gstreamer playbin2: no state change message from NULL to READY

[Tim-Philipp Müller]

On Thu, 2011-04-07 at 10:05 +0800, bcxa sz wrote:

> I just tried to use playbin2 play one avi file. And the file can be
> played well but from the application side, I can not receive element
> ffdec/avidemux state change message from NULL to READY. And I can
> receive element state change message from READY to PAUSED, and from
> PAUSED to PLAYING.
> 
> This is strange for other elements (like streamsynchronizer0,
> playsink0, uridecodebin0, typefind, decodebin20, multiqueue0,
> inputselector0, ...), I can receive stage change message from NULL to
> READY.
> 
> Anybody who help me to explain why? And I want to know how to modify
> playbin2 then I can get the demux and decoder state change from NULL
> to READY.

That's most likely because elements that are autoplugged based on
typefinding/caps discovery are set to READY state before being added to
decodebin2 (to see if they work).

Why do you need these particular state change messages? The application
only really needs to look at state change messages coming from the
top-level pipeline (ie. playbin2).

 Cheers
  -Tim