Nothing seems to be easy in our media world these days. You’d think that if there were captions on a master videotape that it would be easy to transfer them when encoding the tape to a DVD.  But of course, it’s not that simple. Here’s the deal: On a videotape, the caption information is stored as digital information within the vertical interval of a television signal.  You can actually see that signal as a white line if you have a tech monitor where you can shrink the picture (otherwise known as “underscan”) such that you can see the normally hidden vertical interval part of the picture. The closed captioning info is stored on line 21 of the vertical interval.

Line 21 caption information in vertical interval

On-screen “captions”

In regular over-the-air or cable/satellite viewing or digital recorder, the captions are decoded and displayed by the television set.  One turns them on or off by accessing controls on the television.

TV remote

On-screen caption on/off menu

When we make videotape copies of closed-captioned masters, we easily carry over the line 21 closed-captioned information.

But it’s not so simple when we make DVDs from a closed-captioned videotape master.  Yes, we can take your closed-captioned master tape and encode it to a “Line 21 DVD master,” but bear in mind that that can be done only on one of our “pro-sumer” DVD recorders.  Good enough quality for most applications, but still not our highest rez encoding.

Higher level DVD encoders strip the vertical interval signal from a tape thereby not carrying over the closed captioned information to the resulting DVD master.  So, in those cases, an authoring session is required where a special .scc file is blended with the digitized video signal to make a closed-captioned DVD master.  The result is a high-quality DVD master that will in effect act like a Line 21 DVD.  In other words, the captions can be turned on and off via the monitor.  An authoring session is $150/hr plus the “burning” of a DVD approval copy and DVD master.  The above-mentioned .scc file is provided by the captioning vendor.  For a relatively minor fee, they should be able to easily make this flavor of file format from the original caption file.

Another option is to utilize the subtitle function of DVDs.  That requires the same process as mentioned above with the .scc file, with the captioning vendor providing a .stt or other similar file. The advantage of this over a .scc file is that subtitles are often preferred aesthetically to captions, and they can be turned on and off with the DVD remote instead of through the monitor.

DVD remote

On-screen subtitles (no black background)

You may ask what happens when DVDs with either a .scc or .stt file get played in a computer.

Such files can usually be turned on or off via the DVD player in the computer.  For example, Windows Media Player ver. 10 has a pull down menu for that under the Play menu.

(Please note that the operative word there is “usually.”  Some software DVD players struggle playing back subtitles and captions.)

I hope that helps clarify things a bit when it comes to adding captions or subtitles to a program that’s being master to a DVD.

Feel free to leave a comment below.  And of course, contact me at dryan@videolabs.net or 301-217-0000 x104 with any questions.