Writing a DSP effect plugin

DSP plugins (AMP_PLUGIN_DSP, type 1) implement amp_plugin_dsp_process(float* samples, int frames, int channels) and process interleaved float PCM in place. It runs on the audio thread, so it MUST be realtime-safe: no allocation, no locks, no I/O. Declare parameters with amp_plugin_get_param_info() and the host renders a UI automatically. Start from templates/dsp-plugin-template.c; the MC1 Crossfader example shows std::atomic for thread-safe params.