forked from AuroraMiddleware/gtk
1db87c897f
Add an API to start or stop continually updating the frame clock. This is a slight convenience for applcations and avoids the problem of getting one more frame run after an animation stops, but the primary motivation for this is because it looks like we might have to use timeBeginPeriod()/timeEndPeriod() on Windows to get reasonably accurate timing, and for that we'll need to know if there is an animation running. https://bugzilla.gnome.org/show_bug.cgi?id=693934
400 lines
11 KiB
C
400 lines
11 KiB
C
#include <math.h>
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#include <gtk/gtk.h>
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#include "variable.h"
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typedef struct {
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gdouble angle;
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gint64 stream_time;
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gint64 clock_time;
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gint64 frame_counter;
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} FrameData;
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static FrameData *displayed_frame;
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static GtkWidget *window;
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static GList *past_frames;
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static Variable latency_error = VARIABLE_INIT;
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static Variable time_factor_stats = VARIABLE_INIT;
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static int dropped_frames = 0;
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static int n_frames = 0;
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static gboolean pll;
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static int fps = 24;
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/* Thread-safe frame queue */
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#define MAX_QUEUE_LENGTH 5
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static GQueue *frame_queue;
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static GMutex frame_mutex;
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static GCond frame_cond;
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static void
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queue_frame (FrameData *frame_data)
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{
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g_mutex_lock (&frame_mutex);
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while (frame_queue->length == MAX_QUEUE_LENGTH)
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g_cond_wait (&frame_cond, &frame_mutex);
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g_queue_push_tail (frame_queue, frame_data);
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g_mutex_unlock (&frame_mutex);
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}
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static FrameData *
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unqueue_frame (void)
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{
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FrameData *frame_data;
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g_mutex_lock (&frame_mutex);
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if (frame_queue->length > 0)
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{
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frame_data = g_queue_pop_head (frame_queue);
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g_cond_signal (&frame_cond);
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}
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else
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{
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frame_data = NULL;
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}
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g_mutex_unlock (&frame_mutex);
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return frame_data;
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}
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static FrameData *
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peek_pending_frame (void)
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{
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FrameData *frame_data;
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g_mutex_lock (&frame_mutex);
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if (frame_queue->head)
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frame_data = frame_queue->head->data;
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else
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frame_data = NULL;
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g_mutex_unlock (&frame_mutex);
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return frame_data;
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}
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static FrameData *
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peek_next_frame (void)
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{
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FrameData *frame_data;
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g_mutex_lock (&frame_mutex);
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if (frame_queue->head && frame_queue->head->next)
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frame_data = frame_queue->head->next->data;
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else
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frame_data = NULL;
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g_mutex_unlock (&frame_mutex);
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return frame_data;
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}
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/* Frame producer thread */
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static gpointer
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create_frames_thread (gpointer data)
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{
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int frame_count = 0;
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while (TRUE)
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{
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FrameData *frame_data = g_slice_new0 (FrameData);
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frame_data->angle = 2 * M_PI * (frame_count % fps) / (double)fps;
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frame_data->stream_time = (G_GINT64_CONSTANT (1000000) * frame_count) / fps;
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queue_frame (frame_data);
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frame_count++;
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}
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return NULL;
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}
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/* Clock management:
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*
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* The logic here, which is activated by the --pll argument
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* demonstrates adjusting the playback rate so that the frames exactly match
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* when they are displayed both frequency and phase. If there was an
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* accompanying audio track, you would need to resample the audio to match
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* the clock.
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*
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* The algorithm isn't exactly a PLL - I wrote it first that way, but
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* it oscillicated before coming into sync and this approach was easier than
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* fine-tuning the PLL filter.
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*
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* A more complicated algorithm could also establish sync when the playback
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* rate isn't exactly an integral divisor of the VBlank rate, such as 24fps
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* video on a 60fps display.
