[Cast] Compute utilization metrics and add performance overlay.

media/cast/sender/performance_metrics_overlay.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_CAST_SENDER_PERFORMANCE_METRICS_OVERLAY_H_
+#define MEDIA_CAST_SENDER_PERFORMANCE_METRICS_OVERLAY_H_
+
+// This module provides a display of frame-level performance metrics, rendered
+// in the lower-right corner of a VideoFrame.  It looks like this:
+//
+// +----------------------------------------------------------------+
+// |                         @@@@@@@@@@@@@@@@@@@@@@@                |
+// |                 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@                |
+// |              @@@@@@@@@@@@@@@@@@@@@@@ @@@@@@@@@@@@              |
+// |             @@@@@@@@@@@@@                    @@@@              |
+// |            @@@@@@@@@@                        @@@@              |
+// |           @@@@@  @@@               @@@       @@@@              |
+// |           @@@     @    @@@         @@@@      @@@@              |
+// |          @@@@          @@@@                  @@@@              |
+// |          @@@@                  @@@           @@@               |
+// |            @@@@                 @@           @@@               |
+// |             @@@@@      @@@            @@@   @@@                |
+// |              @@@@@     @@@@@        @@@@   @@@@                |
+// |               @@@@@      @@@@@@@@@@@@@    @@@@                 |
+// |                @@@@@@                    @@@@      1  45%  75% |
+// |                    @@@@@@@@         @@@@@@      22  16.7  4000 |
+// |                         @@@@@@@@@@@@@@@@      1280x720 0:15.12 |
+// +----------------------------------------------------------------+
+//
+// Line 1: Reads as, "1 frame ago, the encoder deadline utilization for the
+// frame was 45% and the lossy utilization was 75%."  Encoder deadline
+// utilization is in terms the amount of real-world time it took to encode the
+// frame, divided by the maximum amount of time allowed.  Lossy utilization is
+// the amount of "complexity" in the frame's content versus the target encoded
+// byte size, where a value over 100% means the frame's content is too complex
+// to encode within the target number of bytes.
+//
+// Line 2: Reads as, "Capture of this frame took 22 ms.  The expected duration
+// of this frame is 16.7 ms.  The target bitrate for this frame is 4000 kbps."
+//
+// Line 3: Contains the frame's resolution and media timestamp in
+// minutes:seconds.hundredths format.
+
+namespace media {
+
+class VideoFrame;
+
+namespace cast {
+
+// Renders an overlay of frame-level performance metrics in the lower-right
+// corner of the |frame|, as described above.  The verbose logging level for
+// video_frame_overlay.cc determines which lines, if any, are rendered: VLOG
+// level 1 renders the bottom line only, level 2 renders the bottom and middle
+// lines, and level 3 renders all three lines.  So, use the
+// --vmodule=performance_metrics_overlay=3 command line argument to turn on
+// rendering of the entire overlay.
+void MaybeRenderPerformanceMetricsOverlay(int target_bitrate,
+                                          int frames_ago,
+                                          double deadline_utilization,
+                                          double lossy_utilization,
+                                          VideoFrame* frame);
+
+}  // namespace cast
+}  // namespace media
+
+#endif  // MEDIA_CAST_SENDER_PERFORMANCE_METRICS_OVERLAY_H_