the command line describing the pipeline
Return: a new element on success, %NULL on failure. If more than one toplevel element is specified by the @pipeline_description, all elements are put into a #GstPipeline, which than is returned.
GException on failure.
Create a new pipeline based on command line syntax. Please note that you might get a return value that is not %NULL even though the @error is set. In this case there was a recoverable parsing error and you can try to play the pipeline.