alt Hacker NewsI was also wondering about the inherent resolution for the BPM precision claims.
Besides the sample period, the total number of samples matter for frequency resolution (aka BPM precision).
44100 Hz sampling frequency (22.675737 us period) for 216.276 s is 9537772 samples (rounding to nearest integer). This gives frequency samples with a bandsize of 0.0046237213 Hz which is 0.27742328 BPM.
Any claim of a BPM more precise than about 0.3 BPM is "creative interpretation".
And this is a minimum precision. Peaks in real-world spectra have width which further reduces the precision of their location.
Edit to add:
This takes my flac rip of the CD and simply uses the full song waveform. This artificially increases frequency precision by a little compared to taking only the time span where beats are occurring.
This is plainly false though. You're saying beats can't be localized to less than one second of precision (regardless of track length, which already smells suspect). Humans can localize a beat to within 50ms.