Please, give an example of an action signal usage.

[wl2776]

Documentation says, that I can freely emit such signals on live instances without need of extra pre- and post processing. "They can also be thought of as object methods which can be called generically by third-party code."

I am reading in the playbin2 documentation :

The "get-audio-tags" signal

GstTagList* user_function (GstPlayBin2 *playbin,
                                        gint         stream,
                                        gpointer     user_data)      : Run Last / Action

How do I use this in my code?

I usually define a callback function - the signal handler - and call g_signal_connect(m_playbin, "signal_name","details", etc )
And, after this, when the signal emitted, my function is called.

But, in case of the "get-audio-tags" signal, where the returned GstTagList * will go?
And where should I put its processing?

[Stefan Sauer]

Am 01.04.2010 18:11, schrieb wl2776:

>
> Documentation says, that I can freely emit such signals on live instances
> without need of extra pre- and post processing. "They can also be thought of
> as object methods which can be called generically by third-party code."
>
> I am reading in the playbin2 documentation :
>
> The "get-audio-tags" signal
>
> GstTagList* user_function (GstPlayBin2 *playbin,
>                                         gint         stream,
>                                         gpointer     user_data)      : Run
> Last / Action
>
> How do I use this in my code?
>
> I usually define a callback function - the signal handler - and call
> g_signal_connect(m_playbin, "signal_name","details", etc )
> And, after this, when the signal emitted, my function is called.
>
> But, in case of the "get-audio-tags" signal, where the returned GstTagList *
> will go?
> And where should I put its processing?
>

from the glib docs (please check those first in the future, you need to
understand the underlying technologies, we can help with gstreamer specific
things, which this is not).

----------------------------------------------------------------------------
G_SIGNAL_ACTION

Action signals are signals that may freely be emitted on alive objects from user
code via g_signal_emit() and friends, without the need of being embedded into
extra code that performs pre or post emission adjustments on the object. They
can also be thought of as object methods which can be called generically by
third-party code.
----------------------------------------------------------------------------

You can look e.g. at camerabin example code to see how it is used.

Stefan

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[wl2776]

Stefan Kost wrote

from the glib docs (please check those first in the future, you need to
understand the underlying technologies, we can help with gstreamer specific
things, which this is not).
 [skip ]

You can look e.g. at camerabin example code to see how it is used.

Thank you. I've read this already, and cited in my original message.
I will be happy to understand the underlying technologies as quickly as possible, but, unfortunately, my information sources are poor. All action signals of the camerabin have void return type and don't return any values.

The docs to the g_signal_emit () function say that its "..." parameter is the list of "parameters to be passed to the signal, followed by a location for the return value. If the return type of the signal is G_TYPE_NONE, the return value location can be omitted."

Does it mean that I should call, for example,
  GstTagList *taglist;
  g_signal_emit_by_name(m_player, "get-audio-tags", &taglist);

?

[Stefan Sauer]

Am 02.04.2010 11:42, schrieb wl2776:

>
>
> Stefan Kost wrote:
>>
>> from the glib docs (please check those first in the future, you need to
>> understand the underlying technologies, we can help with gstreamer
>> specific
>> things, which this is not).
>>  [skip ]
>>
>> You can look e.g. at camerabin example code to see how it is used.
>>
>
> Thank you. I've read this already, and cited in my original message.
> I will be happy to understand the underlying technologies as quickly as
> possible, but, unfortunately, my information sources are poor. All action
> signals of the camerabin have void return type and don't return any values.
>
> The docs to the g_signal_emit () function say that its "..." parameter is
> the list of "parameters to be passed to the signal, followed by a location
> for the return value. If the return type of the signal is G_TYPE_NONE, the
> return value location can be omitted."
>
> Does it mean that I should call, for example,
>   GstTagList *taglist;
>   g_signal_emit_by_name(m_player, "get-audio-tags", &taglist);
>
> ?

I think it is
g_signal_emit_by_name(m_player, "get-audio-tags", stream_nr, &taglist);

Stefan

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