KissFFT前进/逆输出噪音，为什么呢？ [英] KissFFT forward / inverse is outputting noise, why?
本文介绍了KissFFT前进/逆输出噪音，为什么呢？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我想在一个Java应用程序本身使用KissFFT，但输入信号的正向/反向没有返回，因为它应该：信号幅度几乎是不存在的。如果删除了缩放因子（由2N分割），则结果为谐波噪声。任何人都可以发现的bug？
下面是转接呼叫（GDX从复制，所以应该OK了！）：
JNIEXPORT无效JNICALL Java_com_badlogic_gdx_audio_analysis_KissFFT_spectrum（JNIEnv的* ENV，JCLASS clazz所jlong手柄，jshortArray obj_samples，jfloatArray obj_spectrum）{
短*样品=（短*）env-＆GT; GetPrimitiveArrayCritical（obj_samples，0）;
浮动*谱=（浮点*）env-＆GT; GetPrimitiveArrayCritical（obj_spectrum，0）; KissFFT * FFT =（KissFFT *）处理;
kiss_fftr（fft-＆GT; forwardConfig，（kiss_fft_scalar *）样品，fft-＆GT;谱）; INT LEN = fft-＆GT; NUMSAMPLES / 2 + 1;
的for（int i = 0; I＆LT; LEN，我++）
{
浮重=规模（fft-＆GT;谱[I] .R）* fft-＆GT; NUMSAMPLES;
浮IM =规模（fft-＆GT;谱[I] .7）* fft-＆GT; NUMSAMPLES; 如果（I 0）
谱[I] = sqrtf（重*重新+ IM * IM）;
其他
谱[I] = sqrtf（重*重新+ IM * IM）;
} env-＆GT; ReleasePrimitiveArrayCritical（obj_samples，样品，0）;
env-＆GT; ReleasePrimitiveArrayCritical（obj_spectrum，频谱，0）;}
这是逆（我写的，可能有一个错误;））：
JNIEXPORT无效JNICALL Java_com_badlogic_gdx_audio_analysis_KissFFT_inverse（JNIEnv的* ENV，JCLASS clazz所jlong手柄，jshortArray obj_samples）{
短* shortSamples =（短*）env-＆GT; GetPrimitiveArrayCritical（obj_samples，0）;// @行：108 KissFFT * FFT =（KissFFT *）处理;
kiss_fft_cpx出[fft-＆GT; NUMSAMPLES]。 kiss_fftri（fft-＆GT; inverseConfig，fft-＆GT;谱，（kiss_fft_scalar *）出）; 的for（int i = 0; I＆LT; fft-＆GT; NUMSAMPLES;我++）{
shortSamples [I] =（出[I] .R）/（fft-＆GT; NUMSAMPLES * 2）;
} env-＆GT; ReleasePrimitiveArrayCritical（obj_samples，shortSamples，0）;}
解决方案
每protectedmember的要求，这里是一个更完整的例子（在本机端，反正）。我结束了小幅修改libgdx code（使用v.0.9.4）。当反演我也编译了浮点，而不是固定的，因为后者引入的量化噪声。这code的应的对或者（因为kiss_fft_scalar适应短期或浮动取决于编译器的标志），但没有固定重新测试，因为我发现它不是一个fft-有益的工作> IFFT系列。
我很想知道，如果你成功了，你让我知道！
（请注意，这code，以下libgdx，是根据Apache 2.0许可！）
的#include＆LT; com.badlogic.gdx.audio.analysis.KissFFT.h＆GT;＃包括LT＆; kissfft / kiss_fftr.h＆GT;
＃包括LT＆;＆stdlib.h中GT;
＃包括LT＆;＆stdio.h中GT;
＃包括LT＆;＆math.h中GT;结构KissFFT
{
kiss_fftr_cfg forwardConfig;
kiss_fftr_cfg inverseConfig;
