[mythtv-users] ATSC caption question
Yeechang Lee
ylee at pobox.com
Tue Dec 22 18:10:22 UTC 2009
I've been testing Taylor Ralph's patches to EIA-708 support (#7739,
#7775, and #7776). As he says, they do indeed finally make ATSC
captions usable. A few questions/observations:
* In what situations would using ATSC captions over VBI (which I'd
used until these patches) be preferable, if both are available? I
know ATSC supports color foregrounds and backgrounds, and multiple
typefaces, but are such feature ever actually seen in the real
world?
On the other hand, during the past couple of days using Taylor's
work I've found a few situations in which VBI captions are
preferable to ATSC:
* A PBS program with almost-completely corrupt ATSC but intact VBI
captions.
* A movie in which, during dialogue, VBI captions' positions vary to
indicate who is saying what but ATSC captions don't. VBI captions
sync with dialogue more accurately, while ATSC captions tend to
appear/disappear much more quickly at the end of the lines they
depict.
* I enable black backgrounds for captions for visibility. VBI
captions' backgrounds cover the letters and no more. ATSC captions
apparently reserve a fixed amount of screen space and so their
backgrounds cover more than just the words on the screen at a given
moment.
* VBI captions depict musical notes properly while ATSC captions show
square boxes (an issue fixed with VBI captions some time ago). I use
the same fonts for both so it can't be a font issue.
--
Yeechang Lee <ylee at pobox.com> | San Francisco CA US
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