[mythtv-users] special chars in epg data

[Michael T. Dean]

On 03/21/2008 12:19 PM, Markus Schulz wrote:
> some of my channels have some special unicode chars in their epg data 
> (mostly: 0x05, unicode=UPWARDS WHITE ARROW # Shift key).
>
> Is there currently (=trunk) a way to get rid of them?
>
> I think in most fonts these characters are non-printable. 
> Perhaps there is a way to check this for the selected OSD-font and 
> discard such chars.

I wrote a patch that skips pre-caching of images for the C0 and C1 
control codes ( http://en.wikipedia.org/wiki/C0_and_C1_control_codes ).  
The patch was committed in [13612] ( 
http://svn.mythtv.org/trac/changeset/13612 ) so it's in both 0.21-fixes 
and trunk.

What I did not do with that patch was to prevent them from being 
rendered/cached when explicitly used by the captions.  You could easily 
modify the code to cache a zero-width image for those (and/or other) 
non-displayable characters.  If a reference to a zero-width (zero-size?) 
image was instead pre-cached for those characters, they'd be rendered 
invisible (invisibly? ;).

However, it's quite likely that if these characters appear in the 
stream, they're actually supposed to be handled by the caption decoder.  
I haven't read the specs for EIA-608/708 captions, so someone else could 
likely give you better info.  The main reason I'm mentioning this is 
because if they are supposed to be handled, a "workaround" patch like I 
mention above is unlikely to be accepted.  To handle them appropriately 
(whatever appropriately means), you'd have to modify 
libs/libmythtv/cc[67]08decoder.{h,cpp} .

Also, if you're not positive what character you're seeing, you may want 
to use the patch I'm attaching, which is a hack I've been using for a 
couple of years to identify characters in captions that don't exist in 
my caption font.  The only character I'm seeing regularly requested, but 
for which there is no glyph in my caption font is 0xa (linefeed), and I 
almost always enable captions.

Mike


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