Reading "wav" file in "C"

aft aftnix at gmail.com
Wed Feb 5 03:46:25 PST 2014


Hi,

I'm trying to implement the following pipeline in 'C':

    arif at dev:~/GS_samples/cmd_GS$gst-launch-0.10 filesrc
location="../sample_media/M1F1-Alaw-AFsp.wav" ! wavparse ! alawdec !
autoaudiosink


Here is the implementation which i have written

    #include <gst/gst.h>

    void on_pad_added(GstElement *src_element, GstPad *src_pad, gpointer data);
    static gboolean bus_cb(GstBus *bus, GstMessage *message, gpointer data);

    static GMainLoop *loop;

    int main(int argc, char **argv) {

    GstElement *pipeline;
    GstElement *src;
    GstElement *dec;
    GstElement *parse;
    GstElement *sink;
    GstBus *bus;

    gst_init(&argc, &argv);

    loop = g_main_loop_new (NULL, FALSE);

    pipeline = gst_pipeline_new("wav_player");

    src = gst_element_factory_make("filesrc","src");
    sink = gst_element_factory_make("autoaudiosink","sink");
    parse = gst_element_factory_make("wavparse","parse");
    dec = gst_element_factory_make("alawdec", "dec");

    gst_bin_add_many (GST_BIN(pipeline), src,parse,dec,sink, NULL);
    g_object_set( G_OBJECT (src) , "location",argv[1], NULL);

    gst_element_link(src,parse);
    gst_element_link(dec,sink);
    g_signal_connect (dec, "pad-added", G_CALLBACK (on_pad_added), dec);

    bus = gst_pipeline_get_bus(GST_PIPELINE(pipeline));
    gst_bus_add_watch (bus, bus_cb, NULL);
    gst_object_unref(bus);
    gst_element_set_state(pipeline, GST_STATE_PLAYING);
    g_main_loop_run(loop);
    return 0;

    }

    void on_pad_added (GstElement *src_element, GstPad *src_pad, gpointer data)
    {
    g_print ("linking dynamic pad ...\n");

    GstElement *sink_element = (GstElement *) data;
    GstPad *sink_pad = gst_element_get_static_pad(sink_element, "sink");
    gst_pad_link (src_pad, sink_pad);
    gst_object_unref(sink_pad);

    }

    static gboolean bus_cb(GstBus *bus, GstMessage *message, gpointer    data)
    {
      g_print ("Got %s message\n", GST_MESSAGE_TYPE_NAME (message));

      switch (GST_MESSAGE_TYPE (message)) {
        case GST_MESSAGE_ERROR: {
          GError *err;
          gchar *debug;

          gst_message_parse_error (message, &err, &debug);
          g_print ("Error: %s\n", err->message);
          g_error_free (err);
          g_free (debug);

          g_main_loop_quit (loop);
          break;
        }
        case GST_MESSAGE_EOS:
          /* end-of-stream */
          g_main_loop_quit (loop);
          break;
        default:
          /* unhandled message */
          break;
      }

      /* we want to be notified again the next time there is a message
       * on the bus, so returning TRUE (FALSE means we want to stop watching
       * for messages on the bus and our callback should not be called again)
       */
      return TRUE;
    }


But this does not work :

    arif at dev:~/GS_samples/cmd_GS$./a.out ../sample_media/M1F1-Alaw-AFsp.wav
    Got state-changed message
    Got state-changed message
    Got stream-status message
    Got tag message
    Got error message
    Error: Internal data flow error.
-- 
-Cheers
-Arif


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