GMF FFT

[δΈ­ζ–‡]

GMF FFT is a fixed-point Q15 real FFT/IFFT component for ESP-IDF. It uses the int16_t Q15 data format to reduce computational and storage overhead. The implementation includes a generic C version and PIE vector assembly optimizations for Xtensa / RISC-V, achieving lower latency than a pure-software DIT at typical sizes. By exploiting the Hermitian conjugate symmetry of real signals, the forward transform retains only N/2 + 1 frequency bins, halving the frequency-domain storage and computation overhead. Suitable for embedded scenarios without FPU or with tight latency requirements.

Key Features

  • Real FFT / IFFT: power-of-2 lengths from 32 to 8192 points

  • Q15 fixed-point data: int16_t format, reducing computational and storage cost

  • Real-signal optimization: Hermitian conjugate symmetry; the forward transform outputs only N/2 + 1 frequency bins

  • Hardware acceleration: PIE vector assembly optimizations for Xtensa / RISC-V; latency at typical lengths is lower than pure-software implementations

  • Generic fallback: a C version is included in the package and runs on SoCs without PIE

  • Thread-safe: the same handle can be shared by multiple threads as long as each thread uses its own buffer

  • Use cases: real-time signal processing without FPU or with tight latency requirements

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