Added measures and beats to the playondemand filter so it can act like an audio sequencer. Currently defines three ex...

Original commit message from CVS:
Added measures and beats to the playondemand filter so it can act like an audio
sequencer. Currently defines three extra globally visible functions, might
eventually want to put them in an interface instead ?

5 files changed, 458 insertions, 160 deletions

diff --git a/gst/playondemand/Makefile.am b/gst/playondemand/Makefile.am
index 63052ac1..43f12140 100644
--- a/gst/playondemand/Makefile.am
+++ b/gst/playondemand/Makefile.am
@@ -13,8 +13,7 @@ if HAVE_GTK
 noinst_PROGRAMS = demo_mp3
 endif
 
-demo_mp3_SOURCES = demo-mp3.c
+demo_mp3_SOURCES = demo-mp3.c gstplayondemand.h
 ## putting GTK_CFLAGS first fixes a weird compilation error with GTK and XML
 demo_mp3_CFLAGS  = $(GTK_CFLAGS) $(GST_CFLAGS)
-demo_mp3_LDFLAGS = $(GST_LIBS) $(GTK_LIBS)
-
+demo_mp3_LDFLAGS = $(GST_LIBS) $(GTK_LIBS) ./libgstplayondemand.la
diff --git a/gst/playondemand/demo-mp3.c b/gst/playondemand/demo-mp3.c
index 91b9e3bf..2bb2005c 100644
--- a/gst/playondemand/demo-mp3.c
+++ b/gst/playondemand/demo-mp3.c
@@ -3,80 +3,140 @@
 #include <gtk/gtk.h>
 #include <gst/gst.h>
 
-void play (GtkButton *button, gpointer data)
+#include "gstplayondemand.h"
+
+guint channels;
+GtkWidget *window, *vbox, *play_button, *reset_button, *quit_button;
+GtkWidget *hbox, *measure1_button, *measure2_button, *measure3_button, \
+  *measure4_button, *measure5_button, *measure6_button, *speed_scale;
+GstElement *src, *mad, *pod, *osssink, *pipeline;
+GstClock *element_clock;
+
+void
+play (GtkButton *button, gpointer data)
 {
-  g_signal_emit_by_name(G_OBJECT(data), "play", NULL, NULL);
+  g_signal_emit_by_name(G_OBJECT(pod), "play", NULL, NULL);
 }
-  
-void reset (GtkButton *button, gpointer data)
+
+void
+reset (GtkButton *button, gpointer data)
 {
-  g_signal_emit_by_name(G_OBJECT(data), "reset", NULL, NULL);
+  g_signal_emit_by_name(G_OBJECT(pod), "reset", NULL, NULL);
 }
-  
-int main(int argc, char **argv) 
+
+void
+measure (GtkToggleButton *button, gpointer data)
+{
+  gst_play_on_demand_toggle_beat(GST_PLAYONDEMAND(pod),
+                                 GPOINTER_TO_UINT(data), 0);
+}
+
+void
+speed (GtkAdjustment *scale, gpointer data)
+{
+  gst_clock_set_speed(element_clock, gtk_adjustment_get_value(scale));
+}
+
+void
+setup_pipeline (gchar *filename)
 {
-  guint channels;
-  GtkWidget *window, *vbox, *play_button, *reset_button, *quit_button;
-  GstElement *src, *mad, *pod, *osssink, *pipeline;
-    
-  gst_init (&argc, &argv);
-  gtk_init (&argc, &argv);
-    
-  if (argc!=2) {
-    g_print("usage: %s <mp3-filename>\n", argv[0]);
-    exit(-1);
-  }
-    
   src = gst_element_factory_make("filesrc", "filesrc");
   mad = gst_element_factory_make("mad", "mad");
   pod = gst_element_factory_make("playondemand", "playondemand");
   osssink = gst_element_factory_make("osssink", "osssink");
 
-  g_object_set(G_OBJECT(src), "location", argv[1], NULL);
+  g_object_set(G_OBJECT(src), "location", filename, NULL);
+  g_object_set(G_OBJECT(pod), "silent", FALSE, NULL);
   g_object_set(G_OBJECT(osssink), "fragment", 0x00180008, NULL);
   g_object_get(G_OBJECT(osssink), "channels", &channels, NULL);
 
   pipeline = gst_pipeline_new("app");
 
-  gst_bin_add(GST_BIN(pipeline), src);
-  gst_bin_add(GST_BIN(pipeline), mad);
-  gst_bin_add(GST_BIN(pipeline), pod);
-  gst_bin_add(GST_BIN(pipeline), osssink);
-
-  gst_element_connect(src, mad);
-  gst_element_connect(pod, osssink);
-  gst_element_connect(mad, pod);
+  gst_bin_add_many(GST_BIN(pipeline), src, mad, pod, osssink, NULL);
+  gst_element_connect_many(src, mad, pod, osssink, NULL);
 
-  gst_element_set_state(pipeline, GST_STATE_PLAYING);
+  element_clock = gst_bin_get_clock(GST_BIN(pipeline));
+  gst_element_set_clock(GST_ELEMENT(pod), element_clock);
+  /* gst_clock_set_speed(element_clock, 0.00001); */
+}
 
