// Copyright 2013 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_AUDIO_BUFFER_QUEUE_H_ #define MEDIA_BASE_AUDIO_BUFFER_QUEUE_H_ #include <deque> #include "base/basictypes.h" #include "base/memory/scoped_ptr.h" #include "media/base/audio_buffer.h" #include "media/base/media_export.h" namespace media { class AudioBus; // A queue of AudioBuffers to support reading of arbitrary chunks of a media // data source. Audio data can be copied into an AudioBus for output. The // current position can be forwarded to anywhere in the buffered data. // // This class is not inherently thread-safe. Concurrent access must be // externally serialized. class MEDIA_EXPORT AudioBufferQueue { public: AudioBufferQueue(); ~AudioBufferQueue(); // Clears the buffer queue. void Clear(); // Appends |buffer_in| to this queue. void Append(const scoped_refptr<AudioBuffer>& buffer_in); // Reads a maximum of |frames| frames into |dest| from the current position. // Returns the number of frames read. The current position will advance by the // amount of frames read. |dest_frame_offset| specifies a starting offset into // |dest|. On each call, the frames are converted from their source format // into the destination AudioBus. int ReadFrames(int frames, int dest_frame_offset, AudioBus* dest); // Copies up to |frames| frames from current position to |dest|. Returns // number of frames copied. Doesn't advance current position. Starts at // |source_frame_offset| from current position. |dest_frame_offset| specifies // a starting offset into |dest|. On each call, the frames are converted from // their source format into the destination AudioBus. int PeekFrames(int frames, int source_frame_offset, int dest_frame_offset, AudioBus* dest); // Moves the current position forward by |frames| frames. If |frames| exceeds // frames available, the seek operation will fail. void SeekFrames(int frames); // Returns the number of frames buffered beyond the current position. int frames() const { return frames_; } // Returns the current timestamp, taking into account current offset. The // value calculated based on the timestamp of the current buffer. If timestamp // for the current buffer is set to 0, then returns value that corresponds to // the last position in a buffer that had timestamp set. kNoTimestamp() is // returned if no buffers we read from had timestamp set. base::TimeDelta current_time() const { return current_time_; } private: // Definition of the buffer queue. typedef std::deque<scoped_refptr<AudioBuffer> > BufferQueue; // An internal method shared by ReadFrames() and SeekFrames() that actually // does reading. It reads a maximum of |frames| frames into |dest|. Returns // the number of frames read. The current position will be moved forward by // the number of frames read if |advance_position| is set. If |dest| is NULL, // only the current position will advance but no data will be copied. // |source_frame_offset| can be used to skip frames before reading. // |dest_frame_offset| specifies a starting offset into |dest|. int InternalRead(int frames, bool advance_position, int source_frame_offset, int dest_frame_offset, AudioBus* dest); // Updates |current_time_| with the time that corresponds to the specified // position in the buffer. void UpdateCurrentTime(BufferQueue::iterator buffer, int offset); BufferQueue::iterator current_buffer_; BufferQueue buffers_; int current_buffer_offset_; // Number of frames available to be read in the buffer. int frames_; // Keeps track of the most recent time we've seen in case the |buffers_| is // empty when our owner asks what time it is. base::TimeDelta current_time_; DISALLOW_COPY_AND_ASSIGN(AudioBufferQueue); }; } // namespace media #endif // MEDIA_BASE_AUDIO_BUFFER_QUEUE_H_