[gst-devel] Several novice questions
jeff_barish at earthlink.net
Fri Jan 18 17:14:03 CET 2008
Edward Hervey wrote:
> On Fri, 2008-01-18 at 08:28 -0700, Jeffrey Barish wrote:
>> 1. I gather that I am expected to change the state of the player on EOS
>> (which seems strange to me as I would have thought that the player would
>> know to stop playing when the stream has ended). To this end, I included
>> the following code:
>> self.player = gst.element_factory_make('playbin', 'player')
>> bus = self.player.get_bus()
>> bus.connect('message', self.on_message)
>> def on_message(self, bus, message):
>> print "Got message", message # nothing ever prints
>> t = message.type
>> if t in (gst.MESSAGE_EOS, gst.MESSAGE_ERROR):
>> However, on_message is never called. Any idea what I am doing wrong?
> Are you running a mainloop ? I think it won't work if you're not
> runnign a mainloop.
I have the impression that pygst takes care of the main loop for me. I
don't see main_loop in the pygst documentation nor in the tutorial
examples, nor does pygst have a function main_loop or mainloop.
>> 2. get_state() returns a tuple (with 3 elements) of the Element's current
>> state. Where is the documentation on the elements of the tuple? It
>> appears that the second element is the actual state. Is this observation
>> always true?
> Look in the C API for gst_element_get_state. The returned values are
> the 3 last arguments of that function.
I am getting a tuple with (type GstStateChangeReturn, type GstState, type
GstState), so I guess the first element is the return value of
gst_element_get_state, the second is the current state, and the third is
the pending state. I am interested in knowing more about how ASYNC state
changes work and when they are used.
>> 3. I would like to know the elapsed ratio so I tried
>> query_position(gst.FORMAT_PERCENT). I get a query error. It works to do
>> query_position(gst.FORMAT_TIME) and query_duration(gst.FORMAT_TIME) and
>> compute the ratio, but why doesn't the simpler solution work? Is
>> gst.FORMAT_PERCENT a percentage (0 to 100), as the name implies, or is it
>> actually a ratio (0 to 1)?
> What are you doing that query on ? the pipeline ? the sinks ?
I am doing the query on self.player:
ratio = self.player.query_position(gst.FORMAT_PERCENT)
position = self.player.query_position(gst.FORMAT_TIME)
Thanks for your quick reply.
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