Timefilter code by Olivier Guilyardi o list O samalyse o com

Originally committed as revision 17838 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/timefilter.c

@@ -0,0 +1,77 @@
+/*
+ * Delay Locked Loop based time filter
+ * Copyright (c) 2009 Samalyse
+ * Author: Olivier Guilyardi <olivier samalyse com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+
+#include "config.h"
+#include "avformat.h"
+#include "timefilter.h"
+
+struct TimeFilter {
+    /// Delay Locked Loop data. These variables refer to mathematical
+    /// concepts described in: http://www.kokkinizita.net/papers/usingdll.pdf
+    double cycle_time;
+    double next_cycle_time;
+    double feedback2_factor;
+    double feedback3_factor;
+    double integrator2_state;
+};
+
+TimeFilter * ff_timefilter_new(double period, double feedback2_factor, double feedback3_factor)
+{
+    TimeFilter *self        = av_mallocz(sizeof(TimeFilter));
+    self->integrator2_state = period;
+    self->feedback2_factor  = feedback2_factor;
+    self->feedback3_factor  = feedback3_factor;
+    return self;
+}
+
+void ff_timefilter_destroy(TimeFilter *self)
+{
+    av_freep(&self);
+}
+
+void ff_timefilter_reset(TimeFilter *self)
+{
+    self->cycle_time = 0;
+}
+
+void ff_timefilter_update(TimeFilter *self, double system_time)
+{
+    if (!self->cycle_time) {
+        /// init loop
+        self->cycle_time        = system_time;
+        self->next_cycle_time   = self->cycle_time + self->integrator2_state;
+    } else {
+        /// calculate loop error
+        double loop_error = system_time - self->next_cycle_time;
+
+        /// update loop
+        self->cycle_time         = self->next_cycle_time;
+        self->next_cycle_time   += self->feedback2_factor * loop_error + self->integrator2_state;
+        self->integrator2_state += self->feedback3_factor * loop_error;
+    }
+}
+
+double ff_timefilter_read(TimeFilter *self)
+{
+    return self->cycle_time;
+}