Sample-Rate Conversion by the Giant FFT Revisited—A Theoretical and Experimental Investigation

High-quality sample-rate conversion (SRC) is essential in audio applications and remains a central concern in audio engineering. This paper focuses on the Giant FFT conversion method introduced by Välimäki and Bilbao in 2023, using the ideal sinc-based SRC as reference. In this context, the evaluation and control of the time-domain aliasing error play an important role. The contribution of this paper is threefold. First, a formal analysis relates the Giant FFT conversion method to the sinc-based reference, with corresponding mathematical derivations. Second, a time-domain zero-padding strategy is proposed to mitigate inherent time-domain aliasing, together with formulas to estimate conversion-error bounds relative to the reference. Third, a correlation-based approach enables efficient computation of the time-domain aliasing error on standard PC hardware within seconds for typical audio tracks. This evaluation determines the zero-padding length required for a desired accuracy. Experimental results with audio and other test signals confirm the analysis. The extended method enables efficient offline SRC with the possibility of reducing time-domain aliasing errors to negligible levels in professional audio applications.