Building pipeline dynamically after uridecodebin

[stic at free.fr]

Hi gstreamer friends :)

I am having a custom pipeline reading an incoming stream with uridecodebin.
The stream has video and can optionally have audio too.
I am trying to build the pipeline dynamically (after uridecodebin) depending on audio availability because in the case I immediately build the whole pipeline with audio elements when the incoming stream doesn't have audio then the pipeline won't link.

I am checking audio availability by reading the caps from the pad in the "pad-added" callback of the uridecodebin element.
If audio caps is found then I try to add and link audio elements to the pipeline.
But it doesn't work very well.

What is the proper way check audio availability and then add/link the audio elements dynamically ?

Thanks for any help.