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*/
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#define PRE_BUFFER_TIME 500000
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static gint64 stream_time_base;
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static gint64 clock_time_base;
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static double time_factor = 1.0;
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static double frequency_time_factor = 1.0;
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static double phase_time_factor = 1.0;
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static gint64
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stream_time_to_clock_time (gint64 stream_time)
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{
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return clock_time_base + (stream_time - stream_time_base) * time_factor;
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}
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static void
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adjust_clock_for_phase (gint64 frame_clock_time,
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gint64 presentation_time)
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{
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static gint count = 0;
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static gint64 previous_frame_clock_time;
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static gint64 previous_presentation_time;
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gint64 phase = presentation_time - frame_clock_time;
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count++;
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if (count >= fps) /* Give a second of warmup */
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{
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gint64 time_delta = frame_clock_time - previous_frame_clock_time;
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gint64 previous_phase = previous_presentation_time - previous_frame_clock_time;
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double expected_phase_delta;
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stream_time_base += (frame_clock_time - clock_time_base) / time_factor;
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clock_time_base = frame_clock_time;
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expected_phase_delta = time_delta * (1 - phase_time_factor);
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/* If the phase is increasing that means the computed clock times are
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* increasing too slowly. We increase the frequency time factor to compensate,
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* but decrease the compensation so that it takes effect over 1 second to
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* avoid jitter */
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frequency_time_factor += (phase - previous_phase - expected_phase_delta) / (double)time_delta / fps;
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/* We also want to increase or decrease the frequency to bring the phase
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* into sync. We do that again so that the phase should sync up over 1 seconds
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*/
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phase_time_factor = 1 + phase / 2000000.;
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time_factor = frequency_time_factor * phase_time_factor;
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}
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previous_frame_clock_time = frame_clock_time;
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previous_presentation_time = presentation_time;
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}
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/* Drawing */
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static void
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on_window_draw (GtkWidget *widget,
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cairo_t *cr)
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{
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GdkRectangle allocation;
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double cx, cy, r;
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cairo_set_source_rgb (cr, 1., 1., 1.);
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cairo_paint (cr);
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cairo_set_source_rgb (cr, 0., 0., 0.);
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gtk_widget_get_allocation (widget, &allocation);
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cx = allocation.width / 2.;
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cy = allocation.height / 2.;
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r = MIN (allocation.width, allocation.height) / 2.;
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cairo_arc (cr, cx, cy, r,
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0, 2 * M_PI);
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cairo_stroke (cr);
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if (displayed_frame)
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{
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cairo_move_to (cr, cx, cy);
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cairo_line_to (cr,
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cx + r * cos(displayed_frame->angle - M_PI / 2),
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cy + r * sin(displayed_frame->angle - M_PI / 2));
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cairo_stroke (cr);
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if (displayed_frame->frame_counter == 0)
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{
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GdkFrameClock *frame_clock = gtk_widget_get_frame_clock (window);
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displayed_frame->frame_counter = gdk_frame_clock_get_frame_counter (frame_clock);
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}
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}
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}
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static void
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collect_old_frames (void)
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{
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GdkFrameClock *frame_clock = gtk_widget_get_frame_clock (window);
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GList *l, *l_next;
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for (l = past_frames; l; l = l_next)
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{
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FrameData *frame_data = l->data;
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gboolean remove = FALSE;
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l_next = l->next;
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GdkFrameTimings *timings = gdk_frame_clock_get_timings (frame_clock,
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frame_data->frame_counter);
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if (timings == NULL)
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{
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remove = TRUE;
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}
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else if (gdk_frame_timings_get_complete (timings))
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{
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gint64 presentation_time = gdk_frame_timings_get_predicted_presentation_time (timings);
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gint64 refresh_interval = gdk_frame_timings_get_refresh_interval (timings);
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if (pll &&
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presentation_time && refresh_interval &&
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presentation_time > frame_data->clock_time - refresh_interval / 2 &&
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presentation_time < frame_data->clock_time + refresh_interval / 2)
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adjust_clock_for_phase (frame_data->clock_time, presentation_time);
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if (presentation_time)
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variable_add (&latency_error,
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presentation_time - frame_data->clock_time);
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remove = TRUE;
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}
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if (remove)
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{
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past_frames = g_list_delete_link (past_frames, l);
