In one aspect, an example method for outputting an alert indicating a functional state of a back-up video-broadcast system involves a computing device receiving first closed-captioning data that corresponds to a first video-stream; the computing device receiving second closed-captioning data that corresponds to a second video-stream; the computing device making a determination that the received first closed-captioning data and the received second closed-captioning data lack a threshold extent of similarity; and responsive to the determination that the received first closed-captioning data and the received second closed-captioning data lack the threshold extent of similarity, the computing device outputting an alert.