EIA-608 Closed Caption Problem

My company currently uses many different Black Magic cards including but not limited to the Decklink SDI and the Decklink HD Extreme.

We need to be able to pass EIA-608 closed captions through the card, into an SDI to Analog mini converter and finally into a TV via the AV video port.

In an attempt to understand the decklink SDK and EIA-608 closed captions I changed the code in the VancOutput.cpp. Since this is the official SDK I feel it should serve as a good baseline for my development, however I have had no success displaying the closed captions on the TV.

For our software to continue to use decklink devices it is of the highest priority that I get this to work. Once I can prove that the VancOutput example works with 608 closed captions I can move on to the real coded solution.

I have uploaded a copy of the code file, according to the email support I received from Blackmagic developer support the code looks correct however it still continues to only display a blue screen without subtitles.

I have tried every closed caption channel, CC 1-4 and Text 1-4, without any luck.

Am I missing some important key factor?


Regards,
Nick Hanshaw

Hi Nick,

Any luck with this? I have a similar situation that requires CC output on Linux (608 and 708 possibly). It seems like a seriously basic part that should already be done and documented!

If you have resolved this, I would appreciate knowing how. If not, then I'll dive in and see if I can't find something wrong. I probably know less than you about this, but having a second set of eyes can help.

Deron

Sorry for the late post.

608 is not a possibility in the vanc as far as I can tell. Focus your efforts on 708.

We broke down and bought a DE285 vanc monitor device from EEG which was key in making this work, otherwise you are just flying blind.

I sent valid 708 closed captions through the DE285, verified the packet structure and compared to our own packet structure, then fixed the issues in the code.

The DE285 was our Rosetta stone, if you don't have a vanc monitor I suggest getting one.

I can definitely tell you that the Blackmagic cards pass 708 closed captions just fine, you just have to be sure your packet structure is correct.


Regards,
Nick

No problems. This is a project for ffmpeg, and no money atm for such things. I'm happy to have rounded up all the various SMPTE/CAE/ACME documents! Anyway, I figured out enough to know that your initial posts were way off the mark! I've got a few small vanc capture examples, and I think I've rounded up someone who can capture some additional real life data using a KTECH(?) receiver and a Decklink. Hopefully that will be enough. Just a few things about the structure I'm not sure about but that is always going to be true.

Glad to hear you got it sorted out, and thanks for the info.

Deron