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// 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 "base/containers/circular_deque.h"
#include "base/macros.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(const AudioBufferQueue&) = delete;
AudioBufferQueue& operator=(const AudioBufferQueue&) = delete;
~AudioBufferQueue();
// Clears the buffer queue.
void Clear();
// Appends |buffer_in| to this queue.
void Append(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_; }
private:
// Definition of the buffer queue.
using BufferQueue = base::circular_deque<scoped_refptr<AudioBuffer>>;
// 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);
BufferQueue buffers_;
int front_buffer_offset_; // Offset into buffers_.front().
// Number of frames available to be read in the buffer.
int frames_;
};
} // namespace media
#endif // MEDIA_BASE_AUDIO_BUFFER_QUEUE_H_