Unsupervised Wrap-Discontinuity Repair in Wavetable Synthesis via Hybrid GA–PPO Meta-Search

Abstract

In single-period wavetable synthesis, a sample discontinuity at the wrap boundary injects a broadband transient that repeats at the fundamental frequency, producing an audible periodic click. We address this cycle-local seam artifact with DenoiseOpt, a residualscored hybrid meta-search that selects and fits bake-cell operators applied at the period boundary. The bake cell composes classical DualCosine crossfades, FIR blends, and optional lightweight residual networks, possibly routed via Mixture-of-Experts (MoE) soft gating, without requiring paired studio-clean recordings. Candidates are ranked by the prolonged residual score R ∈ [0,1] (higher is better): the clamped tiled-RMS agreement between the baked multi-period output and a procedural ideal sibling that suppresses the open-wrap cliff. The outer search loop interleaves genetic algorithm (GA) tournament selection, PPO-based architecture proposals, and optional population-based training (PBT). On a frozen canonical sine+cliff holdout (seed 20260719), the compact metafavorite achieves R ≈ 0.991 versus DualCosine R ≈ 0.825 (∆R = +0.166). In an overnight GPU campaign (RTX 3090, 5,000 clean iterations), the champion reaches R ≈ 0.9909 versus DualCosine ≈ 0.8166 (∆R ≈ +0.174). Across twenty multi-family generative draws, mean ∆R = +0.162 over DualCosine (Wilcoxon p ≈ 8.9×10−5).

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