kiss_fft_cpx *谱;
INT NUMSAMPLES;
INT spectrumSize;
};JNIEXPORT jlong JNICALL Java_com_badlogic_gdx_audio_analysis_KissFFT_create（JNIEnv的* ENV，JCLASS clazz所jint NUMSAMPLES）{ KissFFT * FFT =新KissFFT（）;
fft-＆GT; forwardConfig = kiss_fftr_alloc（NUMSAMPLES，0，NULL，NULL）;
fft-＆GT; inverseConfig = kiss_fftr_alloc（NUMSAMPLES，1，NULL，NULL）;
fft-＆GT;谱=（kiss_fft_cpx *）malloc的（的sizeof（kiss_fft_cpx）* NUMSAMPLES）;
fft-＆GT; NUMSAMPLES = NUMSAMPLES;
fft-＆GT; spectrumSize = NUMSAMPLES / 2 + 1;
回报（jlong）FFT;
}JNIEXPORT无效JNICALL Java_com_badlogic_gdx_audio_analysis_KissFFT_destroy（JNIEnv的* ENV，JCLASS clazz所jlong手柄）{ KissFFT * FFT =（KissFFT *）处理;
免费（fft-＆GT; forwardConfig）;
免费（fft-＆GT; inverseConfig）;
免费（fft-＆GT;谱）;
免费（FFT）;
}JNIEXPORT无效JNICALL Java_com_badlogic_gdx_audio_analysis_KissFFT_spectrum（JNIEnv的* ENV，JCLASS clazz所jlong手柄，jfloatArray obj_samples，jfloatArray obj_mags）{ kiss_fft_scalar *样品=（kiss_fft_scalar *）env-＆GT; GetPrimitiveArrayCritical（obj_samples，0）;
浮动*弹匣=（浮点*）env-＆GT; GetPrimitiveArrayCritical（obj_mags，0）; KissFFT * FFT =（KissFFT *）处理; kiss_fftr（fft-＆GT; forwardConfig，样品，fft-＆GT;谱）; 的for（int i = 0; I＆LT; fft-＆GT; spectrumSize;我++）{
弹匣[I] = hypotf（fft-＆GT;谱[I] .R，fft-＆GT;谱[I] .7）;
} env-＆GT; ReleasePrimitiveArrayCritical（obj_samples，样品，0）;
env-＆GT; ReleasePrimitiveArrayCritical（obj_mags，弹匣，0）;
}JNIEXPORT无效JNICALL Java_com_badlogic_gdx_audio_analysis_KissFFT_inverse（JNIEnv的* ENV，JCLASS clazz所jlong手柄，jfloatArray obj_samples）{
kiss_fft_scalar *样品=（kiss_fft_scalar *）env-＆GT; GetPrimitiveArrayCritical（obj_samples，0）; KissFFT * FFT =（KissFFT *）处理; kiss_fftri（fft-＆GT; inverseConfig，fft-＆GT;光谱样本）; 的for（int i = 0; I＆LT; fft-＆GT; NUMSAMPLES;我++）{
样本[I] =样本[I] /（浮点）fft-＆GT; NUMSAMPLES;
} env-＆GT; ReleasePrimitiveArrayCritical（obj_samples，样品，0）;}
I'm trying to use KissFFT natively in a java app, but the forward/inverse of an input signal isn't returning as it should: the signal amplitude is almost non-existent. If I remove the scaling factor (dividing by 2N), the result is harmonic noise. Can anyone spot the bug?
