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

Mårten Bohlin mabo at mochc.net
Tue Feb 26 15:12:38 UTC 2008

On Tue, Feb 26, 2008 at 3:09 PM, aaron <memoryguy at gmail.com> wrote:
> On 2/25/08, Mårten Bohlin <mabo at mochc.net> wrote:
>  >
>  > Hi!
>  >
>  > I have now updated my patch to the release-0-21-fixes branch (svn
>  > revision: 16236). It now switches between automatically between the
>  > fill modes "Full" and "Off".
>  >
>  > If this patch is a candidate to go into a future release I could make
>  > it possible to turn the auto detection on and off from the playback
>  > settings.
>  >
>  Hi,
>  I gave this a whirl last night on SVN trunk (which I think would be
>  close enough to 0-21-fixes) and I think it said it applied cleanly,
>  but when I watch a recording it doesn't do anything. Have I forgotten
>  to do some extra step? I was under the impression it should be enabled
>  by default?
>  I did see that there is a new, selected, option in the Adjust Fill
>  menu, "Autodetect", so I assume at least part of the patch worked ;-)
>  I didn't get to play with it much last night because it was late and I
>  needed to get to bed. I'll try to play again tonight.
>  My source is only analog cable, which I believe is always broadcast in
>  4:3. Thus, I get pillarboxing all the time (bars on the sides) on my
>  widescreen TV. Sometimes shows are letterboxed, which is embedded in
>  the broadcast. That's where the Fill mode is useful. As I understand,
>  your patch should detect these shows and adjust the Fill Mode setting
>  automatically. Am I right?
>  I saw that the patch has some "playback" verbose logging, so I'll try
>  turning that on and see what it says.
>  I also noticed that at least some shows have the station logo
>  overlapping the black bars. I wonder if that could be what's throwing
>  off the detector?
>  In any case, this patch looks promising, and is certainly a nifty
>  little feature I'd love to have :)
>  --
>  aaron
>  "Oh oh oh. I'm incoherent with excitement. Please tell me what fascinating
>  bit of badger-sputumly inconsequential trivia you will assail me with next."
>         -- Arthur Dent

Yes it should be enabled by default and the logos should in most cases
be outside of the detection area. But I had to adjust the detection
limits a couple of times to get it to work with all of my channels. So
my guess that it is some more adjustments to e done. For instance your
black bars might not be black enough.

If you could make a sort recording that I could download, I could have
a look at it. (If you dont make the adjustments yourself).

If you do not get any output with the verboseflag you could try to
switch to half zoom and then activate the autodetection again from the
menu. That should make it to switch to either Off or Full and then log
why it did that.

I am also thinking about adding a debug mode where you get visual feed
back on where it has detected the letterbox edge, and where the limit
to switch to a diferent mode are.


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