How to check if element supports transformation

[Nirbheek Chauhan]

Hi Edgar,

The relationship between supported input caps and output caps for an
element is not statically retrievable, since it can often depend on
the device (for hardware elements like glcolorconvert, vtdec,
vaapidecodebin etc), or on library versions (for elements that use
external libs), or on the platform you're running on.

Sometimes you can assume that all output caps are supported for all
input caps, for example with videoconvert. But in general, you will
need to run a pipeline: set the input caps and do a caps query on the
srcpad or vice-versa.

Cheers,
Nirbheek

On Fri, Dec 10, 2021 at 4:45 PM Edgar Thier via gstreamer-devel
<gstreamer-devel at lists.freedesktop.org> wrote:
>
> Hi,
>
> I am looking for a way to check if certain transformations are supported by an element without starting a pipeline.
>
> GstQuery does not seem to support this.
> Manually trying to access transform_caps seems weird.
>
> Is there a way to see what caps I can use as input for given output caps or is trying to access transform_caps my best hope?
>
> Thanks,
>
> Edgar
>