Pipeline freeze at preroll on embedded system

[Sebastian Dröge]

On So, 2013-01-20 at 21:57 +0100, Julian Scheel wrote:

> > The GCond in question would usually be signalled when the state change
> > from PAUSED to PLAYING happens in basesink (or when
> > flushing/EOS/stepping). So what you could do is to check if
> > 
> > a) basesink is actually tried to be set from PAUSED to PLAYING (check if
> > the change_state function is called)
> 
> Actually I debugged this and the PAUSED to PLAYING transition is never happening. I can see that gstbasesrc change_state is called for GST_STATE_CHANGE_NULL_TO_READY as well as GST_STATE_CHANGE_READY_TO_PAUSED, but never for GST_STATE_CHANGE_PAUSED_TO_PLAYING.
> So now the question is why this would not happen?
> From where would that transition be initiated?

In "gst-launch-1.0 fakesrc ! fakesink" it would happen from the
application thread. See gstreamer/tools/gst-launch.c:1097

This happens after getting the STATE_CHANGED message for the state
change to PAUSED from the pipeline in "event_loop".

Backtrace would be something like:
> #0  gst_base_src_change_state (element=0x7b0110, 
>     transition=GST_STATE_CHANGE_PAUSED_TO_PLAYING) at gstbasesrc.c:3579
> #1  0x00007ffff7b335cc in gst_element_change_state (
>     element=element at entry=0x7b0110, transition=<optimized out>)
>     at gstelement.c:2594
> #2  0x00007ffff7b33fa1 in gst_element_set_state_func (element=0x7b0110, 
>     state=GST_STATE_PLAYING) at gstelement.c:2550
> #3  0x00007ffff7b1bd8c in gst_bin_element_set_state (next=GST_STATE_PLAYING, 
>     current=GST_STATE_PAUSED, start_time=0, base_time=1019601586303013, 
>     element=0x7b0110, bin=0x7b60f0) at gstbin.c:2308
> #4  gst_bin_change_state_func (element=0x7b60f0, 
>     transition=GST_STATE_CHANGE_PAUSED_TO_PLAYING) at gstbin.c:2610
> #5  0x00007ffff7b335cc in gst_element_change_state (
>     element=element at entry=0x7b60f0, transition=<optimized out>)
>     at gstelement.c:2594
> #6  0x00007ffff7b33fa1 in gst_element_set_state_func (element=0x7b60f0, 
>     state=GST_STATE_PLAYING) at gstelement.c:2550
> #7  0x000000000040395e in main (argc=4, argv=0x7fffffffe1d8)
>     at gst-launch.c:1097

> > and b) if and when the GCond is signalled (while waiting? before? is
> > something else waiting at that time, in which case changing from SIGNAL
> > to BROADCAST should help, etc).
> 
> As PAUSED_TO_PLAYING transition is not happening the GCond will not be signalled, right?

Yes, only when flushing/EOS otherwise.
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