+void
+setup_gui (void)
+{
   /* initialize gui elements ... */
   window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
-  vbox = gtk_vbox_new(FALSE, 0);
+  vbox = gtk_vbox_new(TRUE, 0);
+  hbox = gtk_hbox_new(TRUE, 0);
   play_button = gtk_button_new_with_label("play");
   reset_button = gtk_button_new_with_label("reset");
   quit_button = gtk_button_new_with_label("quit");
+  measure1_button = gtk_toggle_button_new_with_label("one");
+  measure2_button = gtk_toggle_button_new_with_label("two");
+  measure3_button = gtk_toggle_button_new_with_label("three");
+  measure4_button = gtk_toggle_button_new_with_label("four");
+  measure5_button = gtk_toggle_button_new_with_label("five");
+  measure6_button = gtk_toggle_button_new_with_label("six");
+  speed_scale = gtk_hscale_new_with_range(0.0, 0.001, 0.000001);
+  /*  gtk_adjustment_set_value(GTK_ADJUSTMENT(speed_scale), 0.00001); */
 
   /* do the packing stuff ... */
   gtk_window_set_default_size(GTK_WINDOW(window), 96, 96);
   gtk_container_add(GTK_CONTAINER(window), vbox);
-  gtk_box_pack_start(GTK_BOX(vbox), play_button, FALSE, FALSE, 2);
-  gtk_box_pack_start(GTK_BOX(vbox), reset_button, FALSE, FALSE, 2);
-  gtk_box_pack_start(GTK_BOX(vbox), quit_button, FALSE, FALSE, 2);
+  gtk_box_pack_start(GTK_BOX(vbox), play_button, TRUE, FALSE, 2);
+  gtk_box_pack_start(GTK_BOX(vbox), reset_button, TRUE, FALSE, 2);
+  gtk_box_pack_start(GTK_BOX(vbox), hbox, TRUE, FALSE, 2);
+  gtk_box_pack_start(GTK_BOX(hbox), measure1_button, TRUE, TRUE, 2);
+  gtk_box_pack_start(GTK_BOX(hbox), measure2_button, TRUE, TRUE, 2);
+  gtk_box_pack_start(GTK_BOX(hbox), measure3_button, TRUE, TRUE, 2);
+  gtk_box_pack_start(GTK_BOX(hbox), measure4_button, TRUE, TRUE, 2);
+  gtk_box_pack_start(GTK_BOX(hbox), measure5_button, TRUE, TRUE, 2);
+  gtk_box_pack_start(GTK_BOX(hbox), measure6_button, TRUE, TRUE, 2);
+  /*gtk_box_pack_start(GTK_BOX(vbox), speed_scale, TRUE, FALSE, 2);*/
+  gtk_box_pack_start(GTK_BOX(vbox), quit_button, TRUE, FALSE, 2);
 
   /* connect things ... */
-  g_signal_connect(G_OBJECT(play_button), "clicked", G_CALLBACK(play), pod);
-  g_signal_connect(G_OBJECT(reset_button), "clicked", G_CALLBACK(reset), pod);
+  g_signal_connect(G_OBJECT(play_button), "clicked", G_CALLBACK(play), NULL);
+  g_signal_connect(G_OBJECT(reset_button), "clicked", G_CALLBACK(reset), NULL);
   g_signal_connect(G_OBJECT(quit_button), "clicked", gtk_main_quit, NULL);
+  g_signal_connect(G_OBJECT(measure1_button), "toggled", G_CALLBACK(measure), GUINT_TO_POINTER(0));
+  g_signal_connect(G_OBJECT(measure2_button), "toggled", G_CALLBACK(measure), GUINT_TO_POINTER(1));
+  g_signal_connect(G_OBJECT(measure3_button), "toggled", G_CALLBACK(measure), GUINT_TO_POINTER(2));
+  g_signal_connect(G_OBJECT(measure4_button), "toggled", G_CALLBACK(measure), GUINT_TO_POINTER(3));
+  g_signal_connect(G_OBJECT(measure5_button), "toggled", G_CALLBACK(measure), GUINT_TO_POINTER(4));
+  g_signal_connect(G_OBJECT(measure6_button), "toggled", G_CALLBACK(measure), GUINT_TO_POINTER(5));
+  /*g_signal_connect(G_OBJECT(speed_scale), "value-changed", G_CALLBACK(speed), NULL);*/
 
   /* show the gui. */
   gtk_widget_show(play_button);
   gtk_widget_show(reset_button);
   gtk_widget_show(quit_button);
+  gtk_widget_show(measure1_button);
+  gtk_widget_show(measure2_button);
+  gtk_widget_show(measure3_button);
+  gtk_widget_show(measure4_button);
+  gtk_widget_show(measure5_button);
+  gtk_widget_show(measure6_button);
+  gtk_widget_show(hbox);
+  /*gtk_widget_show(speed_scale);*/
   gtk_widget_show(vbox);
   gtk_widget_show(window);
   gtk_idle_add((GtkFunction)gst_bin_iterate, pipeline);
-    
-  gtk_main();
+}
+
+int
+main(int argc, char **argv)
+{
+  gst_init (&argc, &argv);
+  gtk_init (&argc, &argv);
+
+  if (argc!=2) {
+    g_print("usage: %s <mp3-filename>\n", argv[0]);
+    exit(-1);
+  }
 
+  setup_pipeline(argv[1]);
+  gst_element_set_state(pipeline, GST_STATE_PLAYING);
+  setup_gui();
+  gtk_main();
   return 0;
 }
diff --git a/gst/playondemand/filter.func b/gst/playondemand/filter.func
index 091626b2..2d77189f 100644
--- a/gst/playondemand/filter.func
+++ b/gst/playondemand/filter.func
@@ -4,6 +4,7 @@ _TYPE_ *data_in, *data_out, *filter_data;
 
 filter_data = (_TYPE_ *) filter->buffer;
 num_filter = filter->buffer_size / sizeof(_TYPE_);
+max_filter = (filter->play_from_beginning) ? num_filter : G_MAXUINT;
 
