[vlc-devel] [PATCH] cc: Only reset line position if rollup mode changed

[Francois Cartegnie]

Le 23/07/2018 à 14:56, Devin Heitmueller a écrit :
>> I can't be sure if the command should be ignored, or only committed on
>> another one.
> 
> IIRC, the changing of the rollup shouldn’t actually clear the line.  I believe the WGBH reference stream actually demonstrates that case where the rollup is changed to some other value and it isn’t supposed to clear the existing captions.  That said, I haven’t really tested this use case and while this patch improves the situation considerably (the captions go from “completely unwatchable” to “pretty good”) there may be other improvements/fixes which are warranted.

Changing the rollup does not clear any line. The chars just get
rewritten because the cursor resets.

Rollup command should "Precede each new row of text".
The issue is WGBH not following the spec as per B.8.1 where RU commands
should be followed by PAC.

"To continue painting the current row, assuming the relocation occurred
in the middle of a row, the PAC used should indent to the same column
number where the cursor resided prior to the move or to the nearest
indent to the left of that column."

BTW, the 708 decoder has no issue as all with the 708 encoded version.
Wondering if that goes under the radar because US devices use 708 by
default.

-- 
Francois Cartegnie
VideoLAN - VLC Developer