[theora] Closed Captioning

[David Siebert]

In line 21 captioning there are two modes.
pop up
and
roll up

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 
> straightforward.
>
>  -r
>
> --- >8 ----
> List archives:  http://www.xiph.org/archives/
> Ogg project homepage: http://www.xiph.org/ogg/
> To unsubscribe from this list, send a message to 
> 'theora-request at xiph.org'
> containing only the word 'unsubscribe' in the body.  No subject is 
> needed.
> Unsubscribe messages sent to the list will be ignored/filtered.
>
>

<p>--- >8 ----
List archives:  http://www.xiph.org/archives/
Ogg project homepage: http://www.xiph.org/ogg/
To unsubscribe from this list, send a message to 'theora-request at xiph.org'
containing only the word 'unsubscribe' in the body.  No subject is needed.
Unsubscribe messages sent to the list will be ignored/filtered.