decodebin2

[Tim-Philipp Müller]

On Fri, 2012-03-09 at 09:34 +0100, Steffen.Roeber at hella.com wrote:

> I'm usng a pipeline that contains a filesrc, a decodebin, an appsink
> and some other elements. What I want to get is the duration of  the
> current element. 
> For this I'm using 
> GstQuery *frameDuration = gst_query_new_duration(GST_FORMAT_DEFAULT); 
> gst_element_query(reinterpret_cast<GstElement *>(m_pipeline),
> frameDuration); 
> sint64 temp = 0; 
> gst_query_parse_duration(frameDuration, 0, &temp); 
> 
> I have two problems with this approach. First, this works only after I
> called 
> GstBuffer *buffer = gst_app_sink_pull_buffer(m_appSink); 
> which is very annoying. 
> And the second problem is that it does not work at all if I change the
> filename of the filesrc: 
> gst_element_set_state(reinterpret_cast<GstElement *>(m_pipeline),
> GST_STATE_NULL); 
> setProperty(reinterpret_cast<GObject *>(aviSrc), "location",
> filename); 
> ... 

The duration should be available as soon as appsink (and all other
sinks) has queued a buffer internally and the pipeline is prerolled,
that is when you receive an ASYNC_DONE message on the bus (or a state
change message with new_state==PAUSED and message->src==pipeline).

There's no need to actually pull a buffer from appsink.

If you just want to read metadata, GstDiscoverer might also be of
interest.

As for changing filesrc - you should just set up a new filesrc +
decodebin2 (decodebin2 needs resetting as well) and remove the old
elements when no longer needed.

Cheers
 -Tim