Flow of PAUSE request from gstreamer to upper QT application.

[Sebastian Dröge]

On Mo, 2013-12-02 at 02:36 -0800, sathish wrote:
> Thanks Sebastian for the reply,
> 
> I will raise the issue with phonon developers..
> 
> I have a few questions/doubts regarding your reply..
> 
> "However when shortly looking at the code I don't see it handling the
> request-state message at all. This would need to be implemented. As
> Phonon is a very high-level abstraction of a media playback API, I would
> expect it to handle that internally without the application having to
> worry about that"
> 
> From the above statement, do you mean that GSTREAMER is processing the
> request and sending it PHONON but PHONON is not handling it ??..
>
> Or do you mean that PHONON should take full responsibilty and handle it. I
> see this scenario less because when I used gst launch instead of QT, I was
> able to CORK/PAUSE a player..

Both. Phonon does not handle it, but should handle it in a way that the
Qt application does not need to know about it at all.

> My second question is this..
> 
> The lines of interest are pasted below
> 
> >     gst_element_post_message (GST_ELEMENT_CAST (psink),
> >         gst_message_new_request_state (GST_OBJECT_CAST (psink),
> >             GST_STATE_PAUSED));
> 
> I went through the gstreamer documetation to find what does
> "gst_message_new_request_state ()" do ??
> 
> I got this reply.. "This message can be posted by elements when they want
> to have their state changed. A typical use case would be an audio server
> that wants to pause the pipeline because a higher priority stream is being
> played."
> 
> But what does it exactly post on the bus.. Does it post the state
> "GST_STATE_PAUSED" on the bus that needs handling ??

It posts a GstMessage on the bus, and the application (or Phonon or
whatever created the pipeline) gets that message from the bus. Then this
code is responsible for setting the pipeline to this requested state.

-- 
Sebastian Dröge <sebastian at centricular.com>
Centricular Ltd - http://www.centricular.com
Expertise, Straight from the Source
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