[FFmpeg-user] Export Subtitles live from HD-SDI
deron at pagestream.org
Wed Oct 7 17:31:32 CEST 2015
On 10/7/15 7:05 AM, florian.hesse at 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
> 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,
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...
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