Using "convert-sample" from playbin

[Sebastian Dröge]

On So, 2014-08-03 at 20:12 +0100, Chris Tapp wrote:
> On 3 Aug 2014, at 08:37, Sebastian Dröge <sebastian at centricular.com> wrote:
> 
> > On So, 2014-08-03 at 01:45 +0100, Chris Tapp wrote:
> >> I want to be able to grab a converted copy of the most recent frame from a video pipeline.
> >> 
> >> The pipeline is created using gst_parse_launch() and contains a "playbin" element.
> > 
> > You can also just use pipeline = gst_element_factory_make("playbin", NULL);
> > 
> >> I then use the following to grab and process the converted frames:
> >> 
> >>  g_signal_emit_by_name( pipeline, "convert-sample", target_caps, &frame );
> >> 
> >>  // Process frame...
> >> 
> >>  gst_sample_unref( frame );
> >> 
> >> However, this causes a memory leak. What am I doing wrong?
> > 
> > Impossible to say without more code. Can you provide a testcase that
> > reproduces it?
> 
> I've actually reduced the code to just a little bit more than above and still see the problem:
> 
>  GstCaps * caps;
> 
>  caps = gst_caps_new_simple( ... );
> 
>  g_signal_emit_by_name( pipeline, "convert-sample", target_caps, &frame );
> 
>  // Process frame...
> 
>  gst_sample_unref( frame );
> 
>  gst_caps_unref( caps );
> 
> After a bit of digging I noticed that GST_OBJECT_REFCOUNT_VALUE( frame ) reports a ref count of 2, but I would have expected a value of 1.
> 
> Adding a second gst_sample_unref( frame ) call fixes the problem.

That's not a fix though :)

What are you doing between g_signal_emit_by_name() and
gst_sample_unref()? Are you leaking a reference of anything from the
sample there?

-- 
Sebastian Dröge, Centricular Ltd - http://www.centricular.com
Expertise, Straight from the Source
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