[gst-devel] GnlComposition Signals
Edward Hervey
bilboed at gmail.com
Tue Dec 14 22:04:44 CET 2010
On Tue, 2010-12-14 at 13:34 -0500, Timothy Braun wrote:
> Thank you Edward. That makes sense.
>
> I have a custom bin with ghosted pads in a gnlsource. I'm currently
> ghosting the pad upon creation and then adding the final internal link
> once decodebin2 tells me it's ready.
If you do that... gnloperation will think there's a static number of
sink pads.
gnloperation will dynamically request/release pads only if the element
it's controlling has a request sink pad template... meaning it'll work
with videomixer, but you'll have to do your own subclass of GstBin with
the proper pad templates to make it work (I'm assuming you want to put
some extra elements before videomixer).
> On occasion, I run into a data flow error, but not consistently.
> I'm thinking it may be related to the order in which I'm adding pads.
> Is it better to ghost the bins pad after decodebin is connected? or
> does this order not matter?
For sources it doesn't matter.
>
> Also, if I'm ghosting the pad, do I have to manually remove it once
> streaming of that source is complete? If so, what signal should I be
> listening for from gnlsource/gnlcomposition to know that its completed
> it's duties?
I'm assuming you mean for operations (doesn't matter for sources).
For operations with dynamic pads you want to make sure that:
* Your element (the one you put in gnloperation)
* Has a sink pad template of type GST_PAD_REQUEST
* you have overriden the GstElementClass::request_new_pad vmethod
In there you request a pad from videomixer, add your extra
elements, ghost the first element's sink pad, add that pad to yourself,
and return that pad
* you have overriden the GstElementClass::release_request_pad vmethod
In there you remove that pad from yourself, release the sink pad
you requested from videomixer, and remove all elements for that path
* You listen to the 'input-priority-changed' signal from gnloperation
This will notify you of changes in priority of incoming stream for
each of your ghost sink pad.
When you receive that, you change the 'associated' videomixer sinkpad
for that ghostpad of yours by setting the 'zorder' property of that
videomixer sinkpad to the priority you receive
g_object_set(thatstream->videomixersinkpad, "zorder", thenewpriority,
NULL);
This assumes you need to insert extra elements before/after your
videomixer in that operation (else you can just stick videomixer in a
gnloperation and all of that will be taken care of).
Hope this helps,
Edward
>
> Thanks again.
>
> Best,
> Tim
>
> On Tue, Dec 14, 2010 at 5:42 AM, Edward Hervey <bilboed at gmail.com>
> wrote:
>
> On Mon, 2010-12-13 at 17:33 -0500, Timothy Braun wrote:
> > Hey Everyone,
> > So I have a gnlcomposition which, for the matter of
> depicting the
> > situation, has 5 sources. 3 sources play for 30 seconds
> followed by
> > the remaining 2 sources for another 30 seconds. This should
> produce a
> > 1 minute video. The composition has a videomixer in a
> gnloperation to
> > mix the sources for final output.
> >
> > I'm running into a situation where the pipeline gets stuck
> during
> > the transition from 3 sources to 2 sources. It seems the
> video mixer
> > is trying to send a seek event to all it's sink pads, which
> fails on
> > the pad which no-longer has a source. During my tests, the
> > gnlcomposition will happily create new pads, ie. changing
> the order so
> > it's 2 sources followed by 3 sources works fine. But the
> opposite
> > doesn't seem to be true, the gnlcomposition doesn't remove
> unused pads
> > to it's operations.
> >
> > This brings me to the question of, is there a signal I'm
> not
> > handling appropriately? If so, any pointers on which one I
> should be
> > listening for?
>
>
> If the element you put in a gnloperation has dynamic sink
> pads, the
> gnloperation will call gst_element_request_pad() and
> gst_element_release_request_pad() when needed.
> videomixer alone should work fine in those cases. If you have
> put a
> custom element with ghostpads, make sure you check when they
> are
> added/removed and properly request/release the targets of
> those
> ghostpads.
>
> Edward
>
> >
> > Thanks,
> > Tim
> >
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