[gst-devel] Bug in gst_bin_set_state ?

[Andreas Rottmann]

"Ronald S. Bultje" <rbultje at ronald.bitfreak.net> writes:

> Hi,
>
> On Thu, 2005-01-20 at 14:55, Andreas Rottmann wrote:
>> I tried to get v4l2src to work with gstreamer, and in the process
>> found out that gst_v4l2src_change_state was never called when setting
>> the state of the pipeline.
>
> That indicates a state-change failure (probably due to failing caps
> negotiation)... Did you check the return value? Dunno about the patch.
> ;). The else { .. } will call _change_state,
>
Will it? It seems that the GST_CALL_PARENT_WITH_DEFAULT expands into
GST_ELEMENT_CLASS(parent_class)->set_state (element, state); which
resolves to gst_element_set_state_func(element, state), which doesn't
seem to iterate the children.

> which will call gst_bin_change_state(), which will call
> gst_bin_foreach(set_kid_state_func) on all kids per state instead of
> one-for-all, which is the correct behaviour if you ask me.
>
Yeah, that what you describe seems correct behaviour, but it seems to
me that this is not what happens in the original code when the state
changes (i.e. GST_STATE (bin) != state).

> I'm not totally convinced that the if { .. } is needed at all, but
> your patch doesn't seem right if you look at it that way.
>
I still don't understand how

    return GST_CALL_PARENT_WITH_DEFAULT (GST_ELEMENT_CLASS, set_state, (element,
            state), GST_STATE_FAILURE);

is going to ever invoke the children's change_state functions, since
GstElement doesn't even know about children. An that is what is called
when you call gst_element_set_state (pipeline, GST_STATE_PLAYING) on a
pipeline that is *not* in GST_STATE_PLAYING (without my patch).

Rotty
-- 
Andreas Rottmann         | Rotty at ICQ      | 118634484 at ICQ | a.rottmann at gmx.at
http://yi.org/rotty      | GnuPG Key: http://yi.org/rotty/gpg.asc
Fingerprint              | DFB4 4EB4 78A4 5EEE 6219  F228 F92F CFC5 01FD 5B62

It's *GNU*/Linux dammit!