Access unit queue for MediaCodecPlayer

media/base/android/access_unit_queue.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_BASE_ANDROID_ACCESS_UNIT_QUEUE_H_
+#define MEDIA_BASE_ANDROID_ACCESS_UNIT_QUEUE_H_
+
+#include <list>
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/synchronization/lock.h"
+#include "media/base/android/demuxer_stream_player_params.h"
+
+namespace media {
+
+// The queue of incoming data for MediaCodecDecoder.
+//
+// The data comes in the form of access units. Each access unit has a type.
+// If the type is |kConfigChanged| the access unit itself has no data, but
+// is accompanied with DemuxerConfigs.
+// The queue should be accessed on the Media thread that puts the incoming data
+// in and on the Decoder thread that gets the next access unit and eventually
+// removes it from the queue.
+class AccessUnitQueue {
+ public:
+  // Information about the queue state and the access unit at the front.
+  struct Info {
+    // The unit at front. Null if the queue is empty. This pointer may be
+    // invalidated by the next Advance() or Flush() call and must be used
+    // before the caller calls these methods.

[wolenetz, 2015/06/12 22:05:19]

nit: Clarify in comment(s) here and/or GetInfo() that the AccessUnitQueue owns
the pointers; the caller should not delete |front_unit| or |configs|.

[Tima Vaisburd, 2015/06/12 22:44:01]

Done.

+    const AccessUnit* front_unit;
+
+    // Configs for the front unit if it is |kConfigChanged|, null otherwise.
+    // The same validity rule applies: this pointer is only valid till the next
+    // Advance() or Flush() call.
+    const DemuxerConfigs* configs;
+
+    // Number of access units in the queue.
+    int length;
+
+    // Whether End Of Stream has been added to the queue. Cleared by Flush().
+    bool has_eos;
+
+    Info() : front_unit(nullptr), configs(nullptr), length(0), has_eos(false) {}
+  };
+
+  AccessUnitQueue();
+  ~AccessUnitQueue();
+
+  // Appends the incoming data to the queue.
+  void PushBack(const DemuxerData& frames);
+
+  // Advances the front position to next unit. Logically the preceding units
+  // do not exist, but they can be physically removed later.
+  void Advance();
+
+  // Clears the queue, resets the length to zero and clears EOS condition.
+  void Flush();
+
+  // Looks back for the first key frame starting from the current one (i.e.
+  // the look-back is inclusive of the current front position).
+  // If the key frame exists, sets the current access unit to it and returns
+  // true. Otherwise returns false.
+  bool RewindToLastKeyFrame();
+
+  // Returns the information about the queue.
+  // The result is invalidated by the following Advance() or Flush call.
+  // There must be only one |Info| consumer at a time.
+  Info GetInfo() const;
+
+  // For unit tests only. These methods are not thread safe.
+  size_t NumChunksForTesting() const { return chunks_.size(); }
+  void SetHistorySizeForTesting(size_t number_of_history_chunks);
+
+ private:
+  // Returns the amount of access units between the current one and the end,
+  // incuding current. Logically these are units that have not been consumed.
+  int GetUnconsumedAccessUnitLength() const;
+
+  // The queue of data chunks. It owns the chunks.
+  typedef std::list<DemuxerData*> DataChunkQueue;
+  DataChunkQueue chunks_;
+
+  // The chunk that contains the current access unit.
+  DataChunkQueue::iterator current_chunk_;
+
+  // Index of the current access unit within the current chunk.
+  size_t index_in_chunk_;
+
+  // Amount of chunks before the |current_chunk_| that's kept for history.
+  size_t history_chunks_amount_;
+
+  // Indicates that a unit with End Of Stream flag has been appended.
+  bool has_eos_;
+
+  // The lock protects all fields together.
+  mutable base::Lock lock_;
+
+  DISALLOW_COPY_AND_ASSIGN(AccessUnitQueue);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_ANDROID_ACCESS_UNIT_QUEUE_H_