Gstreamer: How to set videomixer sink_0 caps in C
<p>What I want to do is simple. Enable the sink pads on video mixer:</p>

<pre><code>/* Manually link the mixer, which has "Request" pads */
mixer_sink_pad_template = gst_element_class_get_pad_template(GST_ELEMENT_GET_CLASS(videomixer), "sink_%u");
mixer_sink_pad = gst_element_request_pad(videomixer, mixer_sink_pad_template, NULL, NULL);
sink_pad = gst_element_get_static_pad(videomixer, "src");
gst_pad_link(sink_pad, mixer_sink_pad);   
</code></pre>

<p>And then set the alpha, xpos, ypos, e.g.</p>

<pre><code>g_object_set(videomixer, "sink_0::alpha", 0.5, NULL);
</code></pre>

<p>But, that does not work.</p>

<pre><code>(orig_code:22527): GLib-GObject-WARNING **: g_object_set_valist: object class 'GstVideoMixer2' has no property named 'sink_0::alpha'
</code></pre>

<p>I'm trying to figure out the syntax for getting the C code to set videomixer's sink_0 &amp; sink_1 pad properties.</p>

<p>Can someone point out how easy it is?</p>