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// Copyright (c) 2006-2008 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.
#include <windows.h>
#include <mmsystem.h>
#include "base/basictypes.h"
#include "base/scoped_handle_win.h"
#include "media/audio/audio_output.h"
class AudioManagerWin;
// Implements PCM audio output support for Windows using the WaveXXX API.
// While not as nice as the DirectSound-based API, it should work in all target
// operating systems regardless or DirectX version installed. It is known that
// in some machines WaveXXX based audio is better while in others DirectSound
// is better.
// Important: the OnXXXX functions in AudioSourceCallback are called by more
// than one thread so it is important to have some form of synchronization if
// you are keeping state in it.
class PCMWaveOutAudioOutputStream : public AudioOutputStream {
// The ctor takes all the usual parameters, plus |manager| which is the
// the audio manager who is creating this object and |device_id| which
// is provided by the operating system.
PCMWaveOutAudioOutputStream(AudioManagerWin* manager,
int channels, int sampling_rate,
char bits_per_sample, UINT device_id);
virtual ~PCMWaveOutAudioOutputStream();
// Implementation of AudioOutputStream.
virtual bool Open(size_t packet_size);
virtual void Close();
virtual void Start(AudioSourceCallback* callback);
virtual void Stop();
virtual void SetVolume(double left_level, double right_level);
virtual void GetVolume(double* left_level, double* right_level);
// Sends a buffer to the audio driver for playback.
void QueueNextPacket(WAVEHDR* buffer);
enum State {
PCMA_BRAND_NEW, // Initial state.
PCMA_READY, // Device obtained and ready to play.
PCMA_PLAYING, // Playing audio.
PCMA_STOPPING, // Trying to stop, waiting for callback to finish.
PCMA_STOPPED, // Stopped. Device was reset.
PCMA_CLOSED // Device has been released.
// Windows calls us back to feed more data to the device here. See msdn
// documentation for 'waveOutProc' for details about the parameters.
static void CALLBACK WaveCallback(HWAVEOUT hwo, UINT msg, DWORD_PTR instance,
DWORD_PTR param1, DWORD_PTR param2);
// If windows reports an error this function handles it and passes it to
// the attached AudioSourceCallback::OnError().
void HandleError(MMRESULT error);
// Allocates and prepares the memory that will be used for playback. Only
// two buffers are created.
void SetupBuffers(size_t rq_size);
// Deallocates the memory allocated in SetupBuffers.
void FreeBuffers();
// Reader beware. Visual C has stronger guarantees on volatile vars than
// most people expect. In fact, it has release semantics on write and
// acquire semantics on reads. See the msdn documentation.
volatile State state_;
// The audio manager that created this output stream. We notify it when
// we close so it can release its own resources.
AudioManagerWin* manager_;
// We use the callback mostly to periodically request more audio data.
AudioSourceCallback* callback_;
// The size in bytes of each audio buffer, we usually have two of these.
size_t buffer_size_;
// The id assigned by the operating system to the selected wave output
// hardware device. Usually this is just -1 which means 'default device'.
UINT device_