[vdr] PVRINPUT plugin and "black/cinema bars"

Martin Dauskardt md001 at gmx.de
Mon Apr 26 21:42:09 CEST 2010


> From: VDR User <user.vdr at gmail.com>
> Subject: Re: [vdr] PVRINPUT plugin and "black/cinema bars"

> > I am pretty sure that your TV station broadcasts analogue TV not
> > anamorphic, which means it "delivers" the black bars to prevent the
> > aspect ?ratio of a 16:9 content.
> 
> The 'black bars' are called letterboxing.  It's used to _preserve_ the
> aspect ratio of widescreen content on 4:3 displays, not prevent it as
> you've suggested.
I meant that. Sorry for the mistake, english is not my native language.
> 
> > Unfortunately there is no way to detect the incoming signal (Tuner or
> > extern). Therefore it is not possible to automatically choose the right
> > setting.
> 
> Sure there is, just look in the mpeg headers.  If for some reason that
> flag isn't set correctly, you can also use the resolution along with
> some simple math to calculate the aspect ratio.

The mpeg is not delivered by the broadcaster, it is generated by the encoder. 
The content of the header is a result of the V4L2_CID_MPEG_VIDEO_ASPECT 
setting done by the application. 
> 
> >> Any ideas how to remove these?
> > 
> > The driver does not support clipping/cropping. We will always encode the
> > whole capture size. If there is already a bar, it will also be in the
> > encoded stream. You could try to use the zoom mode of your TV.
> 
> You _could_ write some functions to detect and remove letterboxing,
> though I don't know anyone motivated enough to actually do it.

The main goal of the pvrinput-plugin is to use the hardware encoder.I think it 
is a bad idea to do software-based on-the-fly-recoding.

Simon, which output device do you use? Maybe the xine- or xineliboutput-Plugin 
can do the needed zoom for you. (?)

Greets,
Martin



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