AppRTCDemo: Render each video in a separate SurfaceView

talk/app/webrtc/java/android/org/webrtc/RendererCommon.java

+/*
+ * libjingle
+ * Copyright 2015 Google Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *  1. Redistributions of source code must retain the above copyright notice,
+ *     this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright notice,
+ *     this list of conditions and the following disclaimer in the documentation
+ *     and/or other materials provided with the distribution.
+ *  3. The name of the author may not be used to endorse or promote products
+ *     derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+ * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.webrtc;
+
+import android.graphics.Point;
+import android.opengl.Matrix;
+
+/**
+ * Static helper functions for VideoRendererGui and SurfaceViewRenderer.
+ */
+public class RendererCommon {
+  // Types of video scaling:
+  // SCALE_ASPECT_FIT - video frame is scaled to fit the size of the view by
+  //    maintaining the aspect ratio (black borders may be displayed).
+  // SCALE_ASPECT_FILL - video frame is scaled to fill the size of the view by
+  //    maintaining the aspect ratio. Some portion of the video frame may be
+  //    clipped.
+  // SCALE_ASPECT_BALANCED - Compromise between FIT and FILL. Video frame will fill as much as
+  // possible of the view while maintaining aspect ratio, under the constraint that at least
+  // |BALANCED_VISIBLE_FRACTION| of the frame content will be shown.
+  public static enum ScalingType { SCALE_ASPECT_FIT, SCALE_ASPECT_FILL, SCALE_ASPECT_BALANCED }
+  // The minimum fraction of the frame content that will be shown for |SCALE_ASPECT_BALANCED|.
+  // This limits excessive cropping when adjusting display size.
+  private static float BALANCED_VISIBLE_FRACTION = 0.56f;
+
+  /**
+   * Calculates a texture transformation matrix based on rotation, mirror, and video vs display
+   * aspect ratio.
+   */
+  public static void getTextureMatrix(float[] outputTextureMatrix, float rotationDegree,
+      boolean mirror, float videoAspectRatio, float displayAspectRatio) {
+    // The matrix stack is using post-multiplication, which means that matrix operations:
+    // A; B; C; will end up as A * B * C. When you apply this to a vertex, it will result in:
+    // v' = A * B * C * v, i.e. the last matrix operation is the first thing that affects the
+    // vertex. This is the opposite of what you might expect.
+    Matrix.setIdentityM(outputTextureMatrix, 0);
+    // Move coordinates back to [0,1]x[0,1].
+    Matrix.translateM(outputTextureMatrix, 0, 0.5f, 0.5f, 0.0f);
+    // Rotate frame clockwise in the XY-plane (around the Z-axis).
+    Matrix.rotateM(outputTextureMatrix, 0, -rotationDegree, 0, 0, 1);
+    // Scale one dimension until video and display size have same aspect ratio.
+    if (displayAspectRatio > videoAspectRatio) {
+      Matrix.scaleM(outputTextureMatrix, 0, 1, videoAspectRatio / displayAspectRatio, 1);
+    } else {
+      Matrix.scaleM(outputTextureMatrix, 0, displayAspectRatio / videoAspectRatio, 1, 1);
+    }
+    // TODO(magjed): We currently ignore the texture transform matrix from the SurfaceTexture.
+    // It contains a vertical flip that is hardcoded here instead.
+    Matrix.scaleM(outputTextureMatrix, 0, 1, -1, 1);
+    // Apply optional horizontal flip.
+    if (mirror) {
+      Matrix.scaleM(outputTextureMatrix, 0, -1, 1, 1);
+    }
+    // Center coordinates around origin.
+    Matrix.translateM(outputTextureMatrix, 0, -0.5f, -0.5f, 0.0f);
+  }
+
+  /**
+   * Calculate display size based on scaling type, video aspect ratio, and maximum display size.
+   */
+  public static Point getDisplaySize(ScalingType scalingType, float videoAspectRatio,
+      int maxDisplayWidth, int maxDisplayHeight) {
+    return getDisplaySize(convertScalingTypeToVisibleFraction(scalingType), videoAspectRatio,
+        maxDisplayWidth, maxDisplayHeight);
+  }
+
+  /**
+   * Each scaling type has a one-to-one correspondence to a numeric minimum fraction of the video
+   * that must remain visible.
+   */
+  private static float convertScalingTypeToVisibleFraction(ScalingType scalingType) {
+    switch (scalingType) {
+      case SCALE_ASPECT_FIT:
+        return 1.0f;
+      case SCALE_ASPECT_FILL:
+        return 0.0f;
+      case SCALE_ASPECT_BALANCED:
+        return BALANCED_VISIBLE_FRACTION;
+      default:
+        throw new IllegalArgumentException();
+    }
+  }
+
+  /**
+   * Calculate display size based on minimum fraction of the video that must remain visible,
+   * video aspect ratio, and maximum display size.
+   */
+  private static Point getDisplaySize(float minVisibleFraction, float videoAspectRatio,
+      int maxDisplayWidth, int maxDisplayHeight) {
+    // If there is no constraint on the amount of cropping, fill the allowed display area.
+    if (minVisibleFraction == 0 || videoAspectRatio == 0) {
+      return new Point(maxDisplayWidth, maxDisplayHeight);
+    }
+    // Each dimension is constrained on max display size and how much we are allowed to crop.
+    final int width = Math.min(maxDisplayWidth,
+        (int) (maxDisplayHeight / minVisibleFraction * videoAspectRatio));
+    final int height = Math.min(maxDisplayHeight,
+        (int) (maxDisplayWidth / minVisibleFraction / videoAspectRatio));
+    return new Point(width, height);
+  }
+}