Function spsc 

pub fn spsc(
    capacity_samples: usize,
    channels: u16,
) -> (SampleProducer, SampleConsumer)

Create an SPSC pair over a ring sized to hold at least capacity_samples interleaved samples (rounded up to a power of two so the index mask is valid). channels is the interleaving width the producer rounds pushes to so a partial write never splits a frame; the caller (rlx-core’s intake) has already validated it.