 /******************************************************************************/
 /* see if we've got any events coming through ... */
@@ -21,7 +22,7 @@ do {
     in = gst_pad_pull(filter->sinkpad);
   }
 
-  /******************************************************************************/
+  /****************************************************************************/
   /* first handle data from the input buffer. */
 
   GST_DEBUG(0, "--- done with events, going to input");
@@ -34,44 +35,47 @@ do {
     w = filter->write;
 
     /* copy the input data to the filter's internal buffer. */
-    if (filter->follow_stream_tail) {
-      for (j = 0; j < num_in; j++) {
-        filter_data[(w + j) % num_filter] = data_in[j];
-      }
+    for (j = 0; (j < num_in) && ((w + j) < max_filter); j++) {
+      filter_data[(w + j) % num_filter] = data_in[j];
+    }
 
-      filter->write = (w + j) % num_filter;
-      
-      /* update the start pointer */
-      if ((filter->start != 0) || ((w + j) >= num_filter)) {
-        filter->start = (filter->write + 1) % num_filter;
-      }
-    } else {
-      for (j = 0; (j < num_in) && ((w + j) < num_filter); j++) {
-        filter_data[w + j] = data_in[j];
-      }
+    filter->write = (w + j) % num_filter;
 
-      filter->write += j;
+    if ((w + j) >= num_filter) {
+      filter->buffer_filled_once = TRUE;
 
-      /* if we're not following the stream tail, the buffer is just a straight
-         buffer. so we need to set eos if we've passed the limit of the internal
-         buffer size. */
-      if ((w + j) >= num_filter) {
+      /* if we're not playing from the end of the stream, the buffer is not a
+         ring buffer, so it has a fixed size. we need to set eos here because
+         we've passed that limit. */
+      if (filter->play_from_beginning) {
         filter->eos = TRUE;
       }
     }
 
+    /* update the start pointer */
+    if ((! filter->play_from_beginning) && filter->buffer_filled_once) {
+      filter->start = (filter->write + 1) % num_filter;
+    }
+
     out = in;
   } else {
-    j = 0;
+    j = num_filter;
     w = 0;
-    
+
     out = gst_buffer_new_from_pool(filter->bufpool, 0, 0);
   }
 
-  /******************************************************************************/
+  /****************************************************************************/
+  /* check to see if we have to add a new play pointer. */
+
+  GST_DEBUG(0, "--- done with input, checking clock before output");
+
+  play_on_demand_update_plays_from_clock(filter);
+
+  /****************************************************************************/
   /* now handle output data. */
 
-  GST_DEBUG(0, "--- done with input, going to output");
+  GST_DEBUG(0, "--- done with clock, going to output");
 
   data_out = (_TYPE_ *) GST_BUFFER_DATA(out);
   num_out = GST_BUFFER_SIZE(out) / sizeof(_TYPE_);
@@ -79,30 +83,33 @@ do {
   for (k = 0; k < num_out; k++) {
     data_out[k] = zero;
   }
-  
+
   /* output play pointer data. */
-  for (t = 0; t < POD_MAX_PLAYS; t++) {
+  for (t = 0; t < GST_POD_MAX_PLAY_PTRS; t++) {
     offset = filter->plays[t];
 
     if (offset != G_MAXUINT) {
-      if (filter->follow_stream_tail) {
+      if (! filter->play_from_beginning) {
         for (k = 0; k < num_out; k++) {
           data_out[k] = CLAMP(data_out[k] + filter_data[(offset + k) % num_filter], min, max);
         }
       } else {
-        for (k = 0; (k < num_out) && ((offset + k) < (w + j)); k++) {
+        for (k = 0; (k < num_out) && (k < (w + j - offset)); k++) {
           data_out[k] = CLAMP(data_out[k] + filter_data[offset + k], min, max);
         }
       }
 
-      if ((offset < w) && ((offset + k) >= (w + j))) {
-        filter->plays[t] = G_MAXUINT;
+      if ((! filter->play_from_beginning) || ((offset + k) < (w + j))) {
+        filter->plays[t] = (offset + k) % num_filter;
       } else {
-        filter->plays[t] = (filter->plays[t] + k) % num_filter;
+        filter->plays[t] = G_MAXUINT;
       }
     }
   }
 
+  /****************************************************************************/
+  /* push out the buffer. */
+
   GST_DEBUG(0, "--- done with output, pushing buffer %p", out);
 
   gst_pad_push(filter->srcpad, out);
@@ -110,6 +117,7 @@ do {
   if (! filter->eos) {
     in = gst_pad_pull(filter->sinkpad);
   }
+
   gst_element_yield (GST_ELEMENT (filter));
 
 } while (TRUE);
diff --git a/gst/playondemand/gstplayondemand.c b/gst/playondemand/gstplayondemand.c
index 45814382..0e8266b2 100644
--- a/gst/playondemand/gstplayondemand.c
+++ b/gst/playondemand/gstplayondemand.c
@@ -23,23 +23,25 @@
 #include "gstplayondemand.h"
 
