Update

subprojects/gst-docs/examples/tutorials/xcode iOS/Tutorial 2/GStreamerBackend.m

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+#import "GStreamerBackend.h"
+
+#include <gst/gst.h>
+
+GST_DEBUG_CATEGORY_STATIC (debug_category);
+#define GST_CAT_DEFAULT debug_category
+
+@interface GStreamerBackend()
+-(void)setUIMessage:(gchar*) message;
+-(void)app_function;
+-(void)check_initialization_complete;
+@end
+
+@implementation GStreamerBackend {
+    id ui_delegate;        /* Class that we use to interact with the user interface */
+    GstElement *pipeline;  /* The running pipeline */
+    GMainContext *context; /* GLib context used to run the main loop */
+    GMainLoop *main_loop;  /* GLib main loop */
+    gboolean initialized;  /* To avoid informing the UI multiple times about the initialization */
+}
+
+/*
+ * Interface methods
+ */
+
+-(id) init:(id) uiDelegate
+{
+    if (self = [super init])
+    {
+        self->ui_delegate = uiDelegate;
+
+        GST_DEBUG_CATEGORY_INIT (debug_category, "tutorial-2", 0, "iOS tutorial 2");
+        gst_debug_set_threshold_for_name("tutorial-2", GST_LEVEL_DEBUG);
+
+        /* Start the bus monitoring task */
+        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+            [self app_function];
+        });
+    }
+
+    return self;
+}
+
+-(void) dealloc
+{
+    if (pipeline) {
+        GST_DEBUG("Setting the pipeline to NULL");
+        gst_element_set_state(pipeline, GST_STATE_NULL);
+        gst_object_unref(pipeline);
+        pipeline = NULL;
+    }
+}
+
+-(void) play
+{
+    if(gst_element_set_state(pipeline, GST_STATE_PLAYING) == GST_STATE_CHANGE_FAILURE) {
+        [self setUIMessage:"Failed to set pipeline to playing"];
+    }
+}
+
+-(void) pause
+{
+    if(gst_element_set_state(pipeline, GST_STATE_PAUSED) == GST_STATE_CHANGE_FAILURE) {
+        [self setUIMessage:"Failed to set pipeline to paused"];
+    }
+}
+
+/*
+ * Private methods
+ */
+
+/* Change the message on the UI through the UI delegate */
+-(void)setUIMessage:(gchar*) message
+{
+    NSString *string = [NSString stringWithUTF8String:message];
+    if(ui_delegate && [ui_delegate respondsToSelector:@selector(gstreamerSetUIMessage:)])
+    {
+        [ui_delegate gstreamerSetUIMessage:string];
+    }
+}
+
+/* Retrieve errors from the bus and show them on the UI */
+static void error_cb (GstBus *bus, GstMessage *msg, GStreamerBackend *self)
+{
+    GError *err;
+    gchar *debug_info;
+    gchar *message_string;
+
+    gst_message_parse_error (msg, &err, &debug_info);
+    message_string = g_strdup_printf ("Error received from element %s: %s", GST_OBJECT_NAME (msg->src), err->message);
+    g_clear_error (&err);
+    g_free (debug_info);
+    [self setUIMessage:message_string];
+    g_free (message_string);
+    gst_element_set_state (self->pipeline, GST_STATE_NULL);
+}
+
+/* Notify UI about pipeline state changes */
+static void state_changed_cb (GstBus *bus, GstMessage *msg, GStreamerBackend *self)
+{
+    GstState old_state, new_state, pending_state;
+    gst_message_parse_state_changed (msg, &old_state, &new_state, &pending_state);
+    /* Only pay attention to messages coming from the pipeline, not its children */
+    if (GST_MESSAGE_SRC (msg) == GST_OBJECT (self->pipeline)) {
+        gchar *message = g_strdup_printf("State changed to %s", gst_element_state_get_name(new_state));
+        [self setUIMessage:message];
+        g_free (message);
+    }
+}
+
+/* Check if all conditions are met to report GStreamer as initialized.
+ * These conditions will change depending on the application */
+-(void) check_initialization_complete
+{
+    if (!initialized && main_loop) {
+        GST_DEBUG ("Initialization complete, notifying application.");
+        if (ui_delegate && [ui_delegate respondsToSelector:@selector(gstreamerInitialized)])
+        {
+            [ui_delegate gstreamerInitialized];
+        }
+        initialized = TRUE;
+    }
+}
+
+/* Main method for the bus monitoring code */
+-(void) app_function
+{
+    GstBus *bus;
+    GSource *bus_source;
+    GError *error = NULL;
+
+    GST_DEBUG ("Creating pipeline");
+
+    /* Create our own GLib Main Context and make it the default one */
+    context = g_main_context_new ();
+    g_main_context_push_thread_default(context);
+
+    /* Build pipeline */
+    pipeline = gst_parse_launch("audiotestsrc ! audioconvert ! audioresample ! autoaudiosink", &error);
+    if (error) {
+        gchar *message = g_strdup_printf("Unable to build pipeline: %s", error->message);
+        g_clear_error (&error);
+        [self setUIMessage:message];
+        g_free (message);
+        return;
+    }
+
+    /* Instruct the bus to emit signals for each received message, and connect to the interesting signals */
+    bus = gst_element_get_bus (pipeline);
+    bus_source = gst_bus_create_watch (bus);
+    g_source_set_callback (bus_source, (GSourceFunc) gst_bus_async_signal_func, NULL, NULL);
+    g_source_attach (bus_source, context);
+    g_source_unref (bus_source);
+    g_signal_connect (G_OBJECT (bus), "message::error", (GCallback)error_cb, (__bridge void *)self);
+    g_signal_connect (G_OBJECT (bus), "message::state-changed", (GCallback)state_changed_cb, (__bridge void *)self);
+    gst_object_unref (bus);
+
+    /* Create a GLib Main Loop and set it to run */
+    GST_DEBUG ("Entering main loop...");
+    main_loop = g_main_loop_new (context, FALSE);
+    [self check_initialization_complete];
+    g_main_loop_run (main_loop);
+    GST_DEBUG ("Exited main loop");
+    g_main_loop_unref (main_loop);
+    main_loop = NULL;
+
+    /* Free resources */
+    g_main_context_pop_thread_default(context);
+    g_main_context_unref (context);
+    gst_element_set_state (pipeline, GST_STATE_NULL);
+    gst_object_unref (pipeline);
+
+    return;
+}
+
+@end