[chrome.displaySource] Add a base class for audio and video encoders.

extensions/renderer/api/display_source/wifi_display/wifi_display_media_encoder.h

+// Copyright 2016 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 EXTENSIONS_RENDERER_API_DISPLAY_SOURCE_WIFI_DISPLAY_WIFI_DISPLAY_MEDIA_ENCODER_H_
+#define EXTENSIONS_RENDERER_API_DISPLAY_SOURCE_WIFI_DISPLAY_WIFI_DISPLAY_MEDIA_ENCODER_H_
+
+#include <memory>
+#include <string>
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "base/move.h"
+#include "base/single_thread_task_runner.h"
+
+namespace extensions {
+
+// This structure represents an encoded media unit such as a video frame or
+// a number of audio frames.
+struct WiFiDisplayEncodedUnit {
+ public:

[Mikhail, 2016/04/20 18:58:31]

nit: 'public' is not needed in struct

[e_hakkinen, 2016/04/21 10:25:30]

Done.

+  WiFiDisplayEncodedUnit(std::string data,
+                         base::TimeTicks reference_timestamp,
+                         bool key_frame);
+  WiFiDisplayEncodedUnit(std::string data,
+                         base::TimeTicks reference_timestamp,
+                         base::TimeTicks encode_timestamp,
+                         bool key_frame);
+  WiFiDisplayEncodedUnit(const WiFiDisplayEncodedUnit&) = delete;

[Mikhail, 2016/04/20 18:58:31]

DISALLOW_COPY_AND_ASSIGN would be better

[e_hakkinen, 2016/04/20 19:22:53]

IMHO, the problem with DISALLOW_COPY_AND_ASSIGN is that it can only be used in
the private: declarion of a class, and I would like to avoid access specifiers
altogether in a struct. WDYT?

[e_hakkinen, 2016/04/21 10:25:30]

I'll use DISALLOW_ASSIGN and DISALLOW_COPY.

+
+  const uint8_t* bytes() const {
+    return reinterpret_cast<const uint8_t*>(data.data());
+  }
+  size_t size() const { return data.size(); }
+
+  std::string data;
+  base::TimeTicks pts;  // Presentation timestamp.
+  base::TimeTicks dts;  // Decoder timestamp.
+  bool key_frame;
+};
+
+// This interface is a base class for audio and video encoders used by the
+// Wi-Fi Display media pipeline.
+// Threading: the client code should belong to a single thread.
+class WiFiDisplayMediaEncoder
+    : public base::RefCountedThreadSafe<WiFiDisplayMediaEncoder> {
+ public:
+  using EncodedUnitCallback =
+      base::Callback<void(std::unique_ptr<WiFiDisplayEncodedUnit>)>;
+
+  // Sets callbacks for the obtained encoder instance:
+  // |encoded_callback| is invoked to return the next encoded unit
+  // |error_callback| is invoked to report a fatal encoder error
+  void SetCallbacks(const EncodedUnitCallback& encoded_callback,
+                    const base::Closure& error_callback);
+
+ protected:
+  friend class base::RefCountedThreadSafe<WiFiDisplayMediaEncoder>;
+
+  WiFiDisplayMediaEncoder();
+  virtual ~WiFiDisplayMediaEncoder();
+
+  EncodedUnitCallback encoded_callback_;
+  base::Closure error_callback_;
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_RENDERER_API_DISPLAY_SOURCE_WIFI_DISPLAY_WIFI_DISPLAY_MEDIA_ENCODER_H_