 
-#define POD_MAX_PLAYS     192     /* maximum number of simultaneous plays */
-#define POD_BUFPOOL_SIZE  4096    /* gstreamer buffer size to make if no
+#define GST_POD_MAX_PLAY_PTRS 128     /* maximum number of simultaneous plays */
+#define GST_POD_NUM_MEASURES  8       /* default number of measures */
+#define GST_POD_NUM_BEATS     16      /* default number of beats in a measure */
+#define GST_POD_BUFPOOL_SIZE  4096    /* gstreamer buffer size to use if no
                                      bufferpool is available, must be divisible
                                      by sizeof(gfloat) */
-#define POD_BUFPOOL_NUM   6       /* number of buffers to allocate per chunk in
+#define GST_POD_BUFPOOL_NUM   6       /* number of buffers to allocate per chunk in
                                      sink buffer pool */
-#define POD_BUFFER_SIZE   882000  /* enough space for 10 seconds of 16-bit audio
-                                     at 44100 samples per second ... */
+#define GST_POD_BUFFER_SIZE   882000  /* enough space for 5 seconds of 32-bit float
+                                     audio at 44100 samples per second ... */
 
 /* elementfactory information */
 static GstElementDetails play_on_demand_details = {
   "Play On Demand",
   "Filter/Audio/Effect",
   "LGPL",
-  "Plays a stream whenever it receives a certain signal",
+  "Plays a stream at specific times, or when it receives a signal",
   VERSION,
-  "Leif Morgan Johnson <lmjohns3@eos.ncsu.edu>",
+  "Leif Morgan Johnson <leif@ambient.2y.net>",
   "(C) 2001",
 };
 
@@ -55,58 +57,71 @@ enum {
 static guint gst_pod_filter_signals[LAST_SIGNAL] = { 0 };
 
 enum {
-  ARG_0,
-  ARG_SILENT,
-  ARG_FOLLOWTAIL,
-  ARG_BUFFERSIZE
+  PROP_0,
+  PROP_SILENT,
+  PROP_PLAYFROMBEGINNING,
+  PROP_BUFFERSIZE,
+  PROP_NUM_BEATS,
+  PROP_NUM_MEASURES
 };
 
-static GstPadTemplate*                    
-play_on_demand_sink_factory (void)            
-{                                         
-  static GstPadTemplate *template = NULL; 
-                                          
-  if (!template) {                        
-    template = gst_pad_template_new 
+static GstPadTemplate*
+play_on_demand_sink_factory (void)
+{
+  static GstPadTemplate *template = NULL;
+
+  if (!template) {
+    template = gst_pad_template_new
       ("sink", GST_PAD_SINK, GST_PAD_ALWAYS,
       gst_caps_append(gst_caps_new ("sink_int",  "audio/raw",
                                     GST_AUDIO_INT_PAD_TEMPLATE_PROPS),
                       gst_caps_new ("sink_float", "audio/raw",
                                     GST_AUDIO_FLOAT_MONO_PAD_TEMPLATE_PROPS)),
       NULL);
-  }                                       
-  return template;                        
+  }
+  return template;
 }
 
 static GstPadTemplate*
 play_on_demand_src_factory (void)
 {
   static GstPadTemplate *template = NULL;
-  
+
   if (!template)
-    template = gst_pad_template_new 
+    template = gst_pad_template_new
       ("src", GST_PAD_SRC, GST_PAD_ALWAYS,
        gst_caps_append (gst_caps_new ("src_float", "audio/raw",
                                       GST_AUDIO_FLOAT_MONO_PAD_TEMPLATE_PROPS),
                         gst_caps_new ("src_int", "audio/raw",
                                       GST_AUDIO_INT_PAD_TEMPLATE_PROPS)),
        NULL);
-  
+
   return template;
 }
 
-static void	play_on_demand_class_init	(GstPlayOnDemandClass *klass);
-static void	play_on_demand_init		(GstPlayOnDemand *filter);
+static void play_on_demand_class_init   (GstPlayOnDemandClass *klass);
+static void play_on_demand_init         (GstPlayOnDemand *filter);
+
+static void play_on_demand_set_property (GObject *object,
+                                         guint prop_id,
+                                         const GValue *value,
+                                         GParamSpec *pspec);
+static void play_on_demand_get_property (GObject *object,
+                                         guint prop_id,
+                                         GValue *value,
+                                         GParamSpec *pspec);
 
-static void	play_on_demand_set_property	(GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec);
-static void	play_on_demand_get_property	(GObject *object, guint prop_id, GValue *value, GParamSpec *pspec);
+static GstPadConnectReturn play_on_demand_pad_connect (GstPad *pad, GstCaps *caps);
 
-static GstPadConnectReturn	play_on_demand_pad_connect	(GstPad *pad, GstCaps *caps);
+static void play_on_demand_loop         (GstElement *elem);
 
-static void	play_on_demand_loop		(GstElement *elem);
+static void play_on_demand_set_clock    (GstElement *elem, GstClock *clock);
 
-static void	play_on_demand_play_handler	(GstElement *elem);
-static void	play_on_demand_reset_handler	(GstElement *elem);
+static void play_on_demand_play_handler  (GstElement *elem);
+static void play_on_demand_add_play_ptr  (GstPlayOnDemand *filter, guint pos);
+static void play_on_demand_reset_handler (GstElement *elem);
+
+static void play_on_demand_update_plays_from_clock (GstPlayOnDemand *filter);
 
 static GstElementClass *parent_class = NULL;
 
