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Originally Posted by spiderplant
Props (or whoever): I ought to know the answer to this, but don't. How does audio description actually work? Is it a second audio stream that gets mixed with the normal audio, or a complete replacement stream? What is the stream_type?
Nini's second post may be a clue. I'm off to set my Freeview box to Welsh to see what happens.
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Theres a second audio PID, and a reference to it in the PMT, which is just a voiced commentary of what is going on. Its lower bitrate, as theres only the voice and I think its mono.
I remember a second box that needed to used in conjunction with the DTT box which gave the audio out, but apparently newer boxes allow you to select the voiced track instead.