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Answers checklist.
- I have read the ESP-DSP documentation and the issue is not addressed there.
- I have read the documentation ESP-IDF Programming Guide and the issue is not addressed there.
- I have updated my ESP-DSP branch (master or release) to the latest version and checked that the issue is present there.
- I have searched the issue tracker for a similar issue and not found a similar issue.
General issue report
我使用kissfft库的代码：
Matrix compute_spectrum(const Matrix &strided_input) {
AUTO_TIME(FFT,"fft")
int num_frames = strided_input.size();
int nfft = strided_input[0].size(); // FFT 长度
int fft_out_size = nfft / 2 + 1; // rFFT 输出大小
// 结果存储
Matrix magnitude_spectrum(num_frames, vector<float>(fft_out_size, 0.0f));
// 初始化 KissFFT 配置
kiss_fftr_cfg cfg = kiss_fftr_alloc(nfft, 0, nullptr, nullptr);
if (!cfg) {
return {magnitude_spectrum};
}
// 计算每一行的 FFT
for (int i = 0; i < num_frames; ++i) {
vector<kiss_fft_cpx> fft_output(fft_out_size);
kiss_fftr(cfg, strided_input[i].data(), fft_output.data());
// 计算幅度谱或功率谱
for (int j = 0; j < fft_out_size; ++j) {
float real = fft_output[j].r;
float imag = fft_output[j].i;
float magnitude = sqrt(real * real + imag * imag);
magnitude_spectrum[i][j] = use_power ? magnitude * magnitude : magnitude;
}
}
// 释放 FFT 资源
kiss_fft_free(cfg);
return magnitude_spectrum;
}
我使用kissfft库的结果：
输入是 298 个 512 维的矩阵，512维时域转到（512 /2+1）=257维频率
使用esp-dsp测试的代码:
#define N_SAMPLES 512
int N = N_SAMPLES;
// Input test array
__attribute__((aligned(16)))
float x1[N_SAMPLES];
__attribute__((aligned(16)))
float x2[N_SAMPLES];
// Window coefficients
__attribute__((aligned(16)))
float wind[N_SAMPLES];
// working complex array
__attribute__((aligned(16)))
float y_cf[N_SAMPLES * 2];
// Pointers to result arrays
float *y1_cf = &y_cf[0];
float *y2_cf = &y_cf[N_SAMPLES];
// Sum of y1 and y2
__attribute__((aligned(16)))
float sum_y[N_SAMPLES / 2];
extern const uint8_t input_start [] asm("_binary_input_bin_start");
extern const uint8_t input_end [] asm("_binary_input_bin_end");
extern "C" void app_main()
{
AUTO_TIME(ALL, "all");
float *input = (float *)input_start;
int input_size = (int)(input_end - input_start) / sizeof(float);
ESP_LOGI(TAG, "input_size = %d", input_size);
int rows = 298;
int cols = N;
esp_err_t ret;
ESP_LOGI(TAG, "Start Example.");
ret = dsps_fft2r_init_fc32(NULL, CONFIG_DSP_MAX_FFT_SIZE);
if (ret != ESP_OK) {
ESP_LOGE(TAG, "Not possible to initialize FFT. Error = %i", ret);
return;
}
unsigned int start_b;
unsigned int end_b;
{
AUTO_TIME(fft, "FFT");
for (int i = 0 ; i < N ; i++) {
x1[i] = input[i];
if(i<5){
std::cout << x1[i] << " ";
}
}
std::cout << std::endl;
for (int i = 0 ; i < N ; i++) {
x2[i] = input[i + N];
if(i<5){
std::cout << x2[i] << " ";
}
}
std::cout << std::endl;
// Convert two input vectors to one complex vector
for (int i = 0 ; i < N ; i++) {
y_cf[i * 2 + 0] = x1[i];
y_cf[i * 2 + 1] = 0;
}
// FFT
start_b = dsp_get_cpu_cycle_count();
dsps_fft2r_fc32(y_cf, N);
end_b = dsp_get_cpu_cycle_count();
// Bit reverse
dsps_bit_rev_fc32(y_cf, N);
// Convert one complex vector to two complex vectors
dsps_cplx2reC_fc32(y_cf, N);
}
std::vector<float> y1_cf_vec( N / 2);
std::vector<float> y2_cf_vec( N / 2);
for (int i = 0 ; i < N / 2 ; i++) {
y1_cf_vec[i] = sqrt((y1_cf[i * 2 + 0] * y1_cf[i * 2 + 0] + y1_cf[i * 2 + 1] * y1_cf[i * 2 + 1]));
y2_cf_vec[i] = sqrt((y2_cf[i * 2 + 0] * y2_cf[i * 2 + 0] + y2_cf[i * 2 + 1] * y2_cf[i * 2 + 1]));
}
for (int i = 0 ; i < 5 ; i++) {
std::cout << y1_cf_vec[i] * y1_cf_vec[i] << " ";
}
std::cout << std::endl;
for (int i = 0 ; i < 5 ; i++) {
std::cout << y2_cf_vec[i] * y2_cf_vec[i]<< " ";
}
std::cout << std::endl;
ESP_LOGI(TAG, "FFT for %i complex points take %i cycles", N, end_b - start_b);
ESP_LOGI(TAG, "End Example.");
}
使用esp-dsp测试的结果:
红色 1 是输入数据的一部分
红色 2 是输出数据的一部分
我们可以看到只有 黄色标记的第一个直流通量才是和kissfft的结果一致，其它的都不对，这是为什么呢？还有就是我们默认是257维的结果，为啥本项目中的fft这个demo的结果是256维，我要怎么做才能生成257维的结果