Add initial keyframe tests

Implements a couple simple tests of the encoder API using the gtest
framework:

  TestDisableKeyframes
  TestForceKeyframe
  TestKeyframeMaxDistance

Change-Id: I38e93fe242fbeb30bb11b23ac12de8ddc291a28d

test/video_source.h

diff --git a/test/video_source.h b/test/video_source.h
new file mode 100644
index 0000000..86c6caa
--- /dev/null
+++ b/test/video_source.h
@@ -0,0 +1,109 @@
+/*
+ *  Copyright (c) 2012 The WebM 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.
+ */
+#ifndef TEST_VIDEO_SOURCE_H_
+#define TEST_VIDEO_SOURCE_H_
+#include "vpx/vpx_encoder.h"
+
+namespace libvpx_test {
+
+// Abstract base class for test video sources, which provide a stream of
+// vpx_image_t images with associated timestamps and duration.
+class VideoSource {
+ public:
+  virtual ~VideoSource() {}
+
+  // Prepare the stream for reading, rewind/open as necessary.
+  virtual void Begin() = 0;
+
+  // Advance the cursor to the next frame
+  virtual void Next() = 0;
+
+  // Get the current video frame, or NULL on End-Of-Stream.
+  virtual vpx_image_t *img() const = 0;
+
+  // Get the presentation timestamp of the current frame.
+  virtual vpx_codec_pts_t pts() const = 0;
+
+  // Get the current frame's duration
+  virtual unsigned long duration() const = 0;
+
+  // Get the timebase for the stream
+  virtual vpx_rational_t timebase() const = 0;
+
+  // Get the current frame counter, starting at 0.
+  virtual unsigned int frame() const = 0;
+};
+
+
+class DummyVideoSource : public VideoSource {
+ public:
+  DummyVideoSource()
+    : img_(NULL), limit_(100) { SetSize(80, 64); }
+
+  virtual ~DummyVideoSource() { vpx_img_free(img_); }
+
+  virtual void Begin() {
+    frame_ = 0;
+    FillFrame();
+  }
+
+  virtual void Next() {
+    ++frame_;
+    FillFrame();
+  }
+
+  virtual vpx_image_t *img() const {
+    return (frame_ < limit_) ? img_ : NULL;
+  }
+
+  // Models a stream where Timebase = 1/FPS, so pts == frame.
+  virtual vpx_codec_pts_t pts() const { return frame_; }
+
+  virtual unsigned long duration() const { return 1; }
+
+  virtual vpx_rational_t timebase() const {
+    const vpx_rational_t t = {1, 30};
+    return t;
+  }
+
+  virtual unsigned int frame() const { return frame_; }
+
+  void SetSize(unsigned int width, unsigned int height) {
+    vpx_img_free(img_);
+    raw_sz_ = ((width + 31)&~31) * height * 3 / 2;
+    img_ = vpx_img_alloc(NULL, VPX_IMG_FMT_VPXI420, width, height, 32);
+  }
+
+ protected:
+  virtual void FillFrame() { memset(img_->img_data, 0, raw_sz_); }
+
+  vpx_image_t *img_;
+  size_t       raw_sz_;
+  unsigned int limit_;
+  unsigned int frame_;
+};
+
+
+class RandomVideoSource : public DummyVideoSource {
+ protected:
+  // 15 frames of noise, followed by 15 static frames. Reset to 0 rather
+  // than holding previous frames to encourage keyframes to be thrown.
+  virtual void FillFrame() {
+    if (frame_ % 30 < 15)
+      for (size_t i = 0; i < raw_sz_; ++i)
+        img_->img_data[i] = rand();
+    else
+      memset(img_->img_data, 0, raw_sz_);
+  }
+};
+
+}  // namespace libvpx_test
+
+#endif  // TEST_VIDEO_SOURCE_H_