ocarina/gui/gst.cpp

/*
 * Copyright 2014 (c) Anna Schumaker.
 */
#include <core/audio.h>
#include <core/driver.h>
#include <gst/gst.h>

class GSTDriver;

static GSTDriver *gst_driver;


/**
 * Driver for the GStreamer audio library.
 *
 * The shell command `gst-inspect-1.0 --help-gst` details the command line
 * options that can be passed to Ocarina.
 */
class GSTDriver : public Driver
{
private:
	GstElement *player;
	std::string cur_file;
	bool change_state(GstState state);

public:
	/**
	 * GStreamer audio driver constructor.
	 */
	GSTDriver(int *, char ***);

	/**
	 * GStreamer audio driver destructor.
	 */
	~GSTDriver();

	/**
	 * Called to initialize the GStreamer audio driver.
	 * @param  eos_cb  End-of-stream callback function.
	 */
	void init(void (*)());

	/**
	 * Load a track into the gstreamer pipeline.
	 * @param  filepath  The file to be loaded.
	 */
	void load(const std::string &);

	/**
	 * Begin playback on the GStreamer pipeline.
	 * @return True if the state change was successful.
	 */
	bool play();

	/**
	 * Pause the GStreamer pipeline.
	 * @return True if the state change was successful.
	 */
	bool pause();

	/**
	 * Check if the GStreamer pipeline is playing.
	 * @return True if the pipeline is playing.
	 */
	bool is_playing();


	/**
	 * Seek to a specific position in the pipeline.
	 * @param  offset  Offset from the beginning of the pipeline, in nanoseconds.
	 */
	void seek_to(long);

	/**
	 * Find the current playback position of the pipeline.
	 * @return The current position of the pipeline, in nanoseconds.
	 */
	long position();

	/**
	 * Find the duration of the pipeline.
	 * @return The duration of the pipeline, in nanoseconds.
	 */
	long duration();


	/**
	 * Called to handle messages from the GStreamer bus.
	 * @param  message  The message to be handled.
	 */
	void on_message(GstMessage *);
};


static gboolean on_gst_message(GstBus *bus, GstMessage *message, gpointer data)
{
	GSTDriver *driver = (GSTDriver *)data;
	driver->on_message(message);
	return TRUE;
}

static void parse_gst_error(GstMessage *error, const std::string filepath)
{
	GError *err;
	gchar  *debug;

	gst_message_parse_error(error, &err, &debug);
	g_print("Error playing file: %s\n", filepath.c_str());
	g_print("Error: %s\n", err->message);
	g_error_free(err);
	g_free(debug);
}

GSTDriver :: GSTDriver(int *argc, char ***argv)
	   : Driver()
{
	GstBus *bus;

	gst_init(argc, argv);
	player = gst_element_factory_make("playbin", "ocarina_player");
	bus    = gst_pipeline_get_bus(GST_PIPELINE(player));
	gst_bus_add_watch(bus, on_gst_message, this);
}

GSTDriver :: ~GSTDriver()
{
	change_state(GST_STATE_NULL);
	gst_deinit();
}

bool GSTDriver :: change_state(GstState state)
{
	GstStateChangeReturn ret = gst_element_set_state(player, state);
	switch (ret) {
	case GST_STATE_CHANGE_SUCCESS:
	case GST_STATE_CHANGE_ASYNC:
		return true;
	default:
		return false;
	}
}

void GSTDriver :: init(void (*eos_cb)())
{
	on_eos   = eos_cb;
}

void GSTDriver :: load(const std::string &filepath)
{
	gchar *uri;

	cur_file = filepath;
	change_state(GST_STATE_NULL);
	uri = gst_filename_to_uri(filepath.c_str(), NULL);
	g_object_set(G_OBJECT(player), "uri", uri, NULL);
	g_free(uri);
}

bool GSTDriver :: play()
{
	return change_state(GST_STATE_PLAYING);
}

bool GSTDriver :: pause()
{
	return change_state(GST_STATE_PAUSED);
}

bool GSTDriver :: is_playing()
{
	GstState state;
	gst_element_get_state(player, &state, NULL, GST_CLOCK_TIME_NONE);
	return state == GST_STATE_PLAYING;
}

void GSTDriver :: seek_to(long offset)
{
	gst_element_seek_simple(player, GST_FORMAT_TIME, GST_SEEK_FLAG_FLUSH, offset);
}

long GSTDriver :: position()
{
	long position;
	if (gst_element_query_position(player, GST_FORMAT_TIME, &position))
		return position;
	return 0;
}

long GSTDriver :: duration()
{
	long duration;

	if (gst_element_query_duration(player, GST_FORMAT_TIME, &duration))
		return duration;
	return 0;
}

void GSTDriver :: on_message(GstMessage *message)
{
	switch (GST_MESSAGE_TYPE(message)) {
	case GST_MESSAGE_ERROR:
		parse_gst_error(message, cur_file);
		audio :: next();
		break;
	case GST_MESSAGE_EOS:
		on_eos();
		break;
	default:
		break;
	}
}


void init_gst(int *argc, char ***argv)
{
	gst_driver = new GSTDriver(argc, argv);
}

void quit_gst()
{
	delete gst_driver;
}