Function check_demuxer_seek 

pub fn check_demuxer_seek<D, F>(
    make: F,
    file: &[u8],
    targets: &[SeekTarget],
) -> Conformance
where
    D: Demuxer,
    F: FnMut() -> D,

Verify a demuxer’s seek against targets.

After the headers, each target is sought (stepping through SeekStatus::Scanning until Seeked). Checked: the reported position is the next packet’s actual timestamp and random-access evidence, never the request echoed back; a RandomAccessPoints seek lands on a packet the container marks RandomAccess::Yes.