Function rfft_batch

src/common/audio_process_utils/audioproc.cpp:11–48

namespace audioproc {

    void rfft_batch(
        const float* frames,
        float* out_complex,
        int num_frames,
        int frame_length,
        int fft_length)
    {
        const int n_bins = fft_length / 2 + 1;

        // Allocate FFTW buffers
        float* fft_in = (float*)fftwf_malloc(fft_length * sizeof(float));
        fftwf_complex* fft_out = (fftwf_complex*)fftwf_malloc(n_bins * sizeof(fftwf_complex));

        // Create plan (FFTW_ESTIMATE for fast planning)
        fftwf_plan plan = fftwf_plan_dft_r2c_1d(fft_length, fft_in, fft_out, FFTW_ESTIMATE);

        for (int f = 0; f < num_frames; ++f) {
            // Copy frame data
            std::memcpy(fft_in, frames + f * frame_length, frame_length * sizeof(float));
            // Zero-pad if fft_length > frame_length
            if (fft_length > frame_length) {
                std::memset(fft_in + frame_length, 0, (fft_length - frame_length) * sizeof(float));
            }

            fftwf_execute(plan);

            // Copy interleaved (re, im) output
            float* dst = out_complex + f * n_bins * 2;
            for (int k = 0; k < n_bins; ++k) {
                dst[2 * k]     = fft_out[k][0]; // real
                dst[2 * k + 1] = fft_out[k][1]; // imag
            }
        }

        fftwf_destroy_plan(plan);
        fftwf_free(fft_in);
        fftwf_free(fft_out);
    }

    void rfft_magnitude_batch(
        const float* frames,