Changing width/height properties from within plugin

[Karol-2]

Hello,

I'm trying to write trivial plugin that does image rotation (90, 180,
etc. degrees).  My question is - where should I change "width" and
"height" properties?  I thought the proper place would be _chain()
function(*) where I deal with buffer contents.  However, pipeline dies
with internal error if I do that.  I guess I should handle that
mysterious beast called caps negotiation? (specifically: _set_caps()
function?)

(*) I'm using basic GstElement, not GstBaseTransform.

Thanks in advance.


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[Stefan Sauer]

Am 24.02.2010 18:09, schrieb Karol:
> Hello,
>
> I'm trying to write trivial plugin that does image rotation (90, 180,
> etc. degrees).  My question is - where should I change "width" and
> "height" properties?  I thought the proper place would be _chain()
> function(*) where I deal with buffer contents.  However, pipeline dies
> with internal error if I do that.  I guess I should handle that
> mysterious beast called caps negotiation? (specifically: _set_caps()
> function?)

If you can't use videflip, you can at least look how it is done there.

STefan

>
> (*) I'm using basic GstElement, not GstBaseTransform.
>
> Thanks in advance.
>
>
> ------------------------------------------------------------------------------
> Download Intel® Parallel Studio Eval
> Try the new software tools for yourself. Speed compiling, find bugs
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[Karol-2]

On Fri, 26 Feb 2010 10:04:03 +0200, Stefan Kost wrote:

> Am 24.02.2010 18:09, schrieb Karol:
>> Hello,
>>
>> I'm trying to write trivial plugin that does image rotation (90, 180,
>> etc. degrees).  My question is - where should I change "width" and
>> "height" properties?  I thought the proper place would be _chain()
>> function(*) where I deal with buffer contents.  However, pipeline dies
>> with internal error if I do that.  I guess I should handle that
>> mysterious beast called caps negotiation? (specifically: _set_caps()
>> function?)
>
> If you can't use videflip, you can at least look how it is done there.

Well, yes.  I've looked at it already and implemented _transform_caps()
in similar fashion.  However, why I needed to explicitly set "width" and
"height" for caps when I wasn't any doing rotation/transformation is
still puzzling to me.

While I don't understand why it happens that way - it does work.

Thanks.


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