Here is the forward call (copied from GDX, so should be ok!):
JNIEXPORT void JNICALL Java_com_badlogic_gdx_audio_analysis_KissFFT_spectrum(JNIEnv* env, jclass clazz, jlong handle, jshortArray obj_samples, jfloatArray obj_spectrum) {
short* samples = (short*)env->GetPrimitiveArrayCritical(obj_samples, 0);
float* spectrum = (float*)env->GetPrimitiveArrayCritical(obj_spectrum, 0);
KissFFT* fft = (KissFFT*)handle;
kiss_fftr( fft->forwardConfig, (kiss_fft_scalar*)samples, fft->spectrum );
int len = fft->numSamples / 2 + 1;
for( int i = 0; i < len; i++ )
{
float re = scale(fft->spectrum[i].r) * fft->numSamples;
float im = scale(fft->spectrum[i].i) * fft->numSamples;
if( i > 0 )
spectrum[i] = sqrtf(re*re + im*im);
else
spectrum[i] = sqrtf(re*re + im*im);
}
env->ReleasePrimitiveArrayCritical(obj_samples, samples, 0);
env->ReleasePrimitiveArrayCritical(obj_spectrum, spectrum, 0);
}
And here is the inverse (written by me, probably has an error ;) ):
JNIEXPORT void JNICALL Java_com_badlogic_gdx_audio_analysis_KissFFT_inverse(JNIEnv* env, jclass clazz, jlong handle, jshortArray obj_samples) {
short* shortSamples = (short*)env->GetPrimitiveArrayCritical(obj_samples, 0);
//@line:108
KissFFT* fft = (KissFFT*)handle;
kiss_fft_cpx out[fft->numSamples];
kiss_fftri( fft->inverseConfig, fft->spectrum, (kiss_fft_scalar*)out );
for (int i=0; i < fft->numSamples; i++) {
shortSamples[i] = (out[i].r) / (fft->numSamples*2);
}
env->ReleasePrimitiveArrayCritical(obj_samples, shortSamples, 0);
}
解决方案
Per protectedmember's request, here is a more complete example (on the native side, anyway). I ended up modifying the libgdx code slightly (using v.0.9.4). I also compiled with floating-point rather than fixed, as the latter introduced quantization noise when inversing. This code should work for either (because kiss_fft_scalar adapts to short or float depending on the compiler flag), but have not re-tested with fixed, since I found it's not useful for a fft->ifft series.
I am curious to know if you are successful, do let me know!
(Please note that this code, following libgdx, is under Apache 2.0 license!)
#include <com.badlogic.gdx.audio.analysis.KissFFT.h>
#include <kissfft/kiss_fftr.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
struct KissFFT
{
kiss_fftr_cfg forwardConfig;
kiss_fftr_cfg inverseConfig;
kiss_fft_cpx* spectrum;
int numSamples;
int spectrumSize;
};
JNIEXPORT jlong JNICALL Java_com_badlogic_gdx_audio_analysis_KissFFT_create(JNIEnv* env, jclass clazz, jint numSamples) {
KissFFT* fft = new KissFFT();
fft->forwardConfig = kiss_fftr_alloc(numSamples,0,NULL,NULL);
fft->inverseConfig = kiss_fftr_alloc(numSamples,1,NULL,NULL);
fft->spectrum = (kiss_fft_cpx*)malloc(sizeof(kiss_fft_cpx) * numSamples);
fft->numSamples = numSamples;
fft->spectrumSize = numSamples/2+1;
return (jlong)fft;
}
JNIEXPORT void JNICALL Java_com_badlogic_gdx_audio_analysis_KissFFT_destroy(JNIEnv* env, jclass clazz, jlong handle) {
KissFFT* fft = (KissFFT*)handle;
free(fft->forwardConfig);
free(fft->inverseConfig);
free(fft->spectrum);
free(fft);
}
JNIEXPORT void JNICALL Java_com_badlogic_gdx_audio_analysis_KissFFT_spectrum(JNIEnv* env, jclass clazz, jlong handle, jfloatArray obj_samples, jfloatArray obj_mags) {
kiss_fft_scalar* samples = (kiss_fft_scalar*)env->GetPrimitiveArrayCritical(obj_samples, 0);
float* mags = (float*)env->GetPrimitiveArrayCritical(obj_mags, 0);
KissFFT* fft = (KissFFT*) handle;
kiss_fftr(fft->forwardConfig, samples, fft->spectrum);
for(int i=0;i<fft->spectrumSize;i++) {
mags[i] = hypotf(fft->spectrum[i].r,fft->spectrum[i].i);
}
env->ReleasePrimitiveArrayCritical(obj_samples, samples, 0);
env->ReleasePrimitiveArrayCritical(obj_mags, mags, 0);
}
JNIEXPORT void JNICALL Java_com_badlogic_gdx_audio_analysis_KissFFT_inverse(JNIEnv* env, jclass clazz, jlong handle, jfloatArray obj_samples) {
kiss_fft_scalar* samples = (kiss_fft_scalar*)env->GetPrimitiveArrayCritical(obj_samples, 0);
KissFFT* fft = (KissFFT*)handle;
kiss_fftri( fft->inverseConfig, fft->spectrum, samples );
for(int i=0;i<fft->numSamples;i++) {
samples[i] = samples[i] / (float)fft->numSamples;
}
env->ReleasePrimitiveArrayCritical(obj_samples, samples, 0);
}
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