@@ -125,17 +140,17 @@ play_on_demand_pad_connect (GstPad *pad, GstCaps *caps)
 {
   const gchar *format;
   GstPlayOnDemand *filter;
-  
+
   g_return_val_if_fail(caps != NULL, GST_PAD_CONNECT_DELAYED);
   g_return_val_if_fail(pad  != NULL, GST_PAD_CONNECT_DELAYED);
 
   filter = GST_PLAYONDEMAND(GST_PAD_PARENT(pad));
 
   gst_caps_get_string(caps, "format", &format);
-  
+
   gst_caps_get_int(caps, "rate",     &filter->rate);
   gst_caps_get_int(caps, "channels", &filter->channels);
-  
+
   if (strcmp(format, "int") == 0) {
     filter->format     = GST_PLAYONDEMAND_FORMAT_INT;
     gst_caps_get_int     (caps, "width",      &filter->width);
@@ -145,23 +160,30 @@ play_on_demand_pad_connect (GstPad *pad, GstCaps *caps)
     gst_caps_get_boolean (caps, "signed",     &filter->is_signed);
 
     if (!filter->silent) {
-      g_print ("PlayOnDemand : channels %d, rate %d\n",  
+      g_print ("PlayOnDemand : channels %d, rate %d\n",
                filter->channels, filter->rate);
       g_print ("PlayOnDemand : format int, bit width %d, endianness %d, signed %s\n",
                filter->width, filter->endianness, filter->is_signed ? "yes" : "no");
     }
-  } else if (strcmp(format, "float") == 0) {
+
+    filter->buffer_samples = filter->buffer_size;
+    filter->buffer_samples /= (filter->width) ? filter->width / 8 : 1;
+    filter->buffer_samples /= (filter->channels) ? filter->channels : 1;
+} else if (strcmp(format, "float") == 0) {
     filter->format     = GST_PLAYONDEMAND_FORMAT_FLOAT;
     gst_caps_get_string (caps, "layout",    &filter->layout);
     gst_caps_get_float  (caps, "intercept", &filter->intercept);
     gst_caps_get_float  (caps, "slope",     &filter->slope);
 
     if (!filter->silent) {
-      g_print ("PlayOnDemand : channels %d, rate %d\n",  
+      g_print ("PlayOnDemand : channels %d, rate %d\n",
                filter->channels, filter->rate);
       g_print ("PlayOnDemand : format float, layout %s, intercept %f, slope %f\n",
                filter->layout, filter->intercept, filter->slope);
     }
+
+    filter->buffer_samples = filter->buffer_size / sizeof(gfloat);
+    filter->buffer_samples /= (filter->channels) ? filter->channels : 1;
   }
 
   if (GST_CAPS_IS_FIXED (caps))
@@ -186,7 +208,9 @@ gst_play_on_demand_get_type (void)
       0,
       (GInstanceInitFunc) play_on_demand_init,
     };
-    play_on_demand_type = g_type_register_static(GST_TYPE_ELEMENT, "GstPlayOnDemand", &play_on_demand_info, 0);
+    play_on_demand_type = g_type_register_static(GST_TYPE_ELEMENT,
+                                                 "GstPlayOnDemand",
+                                                 &play_on_demand_info, 0);
   }
   return play_on_demand_type;
 }
@@ -223,17 +247,25 @@ play_on_demand_class_init (GstPlayOnDemandClass *klass)
 
   parent_class = g_type_class_ref(GST_TYPE_ELEMENT);
 
-  g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_SILENT,
+  g_object_class_install_property(G_OBJECT_CLASS(klass), PROP_SILENT,
     g_param_spec_boolean("silent","silent","silent",
                          TRUE, G_PARAM_READWRITE));
 
-  g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_FOLLOWTAIL,
-    g_param_spec_boolean("follow-stream-tail","follow-stream-tail","follow-stream-tail",
-                         FALSE, G_PARAM_READWRITE));
+  g_object_class_install_property(G_OBJECT_CLASS(klass), PROP_PLAYFROMBEGINNING,
+    g_param_spec_boolean("play-from-beginning","play-from-beginning","play-from-beginning",
+                         TRUE, G_PARAM_READWRITE));
 
-  g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_BUFFERSIZE,
+  g_object_class_install_property(G_OBJECT_CLASS(klass), PROP_BUFFERSIZE,
     g_param_spec_uint("buffer-size","buffer-size","buffer-size",
-                      0, G_MAXUINT - 1, POD_BUFFER_SIZE, G_PARAM_READWRITE));
+                      0, G_MAXUINT - 1, GST_POD_BUFFER_SIZE, G_PARAM_READWRITE));
+
+  g_object_class_install_property(G_OBJECT_CLASS(klass), PROP_NUM_BEATS,
+    g_param_spec_uint("num-beats","num-beats","num-beats",
+                      0, G_MAXUINT - 1, GST_POD_NUM_BEATS, G_PARAM_READWRITE));
+
+  g_object_class_install_property(G_OBJECT_CLASS(klass), PROP_NUM_MEASURES,
+    g_param_spec_uint("num-measures","num-measures","num-measures",
+                      0, G_MAXUINT - 1, GST_POD_NUM_MEASURES, G_PARAM_READWRITE));
 
   gobject_class->set_property = play_on_demand_set_property;
   gobject_class->get_property = play_on_demand_get_property;
@@ -243,32 +275,44 @@ static void
 play_on_demand_init (GstPlayOnDemand *filter)
 {
   guint i;
-  
+
   filter->srcpad = gst_pad_new_from_template(play_on_demand_src_factory(), "src");
   filter->sinkpad = gst_pad_new_from_template(play_on_demand_sink_factory(), "sink");
 
   gst_pad_set_bufferpool_function(filter->sinkpad, play_on_demand_get_bufferpool);
   gst_pad_set_connect_function(filter->sinkpad, play_on_demand_pad_connect);
-  
+
   gst_element_add_pad(GST_ELEMENT(filter), filter->sinkpad);
   gst_element_add_pad(GST_ELEMENT(filter), filter->srcpad);
 
   gst_element_set_loop_function(GST_ELEMENT(filter), play_on_demand_loop);
 
