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

[Mårten Bohlin]

On Mon, Feb 25, 2008 at 2:17 PM, Mårten Bohlin <mabo at mochc.net> wrote:
> On Fri, Feb 22, 2008 at 4:06 PM, Mark Kendall <mark.kendall at gmail.com> wrote:
>
> > On 22/02/2008, Mårten Bohlin <mabo at mochc.net> wrote:
>  >  > Hi!
>  >  >
>  >  >   I have written a patch for the release-0-20-fixes branch (svn
>  >  >   revision: 16162) that detects black bars on the top and bottom of the
>  >  >   frames. When that is detected it toggles to "Letterbox 4:3 Zoom". And
>  >  >   if no bars is detected it toggles back to "Letterbox Off".
>  >
>  >  >   Comments are welcome.
>  >
>  >  Mårten
>  >
>  >  What about material that is (for example) 2.35:1 displayed on a
>  >  widescreen (16:9) display? (i.e. 'super' widescreen dvds) If you
>  >  updated your patch for trunk, you would apply the correct 'zoom'
>  >  (either half or full) but the scan lines you're using may not work
>  >  (i.e. they might still fall within the actual content - though I
>  >  haven't checked).
>
>  I have not tested with content 2.35:1 content, but if it does not work
>  as it is there is just som minor adjustments of the limits to get it
>  to fill to full zoom.
>
>
>  >
>  >  Also, is the letterbox detection robust enough? As far as I can tell,
>  >  it's taking a very  limited sample set and doesn't check for
>  >  consistency within the 'actual' frame content. So how would it react
>  >  to a dark sequence for example? Would it be better to check for 'dark'
>  >  letterboxing and 'non-dark' content?
>  >
>  >  My apologies if my quick scan of your code has missed something.
>  >
>  >  Regards
>  >
>  >  Mark
>  >
>  >
>  > _______________________________________________
>
>
> Yes it only looks at two lines on the screen for performance reasons,
>  but it also checks that it seems to be vertical lines on the top and
>  bottom of the screen before it makes a switch to the detected zoom mode. So yes
>  I find it very robust, I have used it daily for over a week now and are happy with it.

I meant horizontal lines. Not vertical.

>
>  It only switches if it finds out that it should switch in 3 frames in
>  a row.

And here I meant three consecutive frames. ("in a row" is a Swedish expression)

/Mårten