question how to add own customized element between source element and decodebin2 element when using playbin2

[bcxa sz]

Hi Developers,

Here we want to do something special between source elemet and
decodebin2 element with playbin2.

For example, when playback one avi file from harddisk, we have one own
element called routine element, And we prefer to let it stay between
the file source element and decodebin2 element to do something
special.

But I don't how to make it inserted by playbin2 when playbin2
construct the pipeline.

best regards

BCXA