[theora] Closed Captioning
dsiebert at eclipsecat.com
Wed Dec 4 09:13:00 PST 2002
In line 21 captioning there are two modes.
Using pop up you have to build the caption in the encoder first then you
pop it at the correct time.
Each caption has a start location and it is specified in row and column
0 at the top 15 at the bottom 0 to the left 31 to the right.
Closed captioning has a very limited bandwidth. About 60 chars a second.
So you can see that for pop ups to work you have to create the caption
before actor says the line. This mode tends to be used for post
captioning of pre-recorded video.
Roll ups are used for live events and some prerecorded video. When text
is sent it is displayed and it rolls up. When you go into roll up mode
you have to tell it what row to start on and you have to move the
captions to clear things like Sports Scores and Telephone numbers.
BTW if you want to know how they caption live events it all starts with
a court reporter writing on a steno machine. Then our program
translating that steno into English then sending it on to an encoder
usually via a 1200 baud modem. The reason for the old slow modems is
that is what the encoder have built into them and a lot of them will not
work with new modems!
You also have to mix the modes.
I would love to see a streaming format that handles captioning well.
Ralph Giles wrote:
> On Wednesday, December 4, 2002, at 02:29 pm, Carsten Haese wrote:
>> Would that design be flexible enough to be usable for storing lyrics in
>> a Vorbis stream, too?
> That's the idea. The hard part is actually finding a format flexible
> enough that you can print transcripts from it. Lyrics are pretty
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