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g_slice_free (FrameData, frame_data);
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}
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}
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}
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static void
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print_statistics (void)
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{
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gint64 now = g_get_monotonic_time ();
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static gint64 last_print_time = 0;
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if (last_print_time == 0)
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last_print_time = now;
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else if (now -last_print_time > 5000000)
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{
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g_print ("dropped_frames: %d/%d\n",
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dropped_frames, n_frames);
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g_print ("collected_frames: %g/%d\n",
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latency_error.weight, n_frames);
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g_print ("latency_error: %g +/- %g\n",
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variable_mean (&latency_error),
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variable_standard_deviation (&latency_error));
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if (pll)
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g_print ("playback rate adjustment: %g +/- %g %%\n",
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(variable_mean (&time_factor_stats) - 1) * 100,
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variable_standard_deviation (&time_factor_stats) * 100);
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variable_reset (&latency_error);
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variable_reset (&time_factor_stats);
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dropped_frames = 0;
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n_frames = 0;
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last_print_time = now;
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}
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}
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static void
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on_update (GdkFrameClock *frame_clock,
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gpointer data)
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{
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GdkFrameTimings *timings = gdk_frame_clock_get_current_timings (frame_clock);
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gint64 frame_time = gdk_frame_timings_get_frame_time (timings);
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gint64 predicted_presentation_time = gdk_frame_timings_get_predicted_presentation_time (timings);
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gint64 refresh_interval;
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FrameData *pending_frame;
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if (clock_time_base == 0)
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clock_time_base = frame_time + PRE_BUFFER_TIME;
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gdk_frame_clock_get_refresh_info (frame_clock, frame_time,
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&refresh_interval, NULL);
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pending_frame = peek_pending_frame ();
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if (stream_time_to_clock_time (pending_frame->stream_time)
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< predicted_presentation_time + refresh_interval / 2)
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{
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while (TRUE)
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{
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FrameData *next_frame = peek_next_frame ();
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if (next_frame &&
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stream_time_to_clock_time (next_frame->stream_time)
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< predicted_presentation_time + refresh_interval / 2)
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{
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g_slice_free (FrameData, unqueue_frame ());
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n_frames++;
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dropped_frames++;
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pending_frame = next_frame;
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}
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else
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break;
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}
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if (displayed_frame)
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past_frames = g_list_prepend (past_frames, displayed_frame);
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n_frames++;
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displayed_frame = unqueue_frame ();
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displayed_frame->clock_time = stream_time_to_clock_time (displayed_frame->stream_time);
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displayed_frame->frame_counter = gdk_frame_timings_get_frame_counter (timings);
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variable_add (&time_factor_stats, time_factor);
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collect_old_frames ();
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print_statistics ();
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gtk_widget_queue_draw (window);
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}
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}
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static GOptionEntry options[] = {
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{ "pll", 'p', 0, G_OPTION_ARG_NONE, &pll, "Sync frame rate to refresh", NULL },
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{ "fps", 'f', 0, G_OPTION_ARG_INT, &fps, "Frame rate", "FPS" },
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{ NULL }
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};
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int
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main(int argc, char **argv)
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{
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GError *error = NULL;
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GdkFrameClock *frame_clock;
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if (!gtk_init_with_args (&argc, &argv, "",
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options, NULL, &error))
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{
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g_printerr ("Option parsing failed: %s\n", error->message);
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return 1;
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}
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window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
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gtk_widget_set_app_paintable (window, TRUE);
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gtk_window_set_default_size (GTK_WINDOW (window), 300, 300);
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g_signal_connect (window, "draw",
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G_CALLBACK (on_window_draw), NULL);
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g_signal_connect (window, "destroy",
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G_CALLBACK (gtk_main_quit), NULL);
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gtk_widget_show (window);
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frame_queue = g_queue_new ();
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g_mutex_init (&frame_mutex);
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g_cond_init (&frame_cond);
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g_thread_new ("Create Frames", create_frames_thread, NULL);
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frame_clock = gtk_widget_get_frame_clock (window);
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g_signal_connect (frame_clock, "update",
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G_CALLBACK (on_update), NULL);
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gdk_frame_clock_begin_updating (frame_clock);
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gtk_main ();
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return 0;
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}
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