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Closed Caption Edit Question

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Erik Speer
Closed Caption Edit Question
on Dec 8, 2008 at 5:24:17 pm

Hi,

If I digitize a close captioned show will I loose the captioning when I make video only insert edits or will it stay on the tape?



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Mark Suszko
Re: Closed Caption Edit Question
on Dec 8, 2008 at 5:48:23 pm

I was able to capture into my Discreet Edit*6 in composite format, make cuts to shorten the captured footage, and play back out preserving the cc data. If you ADDED new footage, what I expect would happen is, the line 21 captioning would drop out where the new footage came in, leaving some garbled remainder frozen on the screen super, and then pick up after that point when you got back into the old footage, but that re-entry would probably be a little garbled as well, until the cc data got refreshed and "caught up" to the encoder.

The cc signal is recorded on the line 21 vertical interval portion of the video signal, in NTSC SD video, so any edit of the video also destroys the caption data in that segment. When we go to digital, I have no idea where that data is kept in relation to the video, it is now some kind of metadata, but I suspect it is still matched to the original picture and will not "stick" if you insert new shots.

Reading between the lines of your question, my opinion is you'll have to re-caption the new master after you make your new edits.


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Erik Speer
Re: Closed Caption Edit Question
on Dec 8, 2008 at 5:52:19 pm

What we need to do is take old versions of our shows and update some of the graphics so basically we have to recapture the show, find the spots that need new graphics and replace that shot then go back to tape when all is said and done. This all going Betacam to DVCam.



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Dino Sanacory
Re: Closed Caption Edit Question
on Dec 8, 2008 at 10:02:19 pm

As Mark mentioned, captions are recorded in line 21 of standard definition video. This is the first line of active video after the horizontal blanking. If you have a monitor with underscan function, you can see this data a series of short white lines that dance around the top of the frame.

To preserve the captions, you need to digitize the existing material, place the new graphics in under it and then wipe or mask in the top of the old image so the captions are now on the new image. You should have a monitor that decodes captions to check your work on.

I think if you capture your original source as DV, the caption data might be lost as DV clips the first couple lines. I don't know how any particular NLE handles this. I believe that most DVCam recorders can repackage captions by placing the data elsewhere. This requires feeding the deck as analog or SDI.


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Mark Suszko
Re: Closed Caption Edit Question
on Dec 8, 2008 at 10:12:32 pm

If you mixed everything live thru a composite switcher in linear fashion, instead of editing it NLE perhaps this would perserve the line 21 data, don't know for certain, I'd have to know if the switcher strips the line 21 or not. And most people don't own a linear edit controller anymore.


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Michael Hancock
Re: Closed Caption Edit Question
on Dec 9, 2008 at 12:45:40 am

What NLE are you using? That will tell you whether you can retain the CC info.

However, if you're dumping to DVCam, I don't think it will retain the info regardless of the NLE. DV requires a different kind of CC than Beta (I believe), since Line 21 is cropped (720x486 analogue versus DV's 720x480), as someone already mentioned.

Michael.



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Tim Ward
Re: Closed Caption Edit Question
on Dec 23, 2008 at 2:36:42 am

Dino's got it. Do what he says. If you capture and edit in D1 resolution, then output to dv over sdi or analog. CC will be there.


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