This paper from Evertz may be helpful.
http://www.evertz.com/resources/cc-imp-paper.pdf
Basically, CC data is RECORDED in HD recorders in the VANC (Video
Ancillary Data) area of the SDI bitstream. This area is not "visible"
on the screen as older line-21 encoded CC is. It is just "data" and is
passed along in subsequent recordings.
Now, when this video is BROADCASTED in an ATSC DTV broadcast, this CC
data is encoded into a special area of the ATSC bitstream, which is
different than the SDI stream recorded on the master tape. Same data, I
think. Just a different packaging.
I THINK this is how it works, on a technical level.
The workflow is pretty much the same as when doing normal CC work. The
master tape is fed through an encoder, which inserts the data into the
VANC and the result is recorded on another deck. This signal is played
through a decoder, which then displays the results.
Ed at PMI
Pittsburgh, PA
USA
-----Original Message-----
From: owner-ds(at)Softimage.COM [mailto:owner-ds(at)Softimage.COM] On Behalf
Of Keuler, Bob
Sent: Monday, October 03, 2005 10:30 AM
To: DS(at)Softimage.COM
Subject: RE: hdcam close captioning q
Hi Jef,
All I can tell you is that we recently had a CC HD Master made. I
watched the tape in SD through the HDCam D-Converter and did not see a
CC Signal! Did the facility forget to CC the master? Is the HD CC signal
recorded in a different manner than in SD? Does the HDCam D-Converter
board blank the Vertical Interval? Could there also be an issue going
from HD 1080i to SD Letterbox and the captioning not working? So far,
I'm guessing we would need to have SD versions made with CC as the CC
would get lost in the D-Convert. I'm looking into it but I thought I'd
just give you a heads up.
Bob Keuler
Senior Avid|DS Editor
WLIW Productions
450 West 33rd St. (7th Floor)
New York, N.Y. 10001
(212)560-8843
keulerb(at)wliw.org
-----Original Message-----
From: owner-ds(at)Softimage.COM [mailto:owner-ds(at)Softimage.COM] On Behalf
Of Jef Huey
Sent: Monday, October 03, 2005 10:13 AM
To: DS(at)Softimage.COM
Subject: hdcam close captioning q
Anybody out there with a bit of experience delivering close captioning
on HDCam tapes?
I have some workflow questions.
Thanks,
Jef
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