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// Copyright (c) 2010 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_AUDIO_AUDIO_MANAGER_H_
#define MEDIA_AUDIO_AUDIO_MANAGER_H_
#include "base/basictypes.h"
class AudioInputStream;
class AudioOutputStream;
class MessageLoop;
// Manages all audio resources. In particular it owns the AudioOutputStream
// objects. Provides some convenience functions that avoid the need to provide
// iterators over the existing streams.
class AudioManager {
public:
enum Format {
AUDIO_PCM_LINEAR = 0, // PCM is 'raw' amplitude samples.
AUDIO_PCM_LOW_LATENCY, // Linear PCM, low latency requested.
AUDIO_MOCK, // Creates a dummy AudioOutputStream object.
AUDIO_LAST_FORMAT // Only used for validation of format.
};
// Telephone quality sample rate, mostly for speech-only audio.
static const uint32 kTelephoneSampleRate = 8000;
// CD sampling rate is 44.1 KHz or conveniently 2x2x3x3x5x5x7x7.
static const uint32 kAudioCDSampleRate = 44100;
// Digital Audio Tape sample rate.
static const uint32 kAudioDATSampleRate = 48000;
// Returns true if the OS reports existence of audio devices. This does not
// guarantee that the existing devices support all formats and sample rates.
virtual bool HasAudioOutputDevices() = 0;
// Returns true if the OS reports existence of audio recording devices. This
// does not guarantee that the existing devices support all formats and
// sample rates.
virtual bool HasAudioInputDevices() = 0;
// Factory for all the supported stream formats. The |channels| can be 1 to 5.
// The |sample_rate| is in hertz and can be any value supported by the
// platform. For some future formats the |sample_rate| and |bits_per_sample|
// can take special values.
// Returns NULL if the combination of the parameters is not supported, or if
// we have reached some other platform specific limit.
//
// AUDIO_PCM_LOW_LATENCY can be passed to this method and it has two effects:
// 1- Instead of triple buffered the audio will be double buffered.
// 2- A low latency driver or alternative audio subsystem will be used when
// available.
//
// Do not free the returned AudioOutputStream. It is owned by AudioManager.
virtual AudioOutputStream* MakeAudioOutputStream(Format format, int channels,
int sample_rate,
char bits_per_sample) = 0;
// Factory to create audio recording streams.
// |channels| can be 1 or 2.
// |sample_rate| is in hertz and can be any value supported by the platform.
// |bits_per_sample| can be any value supported by the platform.
// |samples_per_packet| is in hertz as well and can be 0 to |sample_rate|,
// with 0 suggesting that the implementation use a default value for that
// platform.
// Returns NULL if the combination of the parameters is not supported, or if
// we have reached some other platform specific limit.
//
// Do not free the returned AudioInputStream. It is owned by AudioManager.
// When you are done with it, call |Stop()| and |Close()| to release it.
virtual AudioInputStream* MakeAudioInputStream(Format format, int channels,
int sample_rate,
char bits_per_sample,
uint32 samples_per_packet) = 0;
// Muting continues playback but effectively the volume is set to zero.
// Un-muting returns the volume to the previous level.
virtual void MuteAll() = 0;
virtual void UnMuteAll() = 0;
// Returns message loop used for audio IO.
virtual MessageLoop* GetMessageLoop() = 0;
// Get AudioManager singleton.
// TODO(cpu): Define threading requirements for interacting with AudioManager.
static AudioManager* GetAudioManager();
protected:
virtual ~AudioManager() {}
// Called from GetAudioManager() to initialiaze the instance.
virtual void Init() = 0;
private:
static void Destroy(void*);
// Called by GetAudioManager() to create platform-specific audio manager.
static AudioManager* CreateAudioManager();
};
#endif // MEDIA_AUDIO_AUDIO_MANAGER_H_
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