rookie question for writing a simple video player

[jaeyong yoo]

Hello,

I just read gstreamer application development manual (0.10.35.1) and want
to write a very simple video player.

I can play a video (mpeg2-encoded) using playbin in test/examples/manual
folder thus I tried to strip out the parts that handle the required
elements to play the particular video and wrote the code as follows.


#include <gst/gst.h>


static void handoff (GstElement * identity, GstBuffer * frame, gpointer
data)
{
    printf("handoff called\n");
}

static gboolean my_bus_callback (GstBus * bus, GstMessage * msg, gpointer
data)
{
    GMainLoop *loop = (GMainLoop *) data;

    switch (GST_MESSAGE_TYPE (msg)) {
        case GST_MESSAGE_EOS:
        {
            g_print ("End-of-stream\n");
            g_main_loop_quit (loop);
            printf("JYD: bus_call: GST_MESSAGE_EOS\n");
            break;
        }
        case GST_MESSAGE_ERROR:
        {
            gchar *debug;
            GError *err;
            printf("JYD: bus_call: GST_MESSAGE_ERROR\n");
            gst_message_parse_error (msg, &err, &debug);
            g_free (debug);
            g_print ("Error:: %s\n", err->message);
            g_error_free (err);
            g_main_loop_quit (loop);
            break;
        }
        case GST_MESSAGE_WARNING:
        {
            char buf[1024];
            sprintf( buf, "%s",  GST_MESSAGE_SRC_NAME(msg) );
            printf("JYD: bus_call: %s %s\n", GST_MESSAGE_TYPE_NAME(msg),
buf);

            break;
        }

        case GST_MESSAGE_STATE_CHANGED:
        {
            printf("JYD: bus_call: (%s: %d)\n", GST_MESSAGE_TYPE_NAME(msg),
GST_MESSAGE_TYPE(msg));
            /* TODO: how to see the changed element state? */
            break;
        }
        default:
            printf("JYD: bus_call: default (%s: %d)\n",
GST_MESSAGE_TYPE_NAME(msg), GST_MESSAGE_TYPE(msg));
            break;
    }
    return TRUE;
}

gint main (gint argc, gchar * argv[])
{
    GstElement *scale;
    GstElement *identity;
    GstElement *pipeline, *queue;
    GstElement *src, *dec, *conv, *sink;
    GMainLoop *loop;
    GstBus *bus;

    gst_init (&argc, &argv);

    if (argc < 2) {
        g_print ("usage: %s <media file or uri>\n", argv[0]);
        return 1;
    }

    /* create and event loop and feed gstreamer bus mesages to it */
    loop = g_main_loop_new (NULL, FALSE);

    /* create pipeline */
    pipeline = gst_pipeline_new ("pipeline");
    bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
    gst_bus_add_watch(bus, my_bus_callback, loop);
    gst_object_unref (bus);

    /* create an element for file-reading */
    src = gst_element_factory_make ("filesrc", "source");
    g_object_set (G_OBJECT (src), "location", argv[1], NULL);
    dec = gst_element_factory_make ("decodebin", "decode");
    queue = gst_element_factory_make ("queue", "preroll_video_src0" );
    sink = gst_element_factory_make ("autovideosink", "videosink");
    conv = gst_element_factory_make ("ffmpegcolorspace", "vconv");
    scale = gst_element_factory_make ("videoscale", "vscale");
    identity = gst_element_factory_make ("identity", "identity-for-what");
    g_object_set (identity, "silent", TRUE, NULL);
    g_signal_connect (identity, "handoff", G_CALLBACK (handoff), NULL);

    /* add elements to a bin */
    gst_bin_add_many( GST_BIN (pipeline), src, dec, queue, conv, scale,
identity, sink, NULL );

    /* link the elements in the bin */
    gst_element_link( src, dec );
    gst_element_link( dec, queue );
    gst_element_link( queue, identity );
    gst_element_link( identity, conv );
    gst_element_link( conv, scale );
    gst_element_link( scale, sink );


    /* start the bin */
    gst_element_set_state (pipeline, GST_STATE_PLAYING);

    /* start play back and listed to events */
    printf("go to main loop\n"); /* XXX you may start debugging here */
    g_main_loop_run (loop);
    printf("return from main loop\n");

    /* cleanup */
    g_object_unref (pipeline);
    g_object_unref (loop);

    return 0;
}


and the results give me the following

Error:: Internal data flow error.
return from main loop

(lt-myvideoplayer:26621): GStreamer-CRITICAL **:
Trying to dispose element videosink, but it is in PAUSED instead of the
NULL state.
You need to explicitly set elements to the NULL state before
dropping the final reference, to allow them to clean up.
This problem may also be caused by a refcounting bug in the
application or some element.


(lt-myvideoplayer:26621): GStreamer-CRITICAL **:
Trying to dispose element identity-for-what, but it is in PAUSED instead of
the NULL state.
You need to explicitly set elements to the NULL state before
dropping the final reference, to allow them to clean up.
This problem may also be caused by a refcounting bug in the
application or some element.


(lt-myvideoplayer:26621): GStreamer-CRITICAL **:
Trying to dispose element vscale, but it is in PAUSED instead of the NULL
state.
You need to explicitly set elements to the NULL state before
dropping the final reference, to allow them to clean up.
This problem may also be caused by a refcounting bug in the
application or some element.


(lt-myvideoplayer:26621): GStreamer-CRITICAL **:
Trying to dispose element vconv, but it is in PAUSED instead of the NULL
state.
You need to explicitly set elements to the NULL state before
dropping the final reference, to allow them to clean up.
This problem may also be caused by a refcounting bug in the
application or some element.


(lt-myvideoplayer:26621): GStreamer-CRITICAL **:
Trying to dispose element preroll_video_src0, but it is in PAUSED instead
of the NULL state.
You need to explicitly set elements to the NULL state before
dropping the final reference, to allow them to clean up.
This problem may also be caused by a refcounting bug in the
application or some element.


GThread-ERROR **: file
/build/buildd/glib2.0-2.30.0/./gthread/gthread-posix.c: line 171
(g_mutex_free_posix_impl): error 'Device or resource busy' during
'pthread_mutex_destroy ((pthread_mutex_t *) mutex)'
Trace/breakpoint trap


I'm stcuked in this phase.
Please help me.
Any comments, reading recommendations, would be very appreciated.

jaeyong
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