Dynamically changing resolution of visualisations

Yogesh Marwaha yogeshm.007 at gmail.com
Sun Jul 24 08:56:40 PDT 2011

On Saturday 23 Jul 2011 20:14:17 Yogesh Marwaha wrote:
> Hi,
> I'm to add possibility of changing resolution of visualisation shown in my
> application (using playbin2; sparklemedia.sourceforge.net). Here are some
> points: -
I am now thinking of simplify things and allow there quality settings viz. 
Low, High, and Best.
Low: Visualisations are rendered in a size 1/4 of the widget's size
High: Visualisations are rendered in a size 1/2 of the widget's size
Best: Visualisations are rendered in a size 1/1 of the widget's size
> (I still have not coded anything regarding subject yet, only gst-launch
> stuff)
> * goom, for example, provides only one caps structure on its source pad, so
> changing its width and height is sufficient; but libvisual_jakdaw provides
> three caps structures on its source pad, which one should I use or should I
> change width/height on all?
I'm thinking of following bin as visualisation: -
goom (or any other visualisation) ! ffmpegcolorspace ! capsfilter ! videoscale

I've the following working (preliminary) code (please notice the caps, advice 
is needed on it): -
    GstElement *newVisualisationElement = 
gst_element_factory_make(visualisation.toLocal8Bit(), "visualisation1");
    GstElement *newCapsfilterElement = gst_element_factory_make("capsfilter", 
    GstCaps *caps = gst_caps_new_simple ("video/x-raw-yuv",
                                         "width", G_TYPE_INT, 640,
                                         "height", G_TYPE_INT, 480,
    g_object_set(G_OBJECT(newCapsfilterElement), "caps", caps, NULL);

    GstElement *newFfmpegcolorspaceElement = 
gst_element_factory_make("ffmpegcolorspace", "visualisation3");
    GstElement *newVideoscaleElement = gst_element_factory_make("videoscale", 
        m_pVisualisationBin = gst_bin_new("visualisation-bin");

newVisualisationElement, newFfmpegcolorspaceElement, newCapsfilterElement, 
newVideoscaleElement, NULL);
newFfmpegcolorspaceElement, newCapsfilterElement, newVideoscaleElement, NULL);
        gst_element_add_pad(m_pVisualisationBin, gst_ghost_pad_new("sink", 
gst_element_get_static_pad(newVisualisationElement, "sink")));
        gst_element_add_pad(m_pVisualisationBin, gst_ghost_pad_new("src", 
gst_element_get_static_pad(newVideoscaleElement, "src")));

        g_object_set(G_OBJECT(m_pPlayBin), "flags", PLAYBIN_FLAG_NO_VIS, 
        g_object_set(G_OBJECT(m_pPlayBin), "vis-plugin", m_pVisualisationBin, 
        g_object_set(G_OBJECT(m_pPlayBin), "flags", PLAYBIN_FLAG_VIS, NULL);
        mCurrentVisualisation = visualisation;
        return true;

Code is tested with xvimagesink and ximagesink with similar behaviour.
> * which element decides on what resolution the visualisation is run, and
> how? I suppose it to be visualisation element and some default values.
> * is there any way I can force the visualisation to render on same
> resolution as the current video output widget?



Yogesh Marwaha

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