Meego camera input

[Stefan Kost]

On 09/05/11 10:45, Peter Staab wrote:
> Hello,
>
> I am trying to record video with gstreamer on a N950 Meego device (from a Qt application). For first tests I adopted this sample code: http://maemo.org/maemo_release_documentation/maemo4.1.x/node9.html

you don't wan to send rgb to xvimagesink. I'd also suggest to use
autovideosink.

Stefan
> The adopted code looks this way:
> #####
> /* Initialize Gstreamer */
>     gst_init(NULL, NULL);
>
>     /* Create pipeline and attach a callback to it's
>      * message bus */
>     pipeline = gst_pipeline_new("test-camera");
>
>     bus = gst_pipeline_get_bus(GST_PIPELINE(pipeline));
>     gst_bus_add_watch(bus, (GstBusFunc)bus_callback, this);
>     gst_object_unref(GST_OBJECT(bus));
>
>     /* Create elements */
>     /* Camera video stream comes from a Video4Linux driver */
>     camera_src = gst_element_factory_make("autovideosrc", "camera_src"); //also tested: subdevsrc, v4l2camsrc, v4l2src
>     /* Colorspace filter is needed to make sure that sinks understands
>      * the stream coming from the camera */
>     csp_filter = gst_element_factory_make("ffmpegcolorspace", "capsfilter");
>     /* Tee that copies the stream to multiple outputs */
>     tee = gst_element_factory_make("tee", "tee");
>     /* Queue creates new thread for the stream */
>     screen_queue = gst_element_factory_make("queue", "screen_queue");
>     /* Sink that shows the image on screen. Xephyr doesn't support XVideo
>      * extension, so it needs to use ximagesink, but the device uses
>      * xvimagesink */
>     screen_sink = gst_element_factory_make("xvimagesink", "screen_sink");
>     /* Creates separate thread for the stream from which the image
>      * is captured */
>     image_queue = gst_element_factory_make("queue", "image_queue");
>     /* Filter to convert stream to use format that the gdkpixbuf library
>      * can use */
>     image_filter = gst_element_factory_make("ffmpegcolorspace", "image_filter");
>     /* A dummy sink for the image stream. Goes to bitheaven */
>     image_sink = gst_element_factory_make("fakesink", "image_sink");
>
>     /* Check that elements are correctly initialized */
>     if(!(pipeline && camera_src && screen_sink && csp_filter && screen_queue
>             && image_queue && image_filter && image_sink))
>     {
>             qDebug() << "Couldn't create pipeline elements";
>             QApplication::exit(0);
>     }
>
>     /* Set image sink to emit handoff-signal before throwing away
>      * it's buffer */
>     g_object_set(G_OBJECT(image_sink),
>                     "signal-handoffs", TRUE, NULL);
>
>
>
>     /* Add elements to the pipeline. This has to be done prior to
>      * linking them */
>     gst_bin_add_many(GST_BIN(pipeline), camera_src, csp_filter,
>                     tee, screen_queue, screen_sink, image_queue,
>                     image_filter, image_sink, NULL);
>
>     /* Specify what kind of video is wanted from the camera */
>     caps = gst_caps_new_simple("video/x-raw-rgb", //x-raw-rgb yuv
>                     "width", G_TYPE_INT, 640,
>                     "height", G_TYPE_INT, 480,
>                     NULL);
>
>     if (!caps)
>     {
>         qDebug() << "caps NULL";
>     }
>
>
>     /* Link the camera source and colorspace filter using capabilities
>      * specified */
>     if(!gst_element_link_filtered(camera_src, csp_filter, caps))
>     {
>         qDebug() << "gst_element_link_filtered caps error";
>      //   QApplication::exit(0);
>     }
>     gst_caps_unref(caps);
>
>     /* Connect Colorspace Filter -> Tee -> Screen Queue -> Screen Sink
>      * This finalizes the initialization of the screen-part of the pipeline */
>     if(!gst_element_link_many(csp_filter, tee, screen_queue, screen_sink, NULL))
>     {
>         qDebug() << "gst_element_link_many tee error";
>         QApplication::exit(0);
>     }
>
>     /* gdkpixbuf requires 8 bits per sample which is 24 bits per
>      * pixel */
>     caps = gst_caps_new_simple("video/x-raw-rgb",
>                     "width", G_TYPE_INT, 640,
>                     "height", G_TYPE_INT, 480,
>                     "bpp", G_TYPE_INT, 24,
>                     "depth", G_TYPE_INT, 24,
>                     "framerate", GST_TYPE_FRACTION, 15, 1,
>                     NULL);
>
>     /* Link the image-branch of the pipeline. The pipeline is
>      * ready after this */
>     if(!gst_element_link_many(tee, image_queue, image_filter, NULL))
>     {
>         qDebug() << "gst_element_link_many image_queue error";
>         QApplication::exit(0);
>     }
>
>     if(!gst_element_link_filtered(image_filter, image_sink, caps))
>     {
>         qDebug() << "gst_element_link_filtered image_sink error";
>         QApplication::exit(0);
>     }
>
>     gst_caps_unref(caps);
>
>     /* As soon as screen is exposed, window ID will be advised to the sink */
>     //g_signal_connect(this, "expose-event", G_CALLBACK(expose_cb),
>     //                 screen_sink);
>
>     GstStateChangeReturn sret = gst_element_set_state(pipeline, GST_STATE_PLAYING);
>     if(sret == GST_STATE_CHANGE_FAILURE)
>     {
>         qDebug() << "Error GST_STATE_PLAYING: " << sret;
>     }
>     else
>     {
>         qDebug() << "Ok GST_STATE_PLAYING: " << sret;
>     }
> #####
>
> Now the problem is that I just get "GST_STATE_CHANGE_FAILURE" as result and no preview (no error/debug messages).
> I already tested different parameters and looked into the Qt Mobility source code for reference which uses gstreamer too, all without success.
>
> Is there something wrong with the code, or can someone provide me a simple working example how to make the camera preview visible (in Qt/Meego)?
>
> Regards,
> Peter