Update calcPeriodNsClusters

Author: azaat

app/src/main/java/com/googleresearch/capturesync/softwaresync/phasealign/PeriodCalculator.java

@@ -0,0 +1,83 @@
+package com.googleresearch.capturesync.softwaresync.phasealign;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class PeriodCalculator {
+    private final static long CALC_DURATION_MS = 5000;
+    private volatile boolean shouldRegister;
+    private ArrayList<Long> registeredTimestamps;
+
+    public PeriodCalculator() {
+        registeredTimestamps = new ArrayList<>();
+    }
+
+    // Blocking call, returns 0 in case of error
+    public long getPeriodNs() throws InterruptedException {
+        // Start recording timestamps
+        registeredTimestamps = new ArrayList<>();
+        shouldRegister = true;
+        Thread.sleep(CALC_DURATION_MS);
+        // Stop recording timestamps and calculate period
+        shouldRegister = false;
+        // TODO: switch to clusters!
+        return calcPeriodNsClusters(getDiff(registeredTimestamps));
+    }
+
+    private ArrayList<Long> getDiff(ArrayList<Long> arrayList) {
+        Long prev = 0L;
+        ArrayList<Long> result = new ArrayList<>();
+        for (Long aLong : arrayList) {
+            if (prev == 0L) {
+                prev = aLong;
+            } else {
+                result.add(aLong - prev);
+                prev = aLong;
+            }
+        }
+        return result;
+    }
+
+    private long calcPeriodNsClusters(ArrayList<Long> numArray) {
+        long initEstimate = Collections.min(numArray);
+        long nClust = Math.round(1.0 * Collections.max(numArray) / initEstimate);
+        double weightedSum = 0L;
+        for (int i = 0; i < nClust; i++) {
+            int finalI = i;
+            ArrayList<Long> clust = (ArrayList<Long>)numArray.stream().filter(
+                    x -> (x > (finalI + 0.5)*initEstimate) && (x < (finalI + 1.5)*initEstimate)
+            ).collect(Collectors.toList());
+            if (clust.size() > 0) {
+                weightedSum += 1.0 * median(clust) / (i + 1) * clust.size();
+            }
+        }
+        return Math.round(weightedSum / numArray.size());
+    }
+
+    private long calcPeriodNsMedian(ArrayList<Long> numArray) {
+        return median(numArray);
+    }
+
+    private long median(ArrayList<Long> numArray) {
+        numArray.sort(Comparator.naturalOrder());
+        double median;
+        if (numArray.size() % 2 == 0)
+            median = ((double)numArray.get(numArray.size()/2)
+                    + (double)numArray.get(numArray.size()/2 - 1))/2;
+        else
+            median = (double) numArray.get(numArray.size()/2);
+        return (long)median;
+    }
+
+    public void onFrameTimestamp(long timestampNs) {
+        // Register timestamp
+        if (shouldRegister) {
+            registeredTimestamps.add(timestampNs);
+        }
+    }
+
+
+}