x <- "[Bridge]\r\r\n\r\r\n SPOCK: Check the circuit. \r\r\n [Pike's Quarters \r\r\n BOYCE: Boyce here.\r\r\n"
x <- gsub("\\[[^]\r\n]*(?:]|\\R)", " ", x, perl=TRUE)
x
eCA8LSAiW0JyaWRnZV1cclxyXG5cclxyXG4gU1BPQ0s6IENoZWNrIHRoZSBjaXJjdWl0LiBcclxyXG4gW1Bpa2UncyBRdWFydGVycyBcclxyXG4gQk9ZQ0U6IEJveWNlIGhlcmUuXHJcclxuIgp4IDwtIGdzdWIoIlxcW1teXVxyXG5dKig/Ol18XFxSKSIsICIgIiwgeCwgcGVybD1UUlVFKQp4