[gstreamer ]How to change the video resolution from gstplugin

Question

I am writing a gstreamer plugin to render the camera video(height=480, width=640 , format UYVY) on top of a HD video frame. In my chain function (gst_plugin_template_chain (GstPad * pad, GstObject * parent, GstBuffer * buf)) I can see the buf size as 480x640x2. I allocated a new buffer equivalent to Full HD and copied this UYVY data on top of the new buffer and replaced the existing buffer. But output video is still height=480, width=640.

Here are the code snippet.

gst_plugin_template_chain (GstPad * pad, GstObject * parent, GstBuffer * buf)
{
  GstPluginTemplate *filter;
  GstMapInfo map;
  guchar *data;
  gint width = 640, height = 480;
  GstMemory *mem;
  int row = 0;

  filter = GST_PLUGIN_TEMPLATE (parent);
  gst_buffer_map (buf, &map, GST_MAP_READWRITE);


  mem = gst_allocator_alloc(NULL, 4147200, NULL); //1080*1920*2 (Full HD UYVY) = 4147200
  GstMapInfo info_out;
  gst_memory_map(mem, &info_out, GST_MAP_WRITE);


 for(int i = 0; i < 480 ; i++) {
    memcpy(info_out.data + row, map.data + row, 1280);
    row += 1280; //640*2
  }

  gst_buffer_replace_all_memory(buf, mem);

  gst_buffer_unmap (buf, &map);
  gst_memory_unmap(mem, &info_out);

  return gst_pad_push (filter->srcpad, buf);
}
 

Answer 1

You need to send a new CAPS event downstream. Probably you want gst_event_new_caps() and push it through the source pad. But double check the documentation about what you want exactly.