[vlc-devel] [PATCH] dvbsub.c : Don't fill region if page_state == 0

[Simon Hailes]

> I've been working a little with DVB subtitling and found that if the
region_fill 
> bit is set, vlc always fills the whole area on every region update and
thus 
> overwrites any data previously rendered. This behaviour breaks "live"
subtitling 
> where words are recieved one at a time and added to an existing
region.

This is correct behaviour.  region_fill is set only when you *want* the
region to be cleared to the specified background colour.
If the next packet wishes to add to the region, it does not specify
fill, and includes only the new object ID in the rcs.  The existing
objects have already been rendered and remain in the pixel buffer.

> My interpretation of ETSI EN 300 743 is that the region_fill_flag of a
> region composition segment should not cause the region to be filled
> when the containing page composition segment has its' page_state
> variable set to 0 (page update).

If you ignore region_fill for page_state 'normal' (0), then you can't
clear/fill a region without an acquisition point or mode change (except
by covering it with other blank objects :) ).



Simon Hailes | Screen Subtitling Systems Ltd | Chief Technology Officer
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