FFT benchmark

Opus decoding and ESP-DSP transform benchmarks during SFU streaming. The frozen Rust radio harness in firmware/ supplies the streaming workload; a C task on core 1 runs the benchmarks.

The benchmark checks known sine-wave bins, then measures 1,024- and 2,048-point floating-point and fixed-point transforms over 2,500 audio packets per phase. It reports decoder time, transform time, queue latency, dropped packets, internal memory, and stack headroom. Bands from this benchmark go to the USB console; the harness transmits precomputed spectrum.

The maintained firmware documents the Rust analysis task, its ESP-DSP floating-point kernel, and lifetime contracts.

Follow the archive setup, including SIGNALING_URL. The frozen music reader requires a version 1 pack; archive preparation writes it separately from the maintained radio's music:

.tools/archive-python/bin/python archive/prepare-music.py /path/to/audio.flac
python3 archive/fft-benchmark/build.py
.tools/archive-python/bin/python archive/flash.py fft-benchmark

Observe the native USB console with a serial monitor. FFT_SELF_TEST, FFT_READY, FFT_RESULT, and FFT_COMPLETE identify the bounded measurement. The two phases take approximately 100 seconds after packets start arriving. Open the exhibit to add listeners when reproducing the streaming workload. After FFT_COMPLETE, the benchmark retains allocations until reboot.

Record the audio input, listener count, and dependency pins when comparing measurements. Keep serial logs under artifacts/archive/fft-benchmark/ and restore the maintained firmware and music using the archive guide.