[gtk+] video-timer: add a test case for display at a constant frame rate

[Owen Taylor <otaylor src gnome org>]

commit e77a96a0ea3365d6e899b2058520f96cfddd0143
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Thu Nov 15 17:39:30 2012 -0500

    video-timer: add a test case for display at a constant frame rate
    
    Add a test case that simulates the timing operaton that goes on
    when showing a constant frame rate stream like a video - each
    frame is shown at the VBlank interval that is closest to when it
    would ideally be timed.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=685460

 tests/Makefile.am   |    7 +
 tests/video-timer.c |  328 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 335 insertions(+), 0 deletions(-)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index cf7499f..143f8e4 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -30,6 +30,7 @@ noinst_PROGRAMS =  $(TEST_PROGS)      \
        simple                          \
        flicker                         \
        print-editor                    \
+       video-timer                     \
        testaccel                       \
        testadjustsize                  \
        testappchooser                  \
@@ -156,6 +157,7 @@ flicker_DEPENDENCIES = $(TEST_DEPS)
 motion_compression_DEPENDENCIES = $(TEST_DEPS)
 simple_DEPENDENCIES = $(TEST_DEPS)
 print_editor_DEPENDENCIES = $(TEST_DEPS)
+video_timer_DEPENDENCIES = $(TEST_DEPS)
 testheightforwidth_DEPENDENCIES = $(TEST_DEPS)
 testicontheme_DEPENDENCIES = $(TEST_DEPS)
 testiconview_DEPENDENCIES = $(TEST_DEPS)
@@ -258,6 +260,11 @@ animated_resizing_SOURCES =        \
        variable.c              \
        variable.h
 
