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// Copyright (c) 2009 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.
// AudioRendererBase takes care of the tricky queuing work and provides simple
// methods for subclasses to peek and poke at audio data. In addition to
// AudioRenderer interface methods this classes doesn't implement, subclasses
// must also implement the following methods:
// OnInitialized
// OnStop
//
// The general assumption is that subclasses start a callback-based audio thread
// which needs to be filled with decoded audio data. AudioDecoderBase provides
// FillBuffer which handles filling the provided buffer, dequeuing items,
// scheduling additional reads and updating the clock. In a sense,
// AudioRendererBase is the producer and the subclass is the consumer.
#ifndef MEDIA_FILTERS_AUDIO_RENDERER_BASE_H_
#define MEDIA_FILTERS_AUDIO_RENDERER_BASE_H_
#include <deque>
#include "base/lock.h"
#include "media/base/buffers.h"
#include "media/base/factory.h"
#include "media/base/filters.h"
namespace media {
class AudioRendererBase : public AudioRenderer {
public:
// MediaFilter implementation.
virtual void Stop();
// AudioRenderer implementation.
virtual bool Initialize(AudioDecoder* decoder);
// AssignableBuffer<AudioRendererBase, BufferInterface> implementation.
void OnAssignment(Buffer* buffer_in);
protected:
// The default maximum size of the queue.
static const size_t kDefaultMaxQueueSize;
// Only allow a factory to create this class.
AudioRendererBase(size_t max_queue_size);
virtual ~AudioRendererBase();
// Called by Initialize(). |media_format| is the format of the AudioDecoder.
// Subclasses should return true if they were able to initialize, false
// otherwise.
virtual bool OnInitialize(const MediaFormat* media_format) = 0;
// Called by Stop(). Subclasses should perform any necessary cleanup during
// this time, such as stopping any running threads.
virtual void OnStop() = 0;
// Fills the given buffer with audio data by dequeuing buffers and copying the
// data into the |dest|. FillBuffer also takes care of updating the clock.
// Returns the number of bytes copied into |dest|, which may be less than
// equal to |len|.
//
// If this method is returns less bytes than |len| (including zero), it could
// be a sign that the pipeline is stalled or unable to stream the data fast
// enough. In such scenarios, the callee should zero out unused portions
// of their buffer to playback silence.
//
// Safe to call on any thread.
size_t FillBuffer(uint8* dest, size_t len);
// Helper to parse a media format and return whether we were successful
// retrieving all the information we care about.
static bool ParseMediaFormat(const MediaFormat* media_format,
int* channels_out, int* sample_rate_out,
int* sample_bits_out);
private:
// Audio decoder.
AudioDecoder* decoder_;
// Maximum queue size, configuration parameter passed in during construction.
size_t max_queue_size_;
// Queued audio data.
typedef std::deque<Buffer*> BufferQueue;
BufferQueue queue_;
Lock lock_;
// Remembers the amount of remaining audio data for the front buffer.
size_t data_offset_;
// Whether or not we're initialized.
bool initialized_;
// Whether or not we've stopped.
bool stopped_;
// Posts a task on the pipeline thread to read a sample from the decoder. The
// resulting buffer will be placed in the queue.
//
// Safe to call on any thread.
void ScheduleRead();
DISALLOW_COPY_AND_ASSIGN(AudioRendererBase);
};
} // namespace media
#endif // MEDIA_FILTERS_AUDIO_RENDERER_BASE_H_
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