[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

  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
  * 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

* 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

* 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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