Framegrabber Fetching Issue

[Tejas Ravichandran]

Hello Everyone,


I am using a framegrabber to capture frames from multiple v4l2 source
cameras. So here is how i am doing it...

1) Creating a framesource reference pointer for every source depending on
the number of sources.

2) Once the framesource reference pointer is created ,a constructor is
called which initializes the Gstreamer Pipeline for every source
    starts playing it.

   Here is the pipeline ...

   v4l2src device  -> videoconvert -> appsink.

3) And then the fetch() function is used to pull the buffer from the
appsink and use the buffer for further processing.

However I am  facing a problem here.


This application works perfectly for the following configurations of
v4l2src caps and app-sink caps respectively.
  v4l2srccaps appsink-caps
1) YUY2     RGB

2) RGB       YUY2

3) RGB      RGBA

However for the following configurations, it captures properly for the
first time in all the devices but fails to capture for the second time...
no error messages though ....it just keeps waiting

    v4l2src-caps appsink-caps

1) YUY2 YUY2

2) RGB RGB

Any help would be appreciated :)

The following is the code for the pipeline initialization.

bool GStreamerCameraFrameSourceImpl::InitializeGstPipeLine()
{
    GstStateChangeReturn status;
    end = true;

    pipeline = GST_PIPELINE(gst_pipeline_new(NULL));
    if (pipeline == NULL)
    {
        NVXIO_PRINT("Cannot create Gstreamer pipeline");
        return false;
    }

    bus = gst_pipeline_get_bus(GST_PIPELINE (pipeline));

    // create v4l2src
    GstElement * v4l2src = gst_element_factory_make("v4l2src", NULL);
    if (v4l2src == NULL)
    {
        NVXIO_PRINT("Cannot create v4l2src");
        FinalizeGstPipeLine();

        return false;
    }

    std::ostringstream cameraDev;
    cameraDev << "/dev/video" << cameraIdx;
    g_object_set(G_OBJECT(v4l2src), "device", cameraDev.str().c_str(),
NULL);

    gst_bin_add(GST_BIN(pipeline), v4l2src);

    // create color convert element
    GstElement * color = gst_element_factory_make(COLOR_ELEM, NULL);
    if (color == NULL)
    {
        NVXIO_PRINT("Cannot create %s element", COLOR_ELEM);
        FinalizeGstPipeLine();

        return false;
    }

    gst_bin_add(GST_BIN(pipeline), color);

    /*GstElement * scale = gst_element_factory_make("videoscale", NULL);
    if (scale == NULL)
    {
        NVXIO_PRINT("Cannot create videoscale element");
        FinalizeGstPipeLine();

        return false;
    }

    gst_bin_add(GST_BIN(pipeline), scale);
*/

    // create appsink element
    sink = gst_element_factory_make("appsink", NULL);
    if (sink == NULL)
    {
        NVXIO_PRINT("Cannot create appsink element");
        FinalizeGstPipeLine();

        return false;
    }

    gst_bin_add(GST_BIN(pipeline), sink);

    // if initial values for FrameSource::Parameters are not
    // specified, let's set them manually to prevent very huge images
    if (configuration.frameWidth == (vx_uint32)-1)
        configuration.frameWidth = 1920;
    if (configuration.frameHeight == (vx_uint32)-1)
        configuration.frameHeight = 1080;
    if (configuration.fps == (vx_uint32)-1)
        configuration.fps = 30;

#if GST_VERSION_MAJOR == 0
    std::unique_ptr<GstCaps, GStreamerObjectDeleter> caps_v42lsrc(
        gst_caps_new_simple ("video/x-raw-rgb",
                             "width", GST_TYPE_INT_RANGE, 1,
(int)configuration.frameWidth,
                             "height", GST_TYPE_INT_RANGE, 1,
(int)configuration.frameHeight,
                             "framerate", GST_TYPE_FRACTION,
(int)configuration.fps,
                             NULL));
#else
    std::ostringstream stream;
    /*stream << "video/x-raw, format=(string){RGB, GRAY8}, width=[1," <<
configuration.frameWidth <<
              "], height=[1," << configuration.frameHeight << "],
framerate=" << configuration.fps << "/1;";*/
    stream << "video/x-raw, format=(string)RGB, width=" <<
configuration.frameWidth <<
              ", height=" << configuration.frameHeight << ";";

    std::unique_ptr<GstCaps, GStreamerObjectDeleter>
caps_v42lsrc(gst_caps_from_string(stream.str().c_str()));
#endif

    if (!caps_v42lsrc)
    {
        NVXIO_PRINT("Failed to create caps");
        FinalizeGstPipeLine();

        return false;
    }

    // link elements
    if (!gst_element_link_filtered(v4l2src, color, caps_v42lsrc.get()))
    {
        NVXIO_PRINT("GStreamer: cannot link v4l2src -> color using caps");
        FinalizeGstPipeLine();

        return false;
    }

    // link elements
    /*if (!gst_element_link(color, scale))
    {
        NVXIO_PRINT("GStreamer: cannot link color -> scale");
        FinalizeGstPipeLine();
        std::cout << "Cannot link color and scale\n";

        return false;
    }*/

    if (!gst_element_link(color, sink))
    {
        NVXIO_PRINT("GStreamer: cannot link color -> appsink");
        FinalizeGstPipeLine();

        return false;
    }

    gst_app_sink_set_max_buffers (GST_APP_SINK(sink), 1);
    gst_app_sink_set_drop (GST_APP_SINK(sink), true);

    // do not emit signals: all calls will be synchronous and blocking
    gst_app_sink_set_emit_signals (GST_APP_SINK(sink), 0);

#if GST_VERSION_MAJOR == 0
    std::unique_ptr<GstCaps, GStreamerObjectDeleter> caps_appsink(
            gst_caps_new_simple("video/x-raw-rgb",
                                "bpp",        G_TYPE_INT, 24,
                                "red_mask",   G_TYPE_INT, 0xFF0000,
                                "green_mask", G_TYPE_INT, 0x00FF00,
                                "blue_mask",  G_TYPE_INT, 0x0000FF,
                                NULL));
#else
    // support 1 and 4 channel 8 bit data
    std::unique_ptr<GstCaps, GStreamerObjectDeleter> caps_appsink(
            gst_caps_from_string("video/x-raw, format=(string){RGBA,
GRAY8};"));
#endif
    gst_app_sink_set_caps(GST_APP_SINK(sink), caps_appsink.get());

    // Force pipeline to play video as fast as possible, ignoring system
clock
    gst_pipeline_use_clock(pipeline, NULL);

    status = gst_element_set_state(GST_ELEMENT(pipeline),
GST_STATE_PLAYING);
    handleGStreamerMessages();

    if (status == GST_STATE_CHANGE_ASYNC)
    {
        // wait for status update
        status = gst_element_get_state(GST_ELEMENT(pipeline), NULL, NULL,
GST_CLOCK_TIME_NONE);
    }

    if (status == GST_STATE_CHANGE_FAILURE)
    {
        NVXIO_PRINT("GStreamer: unable to start playback");
        FinalizeGstPipeLine();

        std::cout << "Cannot initialize Gstreamer pipeline because of
STATE_CHANGE_FAILURE" << std::endl;

        return false;
    }

    // explicitly set params to -1 to ensure
    // their update in the updateConfiguration() function
    configuration.frameWidth = (vx_uint32)-1;
    configuration.frameHeight = (vx_uint32)-1;

    if (!updateConfiguration(color, configuration))
    {
        FinalizeGstPipeLine();
        return false;
    }

    end = false;

    return true;
}

}
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