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// Copyright (c) 2012 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_PULL_FIFO_H_
#define MEDIA_BASE_AUDIO_PULL_FIFO_H_
#include "base/callback.h"
#include "media/base/media_export.h"
namespace media {
class AudioBus;
// A FIFO (First In First Out) buffer to handle mismatches in buffer sizes
// between a producer and consumer. The consumer will pull data from this FIFO.
// If data is already available in the FIFO, it is provided to the consumer.
// If insufficient data is available to satisfy the request, the FIFO will ask
// the producer for more data to fulfill a request.
class MEDIA_EXPORT AudioPullFifo {
public:
// Callback type for providing more data into the FIFO. Expects AudioBus
// to be completely filled with data upon return; zero padded if not enough
// frames are available to satisfy the request. |frame_delay| is the number
// of output frames already processed and can be used to estimate delay.
typedef base::Callback<void(int frame_delay, AudioBus* audio_bus)> ReadCB;
// Constructs an AudioPullFifo with the specified |read_cb|, which is used to
// read audio data to the FIFO if data is not already available. The internal
// FIFO can contain |channel| number of channels, where each channel is of
// length |frames| audio frames.
AudioPullFifo(int channels, int frames, const ReadCB& read_cb);
virtual ~AudioPullFifo();
// Consumes |frames_to_consume| audio frames from the FIFO and copies
// them to |destination|. If the FIFO does not have enough data, we ask
// the producer to give us more data to fulfill the request using the
// ReadCB implementation.
void Consume(AudioBus* destination, int frames_to_consume);
// Empties the FIFO without deallocating any memory.
void Clear();
private:
// Attempt to fulfill the request using what is available in the FIFO.
// Append new data to the |destination| starting at |write_pos|.
int ReadFromFifo(AudioBus* destination, int frames_to_provide, int write_pos);
// Source of data to the FIFO.
const ReadCB read_cb_;
// Temporary audio bus to hold the data from the producer.
scoped_ptr<AudioBus> fifo_;
int fifo_index_;
DISALLOW_COPY_AND_ASSIGN(AudioPullFifo);
};
} // namespace media
#endif // MEDIA_BASE_AUDIO_PULL_FIFO_H_
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