From af29e7785890c7881dd8664eff894664a4c8174e Mon Sep 17 00:00:00 2001
From: Stefan Sauer <ensonic@users.sf.net>
Date: Fri, 12 Feb 2016 20:57:29 +0100
Subject: [PATCH] monoscope: rework the scaling code

The running average was wrong and the resulting scaling factor was only held in
place using the CLAMP. In addtion we are now convering quickly to volume
changes.

FInally now with this change, we can change the resolution defines and
everythign adjusts.
---
 gst/monoscope/monoscope.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/gst/monoscope/monoscope.c b/gst/monoscope/monoscope.c
index 90c012ba24..3500879c1a 100644
--- a/gst/monoscope/monoscope.c
+++ b/gst/monoscope/monoscope.c
@@ -99,7 +99,7 @@ monoscope_update (struct monoscope_state *stateptr, gint16 data[convolver_big])
   int hh1 = hh - 1;
   guint32 *loc;
 
-  int factor;
+  double factor;
   int max = 1;
   short *thisEq = stateptr->copyEq;
 
@@ -108,21 +108,26 @@ monoscope_update (struct monoscope_state *stateptr, gint16 data[convolver_big])
 
   memset (stateptr->display, 0, scope_width * scope_height * sizeof (guint32));
   for (i = 0; i < convolver_small; i++) {
-    avg = thisEq[i] + (stateptr->avgEq[i] >> 1);
+    avg = (thisEq[i] + stateptr->avgEq[i]) >> 1;
     stateptr->avgEq[i] = avg;
     avg = abs (avg);
     max = MAX (max, avg);
   }
-  stateptr->avgMax += max - (stateptr->avgMax >> 8);
-  if (stateptr->avgMax < max)
-    stateptr->avgMax = max;     /* Avoid overflow */
-  factor = 0x7fffffff / stateptr->avgMax;
-  /* Keep the scaling sensible. */
-  factor = CLAMP (factor, (1 << 8), (1 << 18));
+  /* running average, 4 values is enough to make it follow volume changes
+   * if this value is too large it will converge slowly
+   */
+  stateptr->avgMax += (max / 4) - (stateptr->avgMax / 4);
+
+  /* input is +/- avgMax, output is +/- hh */
+  if (stateptr->avgMax) {
+    factor = (gdouble) hh / stateptr->avgMax;
+  } else {
+    factor = 1.0;
+  }
 
   for (i = 0; i < scope_width; i++) {
+    /* scale 16bit signed audio values to scope_height */
     foo = stateptr->avgEq[i] * factor;
-    foo >>= 18;
     foo = CLAMP (foo, -hh1, hh1);
     bar = (i + ((foo + hh) * scope_width));
     if ((bar > 0) && (bar < (scope_width * scope_height))) {