Closed Caption in Digital TV - How?

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spellkaw
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Joined: Mon Oct 10, 2016 12:36 am

Closed Caption in Digital TV - How?

Post by spellkaw » Mon Nov 06, 2017 12:52 am

Hi,

there is a new law in our country to include closed caption in TV broadcast.
how do this closed caption works? is there a diagram or solution that we can follow?
or the strategy varies per TV operators?

Thanks.

w9wi
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Joined: Tue Feb 05, 2008 11:40 am
Location: Pleasant View, Tennessee
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Re: Closed Caption in Digital TV - How?

Post by w9wi » Mon Nov 06, 2017 7:06 am

What is the digital TV standard in your country?

In the USA the EIA-708 standard is used for captions. In practice captions are found in the ancillary data of the SDI video stream and encoded into the video stream in the MPEG-2 encoder.

I would start by checking the specifications for your MPEG encoders. I see captions are done a bit differently in DVB-T (apparently they constitute a separate elementary stream) but if I had to guess I'd say the MPEG encoders are still responsible for encoding them.
--
Doug Smith W9WI
Pleasant View, TN EM66

spellkaw
Posts: 11
Joined: Mon Oct 10, 2016 12:36 am

Re: Closed Caption in Digital TV - How?

Post by spellkaw » Tue Nov 07, 2017 3:43 am

Thanks Doug! actually we adopted the Japanese ISDB-T standard.
Our encoders support both 608 and 708 and the selection setting is kinda straightforward.
But where do we encode the closed caption text? is it on the editing machine like for example we are using adobe premiere?
or do we need to buy a separate machine for closed captioning?

Thank you.

w9wi
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Joined: Tue Feb 05, 2008 11:40 am
Location: Pleasant View, Tennessee
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Re: Closed Caption in Digital TV - How?

Post by w9wi » Tue Nov 07, 2017 4:45 am

Ah.

I don't know of any way to do it on the editing machine. You do need a separate caption encoder. I Googled on "ISDB-T caption encoder" and found this:
http://www.eitv.com.br/en/produtos/wohl ... ecoder-cc/

This one is for Brazil; I'm not certain it will be correct for other countries.
--
Doug Smith W9WI
Pleasant View, TN EM66

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