gst_element_set_state failure and bus messages

[Nicolas Dufresne]

Few suggestion:

- Use the latest stable from the 1.2 series
- Make sure you check the state change source object (state change is
reported for each elements independently). 
- Make sure you do your cleanup when you receive an error message. The
state after an error is undefined. You must set your pipeline state to
NULL in order to recover.

Le mardi 29 juillet 2014 à 11:50 +0200, Carlos Rafael Giani a écrit :
> Hello,
> 
> I saw something strange the other day with state changes with GStreamer 
> 1.2.0. During a test, I intentionally used filesrc with an invalid 
> filename. As expected, the state change from READY to PAUSED failed. As 
> part of the cleanup operation that followed, I called 
> gst_element_set_state() again, this time setting the pipeline to the 
> NULL state. This returned GST_STATE_CHANGE_SUCCESS , so the state change 
> finished immediately. Perhaps the pipeline is automatically set to NULL 
> if a state change fails?
> 
> Either way, I also noticed that the bus watch did not get any kind of 
> message that the state was changed to NULL. This caused problems, 
> because some final cleanup operations rely on seeing a state change to 
> NULL in the bus watch.
> 
> Is this some kind of exception? If state change fails, it is implicitely 
> set to NULL, and no state change messages will occur? Or perhaps this is 
> just a bug? I will test with a newer GStreamer version today.
> Also, if a state change finishes immediately (that is, returns 
> GST_STATE_CHANGE_SUCCESS instead of GST_STATE_CHANGE_ASYNC), will it 
> still produce bus watch statechange messages?
> 
> cheers
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