Would like closed caption expert to answer a few questions

[jimdagys]

I am using the Ematic on- air digital TV recorder (from Walmart $30-$40). I'm interested in extracting good srt subtitles and I think I've figured it out with the help of comment #7 CC Extractor. The situation is that sometimes when I record TV programs, the extracted subtitles (using CC Extractor v.65) are perfect. Other TV programs on the same channel, however have subtitles that repeat in a strange way.
Even if I delete (for example) even or odd subtitles, the result still has some repeating of words. However, if I tick "For roll up captions, don't duplicate lines..." (see screenshot, red circle), then the subtitles appear to be perfect. Question #1 Can someone explain why the same TV station has 2 different kinds of caption protocols? Question #2 And what does "roll up captions" mean? Any additional comments on this topic to further clarify what is going on would be helpful. I have attached a sample recording ( W2 5MB) and two extracted srt files. Subtitle W1 is the default setting of CC Extractor which gives repeated words. Subtitle W2 is correct by ticking "For roll up..." in CC Extractor.
I have also attached the original ts file (from the digital recorder) which is used with CC Extractor to get the subtitles.

[KarMa]

Roll up subtitles will appear a character at a time on the TV screen, as if someone were typing out the words in real time. And then when that line is completed, it will rise up a line, making room for the next line to appear. As apposed to having all the text showing up at once.

I guess when the CC decoder finds duplicate lines, it knows to display them in this roll up fashion.

Update: All the TV station has to do to switch between normal CC and roll-up CC is whether or not there are duplicate lines. When there are duplicate lines, that triggers the decoder to do roll-up. Their rational for switching between the two is up to the producer I guess, what they think the audience would prefer.

[usually_quiet]

Update: All the TV station has to do to switch between normal CC and roll-up CC is whether or not there are duplicate lines. When there are duplicate lines, that triggers the decoder to do roll-up. Their rational for switching between the two is up to the producer I guess, what they think the audience would prefer.

Somebody connected with the show or the captioning service must decide which style to use, and it can change periodically. I have been recording one program for my sister for some time. I pay attention to the closed captions because she loans her discs to a friend who has some hearing loss. Previous seasons (most of which are still being repeated in rotation with the latest one) have roll-up captions, but the current season does not.

[KarMa]

I know NBC Nightly News does roll-up along with PBS Frontline and CBS Sunday Morning.

[pashok326]

Hey guys. I have a problem with Roll-Up mode.
I tick "For roll up captions, don't duplicate lines..." and extract subs from ts-file,
but this function didn't work and duplicate lines remained in place.
Tell me what else I can do?
All files attached.