Interfaces for injectable video codecs.

These interfaces will be used by the future refactoring that will
allow clients to provide custom codec implementations.

Change-Id: If199bc2807e1c27094c05983c62fa43d2eec5700
Bug: webrtc:7760
Reviewed-on: https://chromium-review.googlesource.com/522065
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Bjorn Mellem <mellem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18441}

webrtc/sdk/android/api/org/webrtc/VideoEncoder.java

@@ -0,0 +1,126 @@
+/*
+ *  Copyright 2017 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.webrtc;
+
+/**
+ * Interface for a video encoder that can be used with WebRTC. All calls will be made on the
+ * encoding thread.
+ */
+public interface VideoEncoder {
+  /** Settings passed to the encoder by WebRTC. */
+  public class Settings {
+    public final int numberOfCores;
+
+    public Settings(int numberOfCores) {
+      this.numberOfCores = numberOfCores;
+    }
+  }
+
+  /** Additional info for encoding. */
+  public class EncodeInfo {
+    public final EncodedImage.FrameType[] frameTypes;
+
+    public EncodeInfo(EncodedImage.FrameType[] frameTypes) {
+      this.frameTypes = frameTypes;
+    }
+  }
+
+  // TODO(sakal): Add values to these classes as necessary.
+  /** Codec specific information about the encoded frame. */
+  public class CodecSpecificInfo {}
+
+  public class CodecSpecificInfoVP8 extends CodecSpecificInfo {}
+
+  public class CodecSpecificInfoVP9 extends CodecSpecificInfo {}
+
+  public class CodecSpecificInfoH264 extends CodecSpecificInfo {}
+
+  /**
+   * Represents bitrate allocated for an encoder to produce frames. Bitrate can be divided between
+   * spatial and temporal layers.
+   */
+  public class BitrateAllocation {
+    // First index is the spatial layer and second the temporal layer.
+    public final long[][] bitratesBbs;
+
+    /**
+     * Initializes the allocation with a two dimensional array of bitrates. The first index of the
+     * array is the spatial layer and the second index in the temporal layer.
+     */
+    public BitrateAllocation(long[][] bitratesBbs) {
+      this.bitratesBbs = bitratesBbs;
+    }
+
+    /**
+     * Gets the total bitrate allocated for all layers.
+     */
+    public long getSum() {
+      long sum = 0;
+      for (long[] spatialLayer : bitratesBbs) {
+        for (long bitrate : spatialLayer) {
+          sum += bitrate;
+        }
+      }
+      return sum;
+    }
+  }
+
+  /** Settings for WebRTC quality based scaling. */
+  public class ScalingSettings {
+    public final boolean on;
+    public final int low;
+    public final int high;
+
+    /**
+     * Creates quality based scaling settings.
+     *
+     * @param on True if quality scaling is turned on.
+     * @param low Average QP at which to scale up the resolution.
+     * @param high Average QP at which to scale down the resolution.
+     */
+    public ScalingSettings(boolean on, int low, int high) {
+      this.on = on;
+      this.low = low;
+      this.high = high;
+    }
+  }
+
+  public interface Callback {
+    /** Call to return an encoded frame. */
+    void onEncodedFrame(EncodedImage frame, CodecSpecificInfo info);
+  }
+
+  /**
+   * Initializes the encoding process. Call before any calls to encode.
+   */
+  void initEncode(Settings settings, Callback encodeCallback);
+  /**
+   * Releases the encoder. No more calls to encode will be made after this call.
+   */
+  void release();
+  /**
+   * Requests the encoder to encode a frame.
+   */
+  void encode(VideoFrame frame, EncodeInfo info);
+  /**
+   * Informs the encoder of the packet loss and the round-trip time of the network.
+   *
+   * @param packetLoss How many packets are lost on average per 255 packets.
+   * @param roundTripTimeMs Round-trip time of the network in milliseconds.
+   */
+  void setChannelParameters(short packetLoss, long roundTripTimeMs);
+  /** Sets the bitrate allocation and the target framerate for the encoder. */
+  void setRateAllocation(BitrateAllocation allocation, long framerate);
+  /** Any encoder that wants to use WebRTC provided quality scaler must implement this method. */
+  ScalingSettings getScalingSettings();
+  /** Should return a descriptive name for the implementation. */
+  String getImplementationName();
+}