docs/pwg/building-testapp.xml: Add some audioconverts and audioresample to the pipeline, and some more comments and e...

Original commit message from CVS:
* docs/pwg/building-testapp.xml:
Add some audioconverts and audioresample to the pipeline, and some
more comments and error handling.

ChangeLog

@@ -1,3 +1,9 @@
+2007-01-26  Tim-Philipp Müller  <tim at centricular dot net>
+
+	* docs/pwg/building-testapp.xml:
+	  Add some audioconverts and audioresample to the pipeline, and some
+	  more comments and error handling.
+
 2007-01-26  Tim-Philipp Müller  <tim at centricular dot net>
 
 	* docs/manual/manual.xml:

docs/pwg/building-testapp.xml

@@ -79,15 +79,19 @@ bus_call (GstBus     *bus,
       g_main_loop_quit (loop);
       break;
     case GST_MESSAGE_ERROR: {
-      gchar *debug;
-      GError *err;
+      gchar *debug = NULL;
+      GError *err = NULL;
 
       gst_message_parse_error (msg, &err, &debug);
-      g_free (debug);
 
       g_print ("Error: %s\n", err->message);
       g_error_free (err);
 
+      if (debug) {
+        g_print ("Debug deails: %s\n", debug);
+        g_free (debug);
+      }
+
       g_main_loop_quit (loop);
       break;
     }
@@ -102,8 +106,11 @@ gint
 main (gint   argc,
       gchar *argv[])
 {
+  GstStateChangeReturn ret;
   GstElement *pipeline, *filesrc, *decoder, *filter, *sink;
+  GstElement *convert1, *convert2, *resample;
   GMainLoop *loop;
+  GstBus *bus;
 
   /* initialization */
   gst_init (&argc, &argv);
@@ -115,37 +122,82 @@ main (gint   argc,
 
   /* create elements */
   pipeline = gst_pipeline_new ("my_pipeline");
-  gst_bus_add_watch (gst_pipeline_get_bus (GST_PIPELINE (pipeline)),
-		     bus_call, loop);
+
+  /* watch for messages on the pipeline's bus (note that this will only
+   * work like this when a GLib main loop is running) */
+  bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
+  gst_bus_add_watch (bus, bus_call, loop);
+  gst_object_unref (bus);
 
   filesrc  = gst_element_factory_make ("filesrc", "my_filesource");
   decoder  = gst_element_factory_make ("mad", "my_decoder");
+
+  /* putting an audioconvert element here to convert the output of the
+   * decoder into a format that my_filter can handle (we are assuming it
+   * will handle any sample rate here though) */
+  convert1 = gst_element_factory_make ("audioconvert", "audioconvert1");
+
+  /* use "identity" here for a filter that does nothing */
   filter   = gst_element_factory_make ("my_filter", "my_filter");
+
+  /* there should always be audioconvert and audioresample elements before
+   * the audio sink, since the capabilities of the audio sink usually vary
+   * depending on the environment (output used, sound card, driver etc.) */
+  convert2 = gst_element_factory_make ("audioconvert", "audioconvert2");
+  resample = gst_element_factory_make ("audioresample", "audioresample");
   sink     = gst_element_factory_make ("osssink", "audiosink");
+
   if (!sink || !decoder) {
     g_print ("Decoder or output could not be found - check your install\n");
     return -1;
+  } else if (!convert1 || !convert2 || !resample) {
+    g_print ("Could not create audioconvert or audioresample element, "
+             "check your installation\n");
+    return -1;
   } else if (!filter) {
     g_print ("Your self-written filter could not be found. Make sure it "
-             "is installed correctly in $(libdir)/gstreamer-0.9/ and that "
-             "you've ran gst-register-0.9 to register it. Check availability "
-             "of the plugin afterwards using \"gst-inspect-0.9 my_filter\"");
+             "is installed correctly in $(libdir)/gstreamer-0.10/ or "
+             "~/.gstreamer-0.10/plugins/ and that gst-inspect-0.10 lists it. "
+             "If it doesn't, check with 'GST_DEBUG=*:2 gst-inspect-0.10' for "
+             "the reason why it is not being loaded.");
     return -1;
   }
 
   g_object_set (G_OBJECT (filesrc), "location", argv[1], NULL);
 
+  gst_bin_add_many (GST_BIN (pipeline), filesrc, decoder, convert1, filter,
+                    convert2, resample, sink, NULL);
+
   /* link everything together */
-  gst_element_link_many (filesrc, decoder, filter, sink, NULL);
-  gst_bin_add_many (GST_BIN (pipeline), filesrc, decoder, filter, sink, NULL);
+  if (!gst_element_link_many (filesrc, decoder, convert1, filter, convert2,
+                              resample, sink, NULL)) {
+    g_print ("Failed to link one or more elements!\n");
+    return -1;
+  }
 
   /* run */
-  gst_element_set_state (pipeline, GST_STATE_PLAYING);
+  ret = gst_element_set_state (pipeline, GST_STATE_PLAYING);
+  if (ret == GST_STATE_CHANGE_FAILURE) {
+    g_print ("Failed to start up pipeline!\n");
+
+    /* check if there is an error message with details on the bus */
+    msg = gst_bus_poll (bus, GST_MESSAGE_ERROR, 0);
+    if (msg) {
+      GError *err = NULL;
+
+      gst_message_parse_error (msg, &err, NULL);
+      g_print ("ERROR: %s\n", err->message);
+      g_error_free (err);
+      gst_message_unref (msg);
+    }
+    return -1;
+  }
+
   g_main_loop_run (loop);
 
   /* clean up */
   gst_element_set_state (pipeline, GST_STATE_NULL);
-  gst_object_unref (GST_OBJECT (pipeline));
+  gst_object_unref (pipeline);
 
   return 0;
 }