Android: Change camera fps range selection

webrtc/api/java/android/org/webrtc/CameraEnumerationAndroid.java

Index: webrtc/api/java/android/org/webrtc/CameraEnumerationAndroid.java
diff --git a/webrtc/api/java/android/org/webrtc/CameraEnumerationAndroid.java b/webrtc/api/java/android/org/webrtc/CameraEnumerationAndroid.java
index 2fa685d1fbceda2fbb9f7ceac4d2e2bb5bfdb251..87b9a40b628703369f4949aa2abc1bb0043423cd 100644
--- a/webrtc/api/java/android/org/webrtc/CameraEnumerationAndroid.java
+++ b/webrtc/api/java/android/org/webrtc/CameraEnumerationAndroid.java
@@ -181,15 +181,37 @@ public class CameraEnumerationAndroid {
     }
   }
 
+  // Prefer a fps range with an upper bound close to |framerate|. Also prefer a fps range with a low
+  // lower bound, to allow the framerate to fluctuate based on lightning conditions.
   public static CaptureFormat.FramerateRange getClosestSupportedFramerateRange(
       List<CaptureFormat.FramerateRange> supportedFramerates, final int requestedFps) {
     return Collections.min(supportedFramerates,
         new ClosestComparator<CaptureFormat.FramerateRange>() {
-          private static final int MAX_FPS_WEIGHT = 10;
+          // Progressive penalty if the upper bound is further away than |MAX_FPS_DIFF_THRESHOLD|
+          // from requested.
+          private static final int MAX_FPS_DIFF_THRESHOLD = 5000;
+          private static final int MAX_FPS_LOW_DIFF_WEIGHT = 1;
+          private static final int MAX_FPS_HIGH_DIFF_WEIGHT = 3;
+
+          // Progressive penalty if the lower bound is bigger than |MIN_FPS_THRESHOLD|.
+          private static final int MIN_FPS_THRESHOLD = 8000;
+          private static final int MIN_FPS_LOW_VALUE_WEIGHT = 1;
+          private static final int MIN_FPS_HIGH_VALUE_WEIGHT = 4;
+
+          // Use one weight for small |value| less than |threshold|, and another weight above.
+          private int progressivePenalty(int value, int threshold, int lowWeight, int highWeight) {
+            return (value < threshold)
+                ? value * lowWeight
+                : threshold * lowWeight + (value - threshold) * highWeight;
+          }
 
           @Override
           int diff(CaptureFormat.FramerateRange range) {
-            return range.min + MAX_FPS_WEIGHT * abs(requestedFps * 1000 - range.max);
+            final int minFpsError = progressivePenalty(range.min,
+                MIN_FPS_THRESHOLD, MIN_FPS_LOW_VALUE_WEIGHT, MIN_FPS_HIGH_VALUE_WEIGHT);
+            final int maxFpsError = progressivePenalty(Math.abs(requestedFps * 1000 - range.max),
+                MAX_FPS_DIFF_THRESHOLD, MAX_FPS_LOW_DIFF_WEIGHT, MAX_FPS_HIGH_DIFF_WEIGHT);
+            return minFpsError + maxFpsError;
           }
      });
   }