Hello again!
2006/4/22, Артём Попов <artfwo gmail.com>:
> Hello,
>
> 21.04.06, Edward Hervey<bilboedgmail.com> написал(а):
> > Hi,
> >
> > On 4/21/06, Артём Попов <artfwogmail.com> wrote:
> > > Hi all,
> > >
> > > I'm trying to write a gst element in python,
based on
> > > GstBaseTransform. The core of such an element
would be "transform" and
> > > "transform_ip" methods, with
receive GstBuffer arguments. Both of
> > > these methods don't work for me, due to too
large reference count of
> > > Buffers passed to them. By the way, the
"transform" method requires
> > > "get_unit_size" virtual method to
be implemented, the patch is here:
> > >
> > > http
://bugzilla.gnome.org/show_bug.cgi?id=339248
> > >
> > > in "transform_ip", buffer
refcount is 3, and that makes the buffer unwritable
> > > in "transform", both buffer
refcounts are 2, what makes output buffer
> > > unwritable as well...
> > >
> > > def transform_ip (self, outbuf):
> > > print outbuf.__grefcount__ # always
prints 3
> > > return gst.FLOW_OK
> > >
> > > def transform (self, inbuf, outbuf):
> > > print inbuf.__grefcount__ # always prints
2
> > > print outbuf.__grefcount__ # always
prints 2
> > > return gst.FLOW_OK
> > >
> > > "gst_buffer_is_writable" checks,
that the buffer refcount should be 1,
> > > and gst-python uses just that to enable or
disable data writing to the
> > > buffer. So, how can I solve (or maybe
workaround) this problem?
> > > Thanks. --Artem
> >
> > Would it be possible to see your code ? Seeing
how you name your
> > methods, I doubt it'll work properly.
>
> Ah! Of course, they're "do_transform" and
"do_transform_ip", and so
> they are called in my code. It does nothing useful
except set_caps,
> get_unit_size and the transform test methods, that's
why I didn't post
> the complete class 
>
> >
> > Otherwise, we did refcount once too much, the
bug and patch are
> > available here (I can't commit right now since
cvs is frozen) :
> >
> > http
://bugzilla.gnome.org/show_bug.cgi?id=339308
> >
> > Please comment on the bug if it doesn't solve
your issues.
>
> Yeah, now the results are a bit different: here's what
I get (full
> code also posted in comment for bug #339308, also
posted here for
> convenience):
>
> def do_get_unit_size (self, caps):
> return 32 # buffer size (currently 2048) must be
divisible by this number
>
> def do_transform_ip (self, outbuf):
> print "ip:", outbuf.size,
outbuf.__grefcount__ # will print "2048 2"
> return gst.FLOW_OK
>
> def do_transform (self, inbuf, outbuf):
> print "noip:", inbuf.size,
inbuf.__grefcount__ # will print "2048 1"
> print "noip:", outbuf.size,
outbuf.__grefcount__ # will print "0 1"
> return gst.FLOW_OK
>
> So... do_transform_ip is still unusable, because
refcount is now
> smaller but still more than 1. The do_transform method
could actually
> work now if outbuf was not zero-sized. Right now
do_transform only
> prints values _once_ and the program is freezed (I
guess GStreamer is
> waiting for it to fill the output buffer or something
like that?)
>
> Well, the patch fixed the bug at least partially, but
it opens another
> issue: outbuf in do_transform is zeroed. What do you
think can be done
> to solve this?
Well, I've managed (by an absolutely weird workaround) to
make
outbuf.__grefcount__=1 in transform_ip:
I simply unref the buffer before calling python method and
then ref it
back again (otherwise I get a segfault). Here's what I've
added to the
proxy override:
gstbase.override:
...
%%
override GstBaseTransform__proxy_do_transform_ip
static GstFlowReturn
_wrap_GstBaseTransform__proxy_do_transform_ip(GstBaseTransfo
rm *self,
GstBuffer*buf)
{
...
gst_mini_object_unref ((GstMiniObject *) buf);
py_retval = PyObject_CallObject(py_method, py_args);
gst_mini_object_ref ((GstMiniObject *) buf);
...
}
I suppose, this completely weird and dirty way :( Could
there be a
cleaner solution for the above workaround?
--Artem
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