Merge remote-tracking branch 'qatar/master'

[ffmpeg] / libavdevice / timefilter.c

diff --git a/libavdevice/timefilter.c b/libavdevice/timefilter.c
index ff6552f7d773919bfe571172da5f09c3be97fb1f..a423fc08592f8e92bbc378cae214fd680048b129 100644 (file)
--- a/libavdevice/timefilter.c
+++ b/libavdevice/timefilter.c
@@ -36,14 +36,21 @@ struct TimeFilter {
     int count;
 };
 
-TimeFilter *ff_timefilter_new(double clock_period,
-                              double feedback2_factor,
-                              double feedback3_factor)
+/* 1 - exp(-x) using a 3-order power series */
+static double qexpneg(double x)
+{
+    return 1 - 1 / (1 + x * (1 + x / 2 * (1 + x / 3)));
+}
+
+TimeFilter *ff_timefilter_new(double time_base,
+                              double period,
+                              double bandwidth)
 {
     TimeFilter *self       = av_mallocz(sizeof(TimeFilter));
-    self->clock_period     = clock_period;
-    self->feedback2_factor = feedback2_factor;
-    self->feedback3_factor = feedback3_factor;
+    double o               = 2 * M_PI * bandwidth * period * time_base;
+    self->clock_period     = time_base;
+    self->feedback2_factor = qexpneg(M_SQRT2 * o);
+    self->feedback3_factor = qexpneg(o * o) / period;
     return self;
 }
 
@@ -71,11 +78,16 @@ double ff_timefilter_update(TimeFilter *self, double system_time, double period)
 
         /// update loop
         self->cycle_time   += FFMAX(self->feedback2_factor, 1.0 / self->count) * loop_error;
-        self->clock_period += self->feedback3_factor * loop_error / period;
+        self->clock_period += self->feedback3_factor * loop_error;
     }
     return self->cycle_time;
 }
 
+double ff_timefilter_eval(TimeFilter *self, double delta)
+{
+    return self->cycle_time + self->clock_period * delta;
+}
+
 #ifdef TEST
 #include "libavutil/lfg.h"
 #define LFG_MAX ((1LL << 32) - 1)
@@ -89,6 +101,7 @@ int main(void)
 #define SAMPLES 1000
     double ideal[SAMPLES];
     double samples[SAMPLES];
+    double samplet[SAMPLES];
 #if 1
     for (n0 = 0; n0 < 40; n0 = 2 * n0 + 1) {
         for (n1 = 0; n1 < 10; n1 = 2 * n1 + 1) {
@@ -100,13 +113,16 @@ int main(void)
 #endif
             double best_error = 1000000000;
             double bestpar0   = 1;
-            double bestpar1   = 0.001;
+            double bestpar1   = 1;
             int better, i;
 
             av_lfg_init(&prng, 123);
             for (i = 0; i < SAMPLES; i++) {
-                ideal[i]   = 10 + i + n1 * i / (1000);
+                samplet[i] = 10 + i + (av_lfg_get(&prng) < LFG_MAX/2 ? 0 : 0.999);
+                ideal[i]   = samplet[i] + n1 * i / (1000);
                 samples[i] = ideal[i] + n0 * (av_lfg_get(&prng) - LFG_MAX / 2) / (LFG_MAX * 10LL);
+                if(i && samples[i]<samples[i-1])
+                    samples[i]=samples[i-1]+0.001;
             }
 
             do {
@@ -118,7 +134,9 @@ int main(void)
                         TimeFilter *tf = ff_timefilter_new(1, par0, par1);
                         for (i = 0; i < SAMPLES; i++) {
                             double filtered;
-                            filtered = ff_timefilter_update(tf, samples[i], 1);
+                            filtered = ff_timefilter_update(tf, samples[i], i ? (samplet[i] - samplet[i-1]) : 1);
+                            if(filtered < 0 || filtered > 1000000000)
+                                printf("filter is unstable\n");
                             error   += (filtered - ideal[i]) * (filtered - ideal[i]);
                         }
                         ff_timefilter_destroy(tf);