Constant ROUNDING_SCAN_BYTES 

pub const ROUNDING_SCAN_BYTES: u64 = _ /* 16_777_216u64 */;

The packet bytes past which a host reads no more of a stream’s first packets for rounding_quantum (16 MiB): a native decoder keeps the packets it read until it decodes them, so a 4K stream is held to about a second of them.