[mythtv] Ticket #4872: Detect if video is letterboxed and switch to corect fill mode

[Petr Stehlik]

Willy Boyd wrote:
>>  For me, the "default zoom: half" does not work as expected because it is
>>  zooming even contents that would fit perfectly on screen without any
>>  black bars - i.e. 16:9 movie on 16:9 screen is zoomed as well. The
>>  default zoom should IMHO zoom to half (if enabled) only if the movie is
>>  4:3 and screen is 16:9 (not sure about 16:9 movie on 4:3 screen).
> 
> I thought that "half" only specified how much to zoom?  Even if the
> video is 4:3, it may be displaying a 16:9 movie or show with the black
> bars encoded into the stream.  Zooming in on this is what this feature
> enables.

Well, I meant it differently - normally the "remove black bars" function 
never "overscans" but with 4:3 movie on 16:9 screen there is a lot of 
wasted screen space due to the black bars so I thought it would be cool 
to automatically zoom in to 14:9 (called also half zoom) to partially 
overscan and partially remove the black bars.

I realize it has not much common with the autodetect function but it 
fits under the feature "remove black bars" :-)

So it would work as follows:

if (black bars in stream detected)
     zoom as much as possible to remove the black bars;
else
     if (video aspect ratio != screen aspect ratio)
         if (half zoom allowed)
             set half zoom to remove at least part of the black bars;


Currently it seems to miss the aspect ratio compare condition.

Petr