Android AppRTCDemo: Add slider for changing camera capture quality during call

webrtc/examples/androidapp/src/org/appspot/apprtc/CaptureQualityController.java

+/*
+ *  Copyright 2015 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+package org.appspot.apprtc;
+
+import android.widget.SeekBar;
+import android.widget.TextView;
+
+import org.webrtc.CameraEnumerationAndroid.CaptureFormat;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+/**
+ * Control capture format based on a seekbar listener.
+ */
+public class CaptureQualityController implements SeekBar.OnSeekBarChangeListener {
+  private final List<CaptureFormat> formats = Arrays.asList(
+      new CaptureFormat(1280, 720, 0, 30000),
+      new CaptureFormat(640, 480, 0, 30000),
+      new CaptureFormat(320, 240, 0, 30000),
+      new CaptureFormat(256, 144, 0, 30000));
+  // Prioritize framerate below this threshold and resolution above the threshold.
+  private static final int FRAMERATE_THRESHOLD = 15;
+  private TextView captureFormatText;
+  private CallFragment.OnCallEvents callEvents;
+  private int width = 0;
+  private int height = 0;
+  private int framerate = 0;
+  private double targetBandwidth = 0;
+
+  public CaptureQualityController(
+      TextView captureFormatText, CallFragment.OnCallEvents callEvents) {
+    this.captureFormatText = captureFormatText;
+    this.callEvents = callEvents;
+    captureFormatText.setText("Slide to change capture format");
+  }
+
+  private final Comparator<CaptureFormat> compareFormats = new Comparator<CaptureFormat>() {
+    @Override
+    public int compare(CaptureFormat first, CaptureFormat second) {
+      int firstFps = calculateFramerate(targetBandwidth, first);
+      int secondFps = calculateFramerate(targetBandwidth, second);
+
+     if (firstFps >= FRAMERATE_THRESHOLD && secondFps >= FRAMERATE_THRESHOLD
+         || firstFps == secondFps) {
+        // Compare resolution.
+        return first.width * first.height - second.width * second.height;
+     } else {
+        // Compare fps.
+        return firstFps - secondFps;
+     }
+    }
+  };
+
+  @Override
+  public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
+    if (progress == 0) {
+      width = 0;
+      height = 0;
+      framerate = 0;
+      captureFormatText.setText("Muted");
+      return;
+    }
+
+    // Extract max bandwidth (in millipixels / second).
+    long maxCaptureBandwidth = java.lang.Long.MIN_VALUE;
+    for (CaptureFormat format : formats) {
+      maxCaptureBandwidth = Math.max(maxCaptureBandwidth,
+          (long) format.width * format.height * format.maxFramerate);
+    }
+
+    // Fraction between 0 and 1.
+    double bandwidthFraction = (double) progress / 100.0;
+    // Make a log-scale transformation, still between 0 and 1.
+    final double kExpConstant = 3.0;
+    bandwidthFraction =
+        (Math.exp(kExpConstant * bandwidthFraction) - 1) / (Math.exp(kExpConstant) - 1);
+    targetBandwidth = bandwidthFraction * maxCaptureBandwidth;
+
+    // Choose the best format given a target bandwidth.
+    final CaptureFormat bestFormat = Collections.max(formats, compareFormats);
+    width = bestFormat.width;
+    height = bestFormat.height;
+    framerate = calculateFramerate(targetBandwidth, bestFormat);
+    captureFormatText.setText(width + "x" + height + " @ " + framerate + "fps");
+  }
+
+  @Override
+  public void onStartTrackingTouch(SeekBar seekBar) {
+  }
+
+  @Override
+  public void onStopTrackingTouch(SeekBar seekBar) {
+    callEvents.onCaptureFormatChange(width, height, framerate);
+  }
+
+  // Return the highest frame rate possible based on bandwidth and format.
+  private int calculateFramerate(double bandwidth, CaptureFormat format) {
+    return (int) Math.round(Math.min(format.maxFramerate,
+        (int) Math.round(bandwidth / (format.width * format.height))) / 1000.0);
+  }
+}
+