+video_timer_SOURCES =  \
+       video-timer.c   \
+       variable.c      \
+       variable.h
+
 testboxcss_SOURCES =   \
        testboxcss.c    \
        prop-editor.c
diff --git a/tests/video-timer.c b/tests/video-timer.c
new file mode 100644
index 0000000..ad73612
--- /dev/null
+++ b/tests/video-timer.c
@@ -0,0 +1,328 @@
+#include <math.h>
+#include <gtk/gtk.h>
+
+#include "variable.h"
+
+typedef struct {
+  gdouble angle;
+  gint64 stream_time;
+  gint64 clock_time;
+  gint64 frame_counter;
+} FrameData;
+
+static FrameData *displayed_frame;
+static GtkWidget *window;
+static GList *past_frames;
+static Variable latency_error = VARIABLE_INIT;
+static int dropped_frames = 0;
+static int n_frames = 0;
+
+static int fps = 24;
+
+/* Thread-safe frame queue */
+
+#define MAX_QUEUE_LENGTH 5
+
+static GQueue *frame_queue;
+static GMutex frame_mutex;
+static GCond frame_cond;
+
+static void
+queue_frame (FrameData *frame_data)
+{
+  g_mutex_lock (&frame_mutex);
+
+  while (frame_queue->length == MAX_QUEUE_LENGTH)
+    g_cond_wait (&frame_cond, &frame_mutex);
+
+  g_queue_push_tail (frame_queue, frame_data);
+
+  g_mutex_unlock (&frame_mutex);
+}
+
+static FrameData *
+unqueue_frame (void)
+{
+  FrameData *frame_data;
+
+  g_mutex_lock (&frame_mutex);
+
+  if (frame_queue->length > 0)
+    {
+      frame_data = g_queue_pop_head (frame_queue);
+      g_cond_signal (&frame_cond);
+    }
+  else
+    {
+      frame_data = NULL;
+    }
+
+  g_mutex_unlock (&frame_mutex);
+
+  return frame_data;
+}
+
+static FrameData *
+peek_pending_frame (void)
+{
+  FrameData *frame_data;
+
+  g_mutex_lock (&frame_mutex);
+
+  if (frame_queue->head)
+    frame_data = frame_queue->head->data;
+  else
+    frame_data = NULL;
+
+  g_mutex_unlock (&frame_mutex);
+
+  return frame_data;
+}
+
+static FrameData *
+peek_next_frame (void)
+{
+  FrameData *frame_data;
+
+  g_mutex_lock (&frame_mutex);
+
+  if (frame_queue->head && frame_queue->head->next)
+    frame_data = frame_queue->head->next->data;
+  else
+    frame_data = NULL;
+
+  g_mutex_unlock (&frame_mutex);
+
+  return frame_data;
+}
+
+/* Frame producer thread */
+
+static gpointer
+create_frames_thread (gpointer data)
+{
+  int frame_count = 0;
+
+  while (TRUE)
+    {
+      FrameData *frame_data = g_slice_new0 (FrameData);
+      frame_data->angle = 2 * M_PI * (frame_count % fps) / (double)fps;
+      frame_data->stream_time = (G_GINT64_CONSTANT (1000000) * frame_count) / fps;
+
+      queue_frame (frame_data);
+      frame_count++;
+    }
+
+  return NULL;
+}
+
+/* Clock management */
+
+#define PRE_BUFFER_TIME 500000
+
+static gint64 start_time;
+
+static gint64
+stream_time_to_clock_time (gint64 stream_time)
+{
+  return start_time + stream_time + PRE_BUFFER_TIME;
+}
+
+/* Drawing */
+
+static void
+on_window_draw (GtkWidget *widget,
+                cairo_t   *cr)
+{
+  GdkRectangle allocation;
+  double cx, cy, r;
+
+  cairo_set_source_rgb (cr, 1., 1., 1.);
+  cairo_paint (cr);
+
+  cairo_set_source_rgb (cr, 0., 0., 0.);
+  gtk_widget_get_allocation (widget, &allocation);
+
+  cx = allocation.width / 2.;
+  cy = allocation.height / 2.;
+  r = MIN (allocation.width, allocation.height) / 2.;
+
+  cairo_arc (cr, cx, cy, r,
+             0, 2 * M_PI);
+  cairo_stroke (cr);
+  if (displayed_frame)
+    {
+      cairo_move_to (cr, cx, cy);
+      cairo_line_to (cr,
+                     cx + r * cos(displayed_frame->angle - M_PI / 2),
+                     cy + r * sin(displayed_frame->angle - M_PI / 2));
+      cairo_stroke (cr);
+
+      if (displayed_frame->frame_counter == 0)
+        {
+          GdkFrameClock *frame_clock = gtk_widget_get_frame_clock (window);
+          GdkFrameHistory *history = gdk_frame_clock_get_history (frame_clock);
+
+          displayed_frame->frame_counter = gdk_frame_history_get_frame_counter (history);
+        }
+    }
+}
+
+static void
+collect_old_frames (void)
+{
+  GdkFrameClock *frame_clock = gtk_widget_get_frame_clock (window);
+  GdkFrameHistory *history = gdk_frame_clock_get_history (frame_clock);
+  GList *l, *l_next;
+
+  for (l = past_frames; l; l = l_next)
+    {
+      FrameData *frame_data = l->data;
+      gboolean remove = FALSE;
+      l_next = l->next;
+
+      GdkFrameTimings *timings = gdk_frame_history_get_timings (history,
+                                                                frame_data->frame_counter);
