[MEncoder-users] ATSC closed captioning

[Scott W. Larson]

Reimar Döffinger <Reimar.Doeffinger at gmx.de> wrote:
>Roll-up support exists in SVN, on top of what your patch does also
>4-line roll-up and roll-on mode.

Ah, someone added a scroll buffer. Good idea. I bet a lot of other bugs I worked around are fixed as well. I don't see support for italics but enclosing the text in '<>' was the only idea I could come up with.

>And btw. the second channel is in the second field, which both your
>and SVN code discard.

In ATSC, captions are in the picture user data, not in the video. The EIA-608 data is tagged as either channel one or two. Yes there's no way to select which channel to display. So far I have not found any captions in the second channel of any ATSC broadcasts (only XDS data) so this wasn't a problem for me. This situation could change of course. Once Mexico starts converting to ATSC we can expect them to include both English and Spanish closed captions. It's likely that the English ones will only be available in the CEA-708 subtitles.

>However the biggest problem I have is the subcc_decode function in
>SVN which claims to do EIA-708 but has not resemblance at all with it.
>I suspect it might be CC-subs for DVDs and maybe they are different,
>but it seems we do not have a single sample for that...

There is a passing reference in the comments to "the EIA-708 standard" but nothing that says it supports them. MythTV has incomplete support for CEA-708 captions but it doesn't work very well and they recommend displaying the EIA-608 ones instead.