gstreamer/docs/random/ensonic/dynlink.txt
2019-10-06 11:12:11 -04:00

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$Id$
Currently its only save to link/unlink elements/pad when pipeline is in READY.
Belowe some thoughts. See http://bugzilla.gnome.org/show_bug.cgi?id=435487
for patches.
= current api =
gboolean gst_element_link (GstElement *src, GstElement *dest);
void gst_element_unlink (GstElement *src, GstElement *dest);
gst_element_link_many, gst_element_unlink_many, gst_element_link_filtered,
gst_element_link_pads, gst_element_unlink_pads, gst_element_link_pads_filtered
GstPadLinkReturn gst_pad_link (GstPad *srcpad, GstPad *sinkpad);
gboolean gst_pad_unlink (GstPad *srcpad, GstPad *sinkpad);
= use cases =
== inserting an element ==
* we have: e1 ! e4
* we want: e1 ! e2 ! e3 ! e4
* we want: e1 ! e2 ! e4
gst_element_insert_linked(e1, e2, e3, e4); // e2 == e3 allowed
gst_pads_insert_link (e1.src, e2.sink, e3.src, e4.sink);
disconnect e1.src, e1.src.peer
disconnect e4.sink, e4.sink.peer
connect e1.src, e2.sink
connect e3.src, e4.sink
== removing an element ==
* we have: e1 ! e2 ! e3
* we want: e1 ! e3
gst_element_remove_linked(e2);
gst_pads_remove_link (e1.src, e3.sink);
disconnect e1.src, e1.src.peer
disconnect e3.sink, e3.sink.peer
connect e1.src, e3.sink
== swapping out an elelment ==
* we have: e1 ! e2 ! e6
* we have: e1 ! e2 ! e3 ! e6
* we want: e1 ! e4 ! e5 ! e6
* we want: e1 ! e3 ! e6
gst_element_swap_linked(e1, e4, e5, e6);
gst_pads_insert_link (e1.src, e4.sink, e5.src, e6.sink);
disconnect e1.src, e1.src.peer (=e2.sink)
disconnect e6.sink, e6.sink.peer
connect e1.src, e4.sink
connect e5.src, e6.sink
= thoughts =
* I don't think we need api for pads
* Should current api check for the state?
* do we want to swapp multiple elements at once
== events ==
* tee and adder need special treatment
* both would need to cache an accumulated segment
* tee
* would also cache tags
* when linkfunc is called, it can send out the segment and the tags
* when all pads got unlinked it could clear the segment
* adder
* when linkfunc gets called it sends a seek-event
= ideas =
== dynlinkpoint ==
* use cases
* its meant to be used with one side disconnected to allow to connect elements
at runtime
* it can be used in a pipeline to remove/insert elements at runtime
* element with 1 source- and 1 sinkpad
* when both connected it passes data through
* if src is not connected it drops received buffers
* if sink is not connected
* it does not push
* it creates silence on pull
* events
* it caches events
* down: newsegment, tags, buffersize
* up: seek (needs to be modified)
* when other-pad get connected it pushes events depending on direction