Created attachment 202596 [details] [review]
pipeline: only have a top-level pipeline do pipeline time management

Consider a (unusual case of a) pipeline within a pipeline, going ASYNC to PLAYING (due to e.g. a live src).

Then the top-level pipeline will set up a base_time (to be distributed), however the contained pipeline will do the same, so we end up distributing that one's base_time to all elements.  When the pipeline has prerolled and is then finally going to PLAYING (all the way), the top-level will have it (original) base_time distributed again.

So, elements end up with conflicting/changing base_time (without intermittent state change), and afaik this should not happen (and is at least Not Nice).

Problem stems from the ASYNC_DONE state change handling explicitly checking for a top-level pipeline/bin, whereas the time (etc) manipulation in GstPipeline happens unconditionally.

Simple patch attached makes the latter also conditional (though not sure if it needs something more subtle there).