On 10/7/15 7:05 AM, florian.he...@rbb-online.de wrote:
Hello everyone,

i'm working on a project where we want to livestream one TV-Program with
MPEG-DASH. There for we need seperate subtitles. The encoder gets the
signal over HD-SDI wich supports embedded subtitles in Teletext with SMPTE
2031.
Our capturecard will be a Blackmagic Decklink Duo wich supports VANC-Data.


I know that ffmpeg can extract closed captions from files. But what about
Livesignals like from SDI-Signals?
Thank you,
Florian


I am currently trying to get the decklink card to output CEA-708 closed captioning, so I can tell you a little about what I know so far. The current driver does not support capture or playback of VANC/closed captioning. The capture does support 10bit as I recall, which is the first thing you would need just to be able to capture the VANC. I don't know anything about SMPTE 2031, but at the very least you would need to ask for the correct DID/SDID for SMPTE 2013 and then place that data in a Teletext stream. That would require a patch to the current ffmpeg.

When/if I get this output to work, I would certainly be willing to try my hand at creating a patch for this. I wish someone out there had a decklink card that could capture live tv in North America. Having some real world data to look at would make creating the CEA 708 output easier...

Deron
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