1 // Copyright 2019 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifndef MEDIA_BLINK_SMOOTHNESS_HELPER_H_
6 #define MEDIA_BLINK_SMOOTHNESS_HELPER_H_
7 
8 #include <memory>
9 
10 #include "media/base/buffering_state.h"
11 #include "media/base/pipeline_status.h"
12 #include "media/blink/media_blink_export.h"
13 #include "media/learning/common/labelled_example.h"
14 
15 namespace media {
16 
17 namespace learning {
18 class LearningTaskController;
19 }
20 
21 // Helper class to construct learning observations about the smoothness of a
22 // video playback.  Currently measures the worst-case frame drop ratio observed
23 // among fixed-length segments.
24 class MEDIA_BLINK_EXPORT SmoothnessHelper {
25  public:
26   // Callback that provides the number of dropped / decoded frames since some
27   // point in the past.  We assume that these values are comparable during
28   // playback, so that we can compute deltas.
29   class Client {
30    public:
~Client()31     virtual ~Client() {}
32 
33     virtual unsigned DecodedFrameCount() const = 0;
34     virtual unsigned DroppedFrameCount() const = 0;
35   };
36 
37   virtual ~SmoothnessHelper();
38 
39   // Return the features that we were constructed with.
features()40   const learning::FeatureVector& features() const { return features_; }
41 
42   // Notify us that an NNR has occurred.
43   virtual void NotifyNNR() = 0;
44 
45   // |features| are the features that we'll use for any labelled examples that
46   // we create.  They should be features that could be captured at the time a
47   // prediction would be needed.
48   static std::unique_ptr<SmoothnessHelper> Create(
49       std::unique_ptr<learning::LearningTaskController> bad_controller,
50       std::unique_ptr<learning::LearningTaskController> nnr_controller,
51       const learning::FeatureVector& features,
52       Client* player);
53 
54   // We split playbacks up into |kSegmentSize| units, and record the worst
55   // dropped frame ratio over all segments of a playback.  A playback is not
56   // recorded if it doesn't contain at least one full segment.
57   static base::TimeDelta SegmentSizeForTesting();
58 
59  protected:
60   SmoothnessHelper(const learning::FeatureVector& features);
61 
62   learning::FeatureVector features_;
63 };
64 
65 }  // namespace media
66 
67 #endif  // MEDIA_BLINK_SMOOTHNESS_HELPER_H_
68