-  filter->follow_stream_tail = FALSE;  
-  filter->silent      = TRUE;
-
-  filter->buffer      = g_new(gchar, POD_BUFFER_SIZE);
-  filter->buffer_size = POD_BUFFER_SIZE;
+  filter->buffer      = g_new(gchar, GST_POD_BUFFER_SIZE);
+  filter->buffer_size = GST_POD_BUFFER_SIZE;
   filter->start       = 0;
   filter->write       = 0;
 
-  filter->eos         = FALSE;
+  filter->eos                 = FALSE;
+  filter->buffer_filled_once  = FALSE;
+  filter->play_from_beginning = TRUE;
+  filter->silent              = TRUE;
+
+  GST_ELEMENT (filter)->setclockfunc = play_on_demand_set_clock;
+  filter->clock       = NULL;
+  filter->last_time   = 0;
+
+  filter->num_beats    = GST_POD_NUM_BEATS;
+  filter->num_measures = GST_POD_NUM_MEASURES;
+  filter->total_beats  = filter->num_beats * filter->num_measures;
+  filter->times = g_new(guint64, filter->num_measures);
+  for (i = 0; i < filter->num_measures; i++) {
+    filter->times[i] = 0;
+  }
 
   /* the plays are stored as an array of buffer offsets. this initializes the
-     array to `blank' values (G_MAXUINT is an invalid index for this filter). */
-  filter->plays  = g_new(guint, POD_MAX_PLAYS);
-  for (i = 0; i < POD_MAX_PLAYS; i++) {
+     array to `blank' values (G_MAXUINT is the `invalid' index). */
+  filter->plays  = g_new(guint, GST_POD_MAX_PLAY_PTRS);
+  for (i = 0; i < GST_POD_MAX_PLAY_PTRS; i++) {
     filter->plays[i] = G_MAXUINT;
   }
 }
@@ -277,18 +321,19 @@ static void
 play_on_demand_loop (GstElement *elem)
 {
   GstPlayOnDemand *filter = GST_PLAYONDEMAND(elem);
-  guint            num_in, num_out, num_filter;
+  guint            num_in, num_out, num_filter, max_filter;
   GstBuffer       *in, *out;
   register guint   j, k, t;
   guint            w, offset;
-  
+
   g_return_if_fail(filter != NULL);
   g_return_if_fail(GST_IS_PLAYONDEMAND(filter));
 
   filter->bufpool = gst_pad_get_bufferpool(filter->srcpad);
 
   if (filter->bufpool == NULL) {
-    filter->bufpool = gst_buffer_pool_get_default(POD_BUFPOOL_SIZE, POD_BUFPOOL_NUM);
+    filter->bufpool = gst_buffer_pool_get_default(GST_POD_BUFPOOL_SIZE,
+                                                  GST_POD_BUFPOOL_NUM);
   }
 
   in = gst_pad_pull(filter->sinkpad);
@@ -320,15 +365,37 @@ play_on_demand_loop (GstElement *elem)
 }
 
 static void
-play_on_demand_play_handler(GstElement *elem)
+play_on_demand_set_clock (GstElement *elem, GstClock *clock)
+{
+  GstPlayOnDemand *filter;
+  g_return_if_fail(GST_IS_PLAYONDEMAND(elem));
+  filter = GST_PLAYONDEMAND(elem);
+  g_return_if_fail(filter != NULL);
+
+  filter->clock = clock;
+}
+
+static void
+play_on_demand_play_handler (GstElement *elem)
+{
+  GstPlayOnDemand *filter;
+
+  g_return_if_fail(GST_IS_PLAYONDEMAND(elem));
+  filter = GST_PLAYONDEMAND(elem);
+  g_return_if_fail(filter != NULL);
+
+  play_on_demand_add_play_ptr(filter, filter->start);
+}
+
+static void
+play_on_demand_add_play_ptr (GstPlayOnDemand *filter, guint pos)
 {
-  GstPlayOnDemand *filter = GST_PLAYONDEMAND(elem);
   register guint i;
 
-  for (i = 0; i < POD_MAX_PLAYS; i++) {
+  for (i = 0; i < GST_POD_MAX_PLAY_PTRS; i++) {
     if (filter->plays[i] == G_MAXUINT) {
-      filter->plays[i] = filter->start;
-      break;
+      filter->plays[i] = pos;
+      return;
     }
   }
 }
@@ -336,42 +403,178 @@ play_on_demand_play_handler(GstElement *elem)
 static void
 play_on_demand_reset_handler(GstElement *elem)
 {
-  GstPlayOnDemand *filter = GST_PLAYONDEMAND(elem);
+  GstPlayOnDemand *filter;
   register guint i;
-  
-  for (i = 0; i < POD_MAX_PLAYS; i++) {
+
+  g_return_if_fail(GST_IS_PLAYONDEMAND(elem));
+  filter = GST_PLAYONDEMAND(elem);
+  g_return_if_fail(filter != NULL);
+
+  for (i = 0; i < GST_POD_MAX_PLAY_PTRS; i++) {
     filter->plays[i] = G_MAXUINT;
   }
 
   filter->start = 0;
   filter->write = 0;
+  filter->eos = FALSE;
+  filter->buffer_filled_once = FALSE;
+
+  for (i = 0; i < filter->num_measures; i++) {
+    filter->times[i] = 0;
+  }
 }
 
