/** Our subtitle streams have colour maps, which can be changed, but
* they have no way of signalling that change. As a hack, we have this
* method which callers can use when they've modified one of our subtitle
/** Our subtitle streams have colour maps, which can be changed, but
* they have no way of signalling that change. As a hack, we have this
* method which callers can use when they've modified one of our subtitle