faf68, 0x9c11b005, 0x9b94b0a2, 0x9b17b140, 0x9a9cb1df,
+    0x9a22b27f, 0x99a9b31f, 0x9930b3c0, 0x98b9b462, 0x9843b505, 0x97ceb5a8,
+    0x9759b64c, 0x96e6b6f1, 0x9674b796, 0x9603b83c, 0x9592b8e3, 0x9523b98b,
+    0x94b5ba33, 0x9448badc, 0x93dcbb85, 0x9371bc2f, 0x9307bcda, 0x929ebd86,
+    0x9236be32, 0x91cfbedf, 0x9169bf8c, 0x9105c03a, 0x90a1c0e9, 0x903ec198,
+    0x8fddc248, 0x8f7dc2f8, 0x8f1dc3a9, 0x8ebfc45b, 0x8e62c50d, 0x8e06c5c0,
+    0x8dabc673, 0x8d51c727, 0x8cf8c7db, 0x8ca1c890, 0x8c4ac946, 0x8bf5c9fc,
+    0x8ba0cab2, 0x8b4dcb69, 0x8afbcc21, 0x8aaaccd9, 0x8a5acd92, 0x8a0cce4b,
+    0x89becf04, 0x8972cfbe, 0x8927d079, 0x88ddd134, 0x8894d1ef, 0x884cd2ab,
+    0x8805d367, 0x87c0d424, 0x877bd4e1, 0x8738d59e, 0x86f6d65c, 0x86b6d71b,
+    0x8676d7d9, 0x8637d898, 0x85fad958, 0x85beda18, 0x8583dad8, 0x8549db99,
+    0x8511dc59, 0x84d9dd1b, 0x84a3dddc, 0x846ede9e, 0x843adf61, 0x8407e023,
+    0x83d6e0e6, 0x83a6e1a9, 0x8377e26d, 0x8349e330, 0x831ce3f4, 0x82f1e4b9,
+    0x82c6e57d, 0x829de642, 0x8276e707, 0x824fe7cd, 0x822ae892, 0x8205e958,
+    0x81e2ea1e, 0x81c1eae4, 0x81a0ebab, 0x8181ec71, 0x8163ed38, 0x8146edff,
+    0x812aeec6, 0x8110ef8d, 0x80f6f055, 0x80def11c, 0x80c8f1e4, 0x80b2f2ac,
+    0x809ef374, 0x808bf43c, 0x8079f505, 0x8068f5cd, 0x8059f695, 0x804bf75e,
+    0x803ef827, 0x8032f8ef, 0x8027f9b8, 0x801efa81, 0x8016fb4a, 0x800ffc13,
+    0x800afcdc, 0x8006fda5, 0x8002fe6e, 0x8001ff37,
+};
+
+/* Returns the multiplication of \conj{a} and {b}. */
+static inline int32_t mult(int32_t a, int32_t b)
+{
+#if defined(__arm__)
+    int32_t t = b;
+    __asm__("smuad  %0, %0, %1"          : "+r" (t) : "r" (a));
+    __asm__("smusdx %0, %0, %1"          : "+r" (b) : "r" (a));
+    __asm__("pkhtb  %0, %0, %1, ASR #16" : "+r" (t) : "r" (b));
+    return t;
+#else
+    return (((a >> 16) * (b >> 16) + (int16_t)a * (int16_t)b) & ~0xFFFF) |
+        ((((a >> 16) * (int16_t)b - (int16_t)a * (b >> 16)) >> 16) & 0xFFFF);
+#endif
+}
+
+static inline int32_t half(int32_t a)
+{
+#if defined(__arm__)
+    __asm__("shadd16 %0, %0, %1" : "+r" (a) : "r" (0));
+    return a;
+#else
+    return ((a >> 1) & ~0x8000) | (a & 0x8000);
+#endif
+}
+
+void fixed_fft(int n, int32_t *v)
+{
+    int scale = LOG_FFT_SIZE, i, p, r;
+
+    for (r = 0, i = 1; i < n; ++i) {
+        for (p = n; !(p & r); p >>= 1, r ^= p);
+        if (i < r) {
+            int32_t t = v[i];
+            v[i] = v[r];
+            v[r] = t;
+        }
+    }
+
+    for (p = 1; p < n; p <<= 1) {
+        --scale;
+
+        for (i = 0; i < n; i += p << 1) {
+            int32_t x = half(v[i]);
+            int32_t y = half(v[i + p]);
+            v[i] = x + y;
+            v[i + p] = x - y;
+        }
+
+        for (r = 1; r < p; ++r) {
+            int32_t w = MAX_FFT_SIZE / 4 - (r << scale);
+            i = w >> 31;
+            w = ((int32_t) twiddle[(w ^ i) - i]) ^ (i << 16);
+            for (i = r; i < n; i += p << 1) {
+                int32_t x = half(v[i]);
+                int32_t y = mult(w, v[i + p]);
+                v[i] = x - y;
+                v[i + p] = x + y;
+            }
+        }
+    }
+}
+
+void fixed_fft_real(int n, int32_t *v)
+{
+    int scale = LOG_FFT_SIZE, m = n >> 1, i;
+
+    fixed_fft(n, v);
+    for (i = 1; i <= n; i <<= 1, --scale);
+    v[0] = mult(~v[0], 0x80008000);
+    v[m] = half(v[m]);
+
+    for (i = 1; i < n >> 1; ++i) {
+        int32_t x = half(v[i]);
+        int32_t z = half(v[n - i]);
+        int32_t y = z - (x ^ 0xFFFF);
+        x = half(x + (z ^ 0xFFFF));
+        y = mult(y, ((int32_t) twiddle[i << scale]));
+        v[i] = x - y;
+        v[n - i] = (x + y) ^ 0xFFFF;
+    }
+}

app/src/main/cpp/visualizer/fixed_fft.h

@@ -0,0 +1,11 @@
+
+#ifndef FIXED_FFT_H
+#define FIXED_FFT_H
+
+#include <stdint.h>
+
+
+extern void fixed_fft_real(int n, int32_t *v);
+
+
+#endif  // FIXED_FFT_H