Function page_start 

fn page_start(position: u64, granule: u64, samples: u64) -> u64

Where a page’s first packet starts, in samples: its granule position counts to the end of its last packet, so the page starts what its packets hold (samples) before that. A producer that sends nothing through a silence (pcmflux’s silence gate) leaves the gap before the page, which then lands after it rather than against the page before; a final page whose granule trims its end starts where the one before ended.