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

Simon Hailes simon.hailes at screen.subtitling.com
Thu Jun 17 00:03:28 CEST 2010

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

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
Main Line : +44 (0)1473 831700 | Ext : 272 | Fax: +44 (0)1473 830078
simon.hailes at screen.subtitling.com | www.screen.subtitling.com

Visit us at Broadcast Asia, Singapore Expo, 15th - 18th June, UK Pavillion, Stand 7H2-12

Before Printing, think about the environment

This message may contain confidential and/or privileged information. If you are not the intended recipient you must not use, copy, disclose or take any action based on this message or any information herein. If you have received this message in error, please advise the sender immediately by reply e-mail and delete this message. Thank you for your cooperation. Screen Subtitling Systems Ltd. Registered in England No. 2596832. Registered Office: The Old Rectory, Claydon Church Lane, Claydon, Ipswich, Suffolk, IP6 0EQ

More information about the vlc-devel mailing list