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

mythtv at longhome.co.uk mythtv at longhome.co.uk
Mon Mar 10 20:20:28 UTC 2008

> On Sun, Mar 9, 2008 at 12:32 PM,  <mythtv at longhome.co.uk> wrote:
> > I've noticed that 2.39:1 letterboxed in a 16:9 stream also gets
> zoomed,
> >  meaning part of the broadcast picture is lost. I would have thought
> that
> >  only content in a 4:3 stream should be zoomed? Right?
> >
> That is strange because I test if width/height <= 1.5. And that is the
> width and the height of the frame I am processing. So it should not do
> anything about streams in 16:9.
> What kind of stream is it? Is it possible that it starts in 4:3 and
> then switches to 16:9?

[Martin Long] 
Hmmm... it's interesting. As far as I know pixels in UK freeview are not
always square, but sometimes are. 

So, sometimes the same resolution is used for 16:9 and for 4:3 - meaning
ratio is not a viable means of detecting aspect ratio. I'm not sure what the
signalling mechanism is that's used, but this must be available to myth, as
it seems to display at the correct aspect. 

I'll see if I can dig around a bit in the code, and try and grab some
resolution examples for you. Unfortunately I'm working a lot of hours at the
mo, so it might be a little while. 


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