Using "convert-sample" from playbin

[Chris Tapp]

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.

> Are you maybe leaking the target_caps?
> 
> -- 
> Sebastian Dröge, Centricular Ltd - http://www.centricular.com
> Expertise, Straight from the Source
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Chris Tapp

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www.keylevel.com