Function run_spliced_decode_pump_blocking 

pub fn run_spliced_decode_pump_blocking(
    clips: Vec<ClipSource>,
    senders: Vec<Sender<VideoFrame>>,
    rt: Handle,
) -> Result<u64>

Spliced decode pump, designed for tokio::task::spawn_blocking. Decodes each clip in order, drops frames outside the clip’s [start_frame, end_frame) source range (trim), and fans the kept frames out to all senders continuously across clips (concat). Because the muxer numbers output frames by count — not by source PTS — the join is automatically gap-free and the timeline is zero-based, with no PTS rewriting.

If a sender’s channel is closed (its rung gave up) the pump keeps going with the rest; it stops only when every sender is closed. rt bridges into the async send().await. Returns the total number of frames emitted.