Amazon's Prime Video basic ad tier, which began on Jan. 29 in the US as a downgrade to subscribers, quietly cut Dolby Vision HDR and Dolby Atmos sound support (John Archer/Forbes)

John Archer / Forbes:

Amazon’s Prime Video basic ad tier, which began on Jan. 29 in the US as a downgrade to subscribers, quietly cut Dolby Vision HDR and Dolby Atmos sound support  —  Amazon AMZN caused a furor recently when it announced that it was introducing advertisements right across its Prime Video streaming service.