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

Timothy D. Lenz tlenz at vorgon.com
Mon Apr 26 21:06:38 CEST 2010


My local stations here in the US are doing the reverse on all primary 
atsc channels. They add bars to the side for anything that is not wide 
screen to make it wide screen. So 4:3 stuff on my 4:3 tv are in a little 
window because the software then adds bars top and bottom to put it back 
to 4:3 :(.

On 4/26/2010 10:27 AM, VDR User wrote:
> On Mon, Apr 26, 2010 at 12:27 AM, Martin Dauskardt<md001 at gmx.de>  wrote:
>>> Doesn't matter which aspect ratio I choose, every channel under the PVR-500
>>> displays with black (cinema) bars on the top and bottom of the image.
>>
>> 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.
>
>> 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.
>
>>> 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.
>
> Cheers
>
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