+      if (timings == NULL)
+        {
+          remove = TRUE;
+        }
+      else if (gdk_frame_timings_get_complete (timings))
+        {
+          gint64 presentation_time = gdk_frame_timings_get_presentation_time (timings);
+          if (presentation_time)
+            variable_add (&latency_error,
+                          presentation_time - frame_data->clock_time);
+
+          remove = TRUE;
+        }
+
+      if (remove)
+        {
+          past_frames = g_list_delete_link (past_frames, l);
+          g_slice_free (FrameData, frame_data);
+        }
+    }
+}
+
+static void
+print_statistics (void)
+{
+  gint64 now = g_get_monotonic_time ();
+  static gint64 last_print_time = 0;
+
+  if (last_print_time == 0)
+    last_print_time = now;
+  else if (now -last_print_time > 5000000)
+    {
+      g_print ("dropped_frames: %d/%d\n",
+               dropped_frames, n_frames);
+      g_print ("collected_frames: %g/%d\n",
+               latency_error.weight, n_frames);
+      g_print ("latency_error: %g +/- %g\n",
+               variable_mean (&latency_error),
+               variable_standard_deviation (&latency_error));
+      variable_reset (&latency_error);
+      dropped_frames = 0;
+      n_frames = 0;
+      last_print_time = now;
+    }
+}
+
+static void
+on_update (GdkFrameClock *frame_clock,
+           gpointer       data)
+{
+  GdkFrameTimings *timings = gdk_frame_clock_get_current_frame_timings (frame_clock);
+  gint64 frame_time = gdk_frame_timings_get_frame_time (timings);
+  gint64 predicted_presentation_time = gdk_frame_timings_get_predicted_presentation_time (timings);
+  gint64 refresh_interval;
+  FrameData *pending_frame;
+
+  if (start_time == 0)
+    start_time = frame_time;
+
+  gdk_frame_clock_get_refresh_info (frame_clock, frame_time,
+                                    &refresh_interval, NULL);
+
+  pending_frame = peek_pending_frame ();
+  if (stream_time_to_clock_time (pending_frame->stream_time)
+      < predicted_presentation_time + refresh_interval / 2)
+    {
+      while (TRUE)
+        {
+          FrameData *next_frame = peek_next_frame ();
+          if (next_frame &&
+              stream_time_to_clock_time (next_frame->stream_time)
+              < predicted_presentation_time + refresh_interval / 2)
+            {
+              g_slice_free (FrameData, unqueue_frame ());
+              n_frames++;
+              dropped_frames++;
+              pending_frame = next_frame;
+            }
+          else
+            break;
+        }
+
+      if (displayed_frame)
+        past_frames = g_list_prepend (past_frames, displayed_frame);
+
+      n_frames++;
+      displayed_frame = unqueue_frame ();
+      displayed_frame->clock_time = stream_time_to_clock_time (displayed_frame->stream_time);
+      displayed_frame->frame_counter = gdk_frame_timings_get_frame_counter (timings);
+
+      collect_old_frames ();
+      print_statistics ();
+
+      gtk_widget_queue_draw (window);
+    }
+
+  gdk_frame_clock_request_phase (frame_clock, GDK_FRAME_CLOCK_PHASE_UPDATE);
+}
+
+static GOptionEntry options[] = {
+  { "fps", 'f', 0, G_OPTION_ARG_INT, &fps, "Frame rate", "FPS" },
+  { NULL }
+};
+
+int
+main(int argc, char **argv)
+{
+  GError *error = NULL;
+  GdkFrameClock *frame_clock;
+
+  if (!gtk_init_with_args (&argc, &argv, "",
+                           options, NULL, &error))
+    {
+      g_printerr ("Option parsing failed: %s\n", error->message);
+      return 1;
+    }
+
+  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_widget_set_app_paintable (window, TRUE);
+  gtk_window_set_default_size (GTK_WINDOW (window), 300, 300);
+
+  g_signal_connect (window, "draw",
+                    G_CALLBACK (on_window_draw), NULL);
+  g_signal_connect (window, "destroy",
+                    G_CALLBACK (gtk_main_quit), NULL);
+
+  gtk_widget_show (window);
+
+  frame_queue = g_queue_new ();
+  g_mutex_init (&frame_mutex);
+  g_cond_init (&frame_cond);
+
+  g_thread_new ("Create Frames", create_frames_thread, NULL);
+
+  frame_clock = gtk_widget_get_frame_clock (window);
+  g_signal_connect (frame_clock, "update",
+                    G_CALLBACK (on_update), NULL);
+  gdk_frame_clock_request_phase (frame_clock, GDK_FRAME_CLOCK_PHASE_UPDATE);
+
+  gtk_main ();
+
+  return 0;
+}