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

Björn Stenberg bjorn at haxx.se
Mon Jun 21 16:02:59 CEST 2010

simon h wrote:
> A decoder in the process of acquiring the
> service can rely on the region_n-bit_pixel_code being the current region
> fill colour regardless of the state of region_fill_flag."
> This indicates that the fill flag is designed to be set once to cause a
> fill, and then cleared.  If a decoder acquires the service and a region is
> 'new' to the decoder, it should fill with the existing colour.

Yes, but that section discusses how a decoder acts when acquiring the service. Page state "normal case" is not an acquisition point, so it does not necessarily apply.

However, I struck gold in point four of "5.1.6 Points to note":

  "A decoder shall inspect every RCS in the display set to determine if the
   region is to be modified, for example, which pixel buffer modifications are
   required or where there is a modification to the associated CLUT family. It
   is sufficient for the decoder to inspect the RCS version number to
   determine if a region requires modification. There are three possible
   causes of modification, any or all of which may cause the modification:

   - region fill flag set;

   - CLUT contents modification;

   - a non-zero length object list."

This removes all doubts in my mind. You were right, I was wrong. I thus retract my patch suggestion.

Thank you.

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