mixer: Implement non-linear time scale for fading.

[paraslash.git] / mixer.c

diff --git a/mixer.c b/mixer.c
index 6d1b5f5cad2d344c3f1eb6b2b441e7ef62e5d79c..d33fa831c9c3ba2cdc29c1ab3609795ab49bba16 100644 (file)
--- a/mixer.c
+++ b/mixer.c
@@ -8,6 +8,7 @@
 
 #include <regex.h>
 #include <lopsub.h>
+#include <math.h>
 
 #include "mixer.lsg.h"
 #include "para.h"
@@ -66,47 +67,87 @@ static int set_channel(struct mixer *m, struct mixer_handle *h, const char *chan
        return m->set_channel(h, channel);
 }
 
+static void millisleep(int ms)
+{
+       struct timespec ts;
+
+       PARA_INFO_LOG("sleeping %dms\n", ms);
+       if (ms < 0)
+               return;
+       ts.tv_sec = ms / 1000,
+       ts.tv_nsec = (ms % 1000) * 1000 * 1000;
+       nanosleep(&ts, NULL);
+}
+
+/*
+ * This implements the inverse function of t -> t^alpha, scaled to the time
+ * interval [0,T] and the range given by old_vol and new_vol. It returns the
+ * amount of milliseconds until the given volume is reached.
+ */
+static unsigned volume_time(double vol, double old_vol, double new_vol,
+               double T, double alpha)
+{
+       double c, d, x;
+
+       if (old_vol < new_vol) {
+               c = old_vol;
+               d = new_vol;
+       } else {
+               c = new_vol;
+               d = old_vol;
+       }
+
+       x = T * exp(log(((vol - c) / (d - c))) / alpha);
+       assert(x <= T);
+       if (old_vol < new_vol)
+               return x;
+       else
+               return T - x;
+}
+
 /* Fade to new volume in fade_time seconds. */
 static int fade(struct mixer *m, struct mixer_handle *h, uint32_t new_vol,
                uint32_t fade_time)
 {
-       int vol, diff, incr, ret;
-       unsigned secs;
-       struct timespec ts;
-       unsigned long long tmp, tmp2; /* Careful with that axe, Eugene! */
+       int i, T, old_vol, ret, slept, incr;
+       double ms, alpha;
+       uint32_t fe = OPT_UINT32_VAL(PARA_MIXER, FADE_EXPONENT);
 
-       if (fade_time <= 0)
-               return m->set(h, new_vol);
-       secs = fade_time;
+       if (fade_time <= 0 || fe >= 100) {
+               ret = m->set(h, new_vol);
+               if (ret < 0)
+                       return ret;
+               goto sleep;
+       }
+       alpha = (100 - fe) / 100.0;
        ret = m->get(h);
        if (ret < 0)
-               goto out;
-       vol = ret;
+               return ret;
+       old_vol = ret;
+       if (old_vol == new_vol)
+               goto sleep;
        PARA_NOTICE_LOG("fading %s from %d to %u in %u seconds\n",
-               OPT_STRING_VAL(PARA_MIXER, MIXER_CHANNEL), vol, new_vol, secs);
-       diff = new_vol - vol;
-       if (!diff) {
-               sleep(secs);
-               goto out;
-       }
-       incr = diff > 0? 1: -1;
-       diff = diff > 0? diff: -diff;
-       tmp = secs * 1000 / diff;
-       tmp2 = tmp % 1000;
-       while ((new_vol - vol) * incr > 0) {
-               ts.tv_nsec = tmp2 * 1000000; /* really nec ?*/
-               ts.tv_sec = tmp / 1000; /* really nec ?*/
-               //printf("ts.tv_sec: %i\n", ts.tv_nsec);
-               vol += incr;
-               ret = m->set(h, vol);
+               OPT_STRING_VAL(PARA_MIXER, MIXER_CHANNEL), old_vol,
+               new_vol, fade_time);
+       incr = old_vol < new_vol? 1 : -1;
+       T = fade_time * 1000;
+       i = old_vol;
+       slept = 0;
+       do {
+               ms = volume_time(i + incr, old_vol, new_vol, T, alpha);
+               millisleep(ms - slept);
+               slept = ms;
+               i += incr;
+               ret = m->set(h, i);
                if (ret < 0)
-                       goto out;
-               //printf("vol = %i\n", vol);
-               nanosleep(&ts, NULL);
-       }
-out:
+                       return ret;
+       } while (i != new_vol);
+       return 1;
+sleep:
+       sleep(fade_time);
        return ret;
 }
+
 static int com_fade(struct mixer *m, struct mixer_handle *h)
 {
        uint32_t new_vol = OPT_UINT32_VAL(FADE, FADE_VOL);