[mythtv] Patch to autodetect 4:3 Zoom aspect ratio

[Brad Templeton]

> Chris - good thoughts, but wouldn't this be a problem for LiveTV?
> Also, sometimes you want to watch commericals (i.e., superbowl) and
> some are filmed in letterbox and some in 4x3.  In both those cases,
> wouldn't the autodetection have to be dynamic enough to basically do
> real-time analysis? The commerical detection code doesn't do anything
> besides find commercials, so it definitely could work for that short
> period of time.
> 
> Another use case I've found from time to time is that content within a
> 16x9 program will sometimes deliver 4x3 content randomly.  I think
> Extreme Home Makeover does that, along with several documentary type
> shows.
> 

Yes, there is a lot of variation.  Of course you will regularly
see 4:3 commercials in widescreen content, and you even see 16:9
(letterbox) commercials mapped into 4:3, and then re-mapped to 16:9
to give both the letterbox (top/bottom bars) and pillarbox (side bars.)

Now I personally don't use zoom much on SDTV letterbox because it
exposes the pixels and other inadequacies of SDTV too much.

However, there is another useful application of pillarbox/letterbox
detection.   That would be to have the OSD aware of this detection,
and have it move the OSD information  into the black bars, so that
they do not cover the program.    Likewise the captioning engine.
Indeed, in that situation you could also code a "full time" OSD
for use in this situation.   (Right now the OSD engines are done
into the video window so they can't easily go into the myth
generated pillarbox of SDTV, or at least that was the case last time
I looked.)