+#define GST_POD_SAMPLE_OFFSET(f, dt) (((f)->start - ((dt) / (f)->rate)) % (f)->buffer_samples)
+
 static void
-play_on_demand_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec)
+play_on_demand_update_plays_from_clock(GstPlayOnDemand *filter)
+{
+  register guint t;
+  guint          total, beats, last, time;
+
+  g_return_if_fail(GST_IS_PLAYONDEMAND(filter));
+  g_return_if_fail(filter != NULL);
+
+  if (filter->clock) {
+    total = filter->total_beats;
+    beats = filter->num_beats;
+
+    last = filter->last_time;
+    time = (guint) ((gst_clock_get_time(filter->clock) / 10000000LL) % total);
+    filter->last_time = time;
+
+    GST_DEBUG(0, "--- clock time %u, last %u, total %u", time, last, total);
+
+    /* if the current time is less than the last time, the clock has wrapped
+       around the total number of beats ... we need to count back to 0 and then
+       wrap around to the end. */
+    if (time < last) {
+      for (t = time; t != G_MAXUINT; t--) {
+        if (filter->times[t / beats] & ((guint64) 1 << (t % beats))) {
+          play_on_demand_add_play_ptr(filter,
+                                      GST_POD_SAMPLE_OFFSET(filter, time - t));
+        }
+      }
+
+      time = total - 1;
+    }
+
+    for (t = time; t > last; t--) {
+      if (filter->times[t / beats] & ((guint64) 1 << (t % beats))) {
+        play_on_demand_add_play_ptr(filter,
+                                    GST_POD_SAMPLE_OFFSET(filter, time - t));
+      }
+    }
+  }
+}
+
+void
+gst_play_on_demand_set_beat(GstPlayOnDemand *filter, const guint measure,
+                            const guint beat, const gboolean value)
+{
+  g_return_if_fail(GST_IS_PLAYONDEMAND(filter));
+  g_return_if_fail(filter != NULL);
+  g_return_if_fail(filter->num_measures > measure);
+  g_return_if_fail(filter->total_beats < (filter->num_beats * measure + beat));
+
+  if (value) {
+    filter->times[measure] |= (1 << beat);
+  } else {
+    filter->times[measure] &= (((guint64) -1) ^ (1 << beat));
+  }
+}
+
+gboolean
+gst_play_on_demand_get_beat(GstPlayOnDemand *filter, const guint measure,
+                            const guint beat)
+{
+  g_return_val_if_fail(GST_IS_PLAYONDEMAND(filter), FALSE);
+  g_return_val_if_fail(filter != NULL, FALSE);
+  g_return_val_if_fail(filter->num_measures > measure, FALSE);
+  g_return_val_if_fail(filter->total_beats >
+                       (filter->num_beats * measure + beat), FALSE);
+
+  return ((filter->times[measure] >> beat) & ((guint64) 1));
+}
+
+void
+gst_play_on_demand_toggle_beat(GstPlayOnDemand *filter, const guint measure,
+                               const guint beat)
+{
+  g_return_if_fail(GST_IS_PLAYONDEMAND(filter));
+  g_return_if_fail(filter != NULL);
+  g_return_if_fail(filter->num_measures > measure);
+  g_return_if_fail(filter->total_beats > (filter->num_beats * measure + beat));
+
+  filter->times[measure] ^= (1 << beat);
+}
+
+static void
+play_on_demand_set_property (GObject *object, guint prop_id,
+                             const GValue *value, GParamSpec *pspec)
 {
   GstPlayOnDemand *filter;
+  register guchar  c;
+  register guint   i;
+  gchar           *new_buffer;
+  guint64         *new_measures;
 
   /* it's not null if we got it, but it might not be ours */
   g_return_if_fail(GST_IS_PLAYONDEMAND(object));
   filter = GST_PLAYONDEMAND(object);
+  g_return_if_fail(filter != NULL);
 
   switch (prop_id) {
-  case ARG_BUFFERSIZE:
+  case PROP_BUFFERSIZE:
     filter->buffer_size = g_value_get_uint(value);
 
-    /* reallocate space for the buffer with the new size values. */
+    if (filter->format == GST_PLAYONDEMAND_FORMAT_FLOAT) {
+      filter->buffer_samples = filter->buffer_size \
+        / sizeof(gfloat) / filter->channels;
+    } else {
+      filter->buffer_samples = filter->buffer_size \
+        / filter->width / filter->channels;
+    }
+
+    /* allocate space for a new buffer, copy old data, remove invalid play
+       pointers. */
+    new_buffer = g_new(gchar, filter->buffer_size);
+    for (c = 0; c < filter->buffer_size; c++) {
+      new_buffer[c] = filter->buffer[c];
+    }
+
     g_free(filter->buffer);
-    filter->buffer = g_new(gchar, filter->buffer_size);
+    filter->buffer = new_buffer;
 
-    /* reset the play pointers and read/write indexes. */
-    play_on_demand_reset_handler(GST_ELEMENT(filter));
+    for (i = 0; i < GST_POD_MAX_PLAY_PTRS; i++) {
+      if (filter->plays[i] > filter->buffer_size) {
+        filter->plays[i] = G_MAXUINT;
+      }
+    }
+    break;
+  case PROP_NUM_BEATS:
+    filter->num_beats = g_value_get_uint(value);
+    filter->total_beats = filter->num_measures * filter->num_beats;
     break;
-  case ARG_SILENT:
+  case PROP_NUM_MEASURES:
+    filter->num_measures = g_value_get_uint(value);
+    filter->total_beats = filter->num_measures * filter->num_beats;
+
+    /* reallocate space for beat information, copy old data. this will remove
+       measures at the end if the number of measures shrinks. */
+    new_measures = g_new(guint64, filter->num_measures);
+    for (i = 0; i < filter->num_measures; i++) {
+      new_measures[i] = filter->times[i];
+    }
+
+    g_free(filter->times);
+    filter->times = new_measures;
+    break;
+  case PROP_SILENT:
     filter->silent = g_value_get_boolean(value);
     break;
-  case ARG_FOLLOWTAIL:
-    filter->follow_stream_tail = g_value_get_boolean(value);
+  case PROP_PLAYFROMBEGINNING:
+    filter->play_from_beginning = g_value_get_boolean(value);
     play_on_demand_reset_handler(GST_ELEMENT(filter));
     break;
   default:
@@ -380,23 +583,25 @@ play_on_demand_set_property (GObject *object, guint prop_id, const GValue *value
 }
 
 static void
-play_on_demand_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec)
+play_on_demand_get_property (GObject *object, guint prop_id,
+                             GValue *value, GParamSpec *pspec)
 {
   GstPlayOnDemand *filter;
 
   /* it's not null if we got it, but it might not be ours */
   g_return_if_fail(GST_IS_PLAYONDEMAND(object));
   filter = GST_PLAYONDEMAND(object);
+  g_return_if_fail(filter != NULL);
 
   switch (prop_id) {
-  case ARG_BUFFERSIZE:
+  case PROP_BUFFERSIZE:
     g_value_set_uint(value, filter->buffer_size);
     break;
-  case ARG_SILENT:
+  case PROP_SILENT:
     g_value_set_boolean(value, filter->silent);
     break;
-  case ARG_FOLLOWTAIL:
-    g_value_set_boolean(value, filter->follow_stream_tail);
+  case PROP_PLAYFROMBEGINNING:
+    g_value_set_boolean(value, filter->play_from_beginning);
     break;
   default:
     G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
@@ -413,7 +618,7 @@ plugin_init (GModule *module, GstPlugin *plugin)
                                    GST_TYPE_PLAYONDEMAND,
                                    &play_on_demand_details);
   g_return_val_if_fail(factory != NULL, FALSE);
-  
+
   gst_element_factory_add_pad_template(factory, play_on_demand_src_factory());
   gst_element_factory_add_pad_template(factory, play_on_demand_sink_factory());
 
diff --git a/gst/playondemand/gstplayondemand.h b/gst/playondemand/gstplayondemand.h
index 57dd189d..d34c0c6f 100644
--- a/gst/playondemand/gstplayondemand.h
+++ b/gst/playondemand/gstplayondemand.h
@@ -25,7 +25,6 @@
 
 #include <config.h>
 #include <gst/gst.h>
-/* #include <gst/meta/audioraw.h> */
 
 
 #ifdef __cplusplus
@@ -65,30 +64,46 @@ struct _GstPlayOnDemand {
      size. */
   gchar    *buffer;
   guint     buffer_size;
+  guint     buffer_samples;
 
+  guint    *plays;
   guint     write;
   guint     start;
 
-  guint    *plays;
+  gboolean  play_from_beginning;
+  gboolean  buffer_filled_once;
 
   gboolean  eos;
-
-  gboolean  follow_stream_tail;
-  
   gboolean  silent;
-  
+
+  /* the playondemand filter needs to keep track of a number of 'measures'
+     consisting of 'beats'. these are represented as an array of guint64s, with
+     each guint64 being one measure, and the bits in each measure being beats
+     (lower order bits come first). each measure can therefore have a maximum of
+     64 beats, though there are a potentially unlimited number of measures.
+
+     this is basically a way to figure out when incoming clock signals should
+     add a play pointer. */
+  GstClock *clock;
+  guint     last_time;
+
+  guint64  *times;
+  guint     num_measures;
+  guint     num_beats;
+  guint     total_beats;
+
   /* the next three are valid for both int and float */
   GstPlayOnDemandFormat format;
   guint                 rate;
   guint                 channels;
-  
+
   /* the next five are valid only for format == GST_PLAYONDEMAND_FORMAT_INT */
   guint    width;
   guint    depth;
   guint    endianness;
   guint    law;
   gboolean is_signed;
-  
+
   /* the next three are valid only for format == GST_PLAYONDEMAND_FORMAT_FLOAT */
   const gchar *layout;
   gfloat       slope;
@@ -104,6 +119,17 @@ struct _GstPlayOnDemandClass {
 
 GType gst_play_on_demand_get_type(void);
 
+void gst_play_on_demand_set_beat     (GstPlayOnDemand *filter,
+                                      const guint measure,
+                                      const guint beat,
+                                      const gboolean value);
+gboolean gst_play_on_demand_get_beat (GstPlayOnDemand *filter,
+                                      const guint measure,
+                                      const guint beat);
+void gst_play_on_demand_toggle_beat  (GstPlayOnDemand *filter,
+                                      const guint measure,
+                                      const guint beat);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */