need Candadian visa or not?

Vancouver airport has two routes:
1. follow the sign "To USA": DON'T need candadian visa, after collect your luggage, follow the sign "To USA". will be checked by US immigration and customer officer just like any US port of entry airport, it is "domestic" flight(s) from now on(no check any more, you already entered US at Vancouver airport)

2. NEED Canadian visa: after collect your luggage, proceed to canadian immigration/airport exit. even though you will check in at the airliner counter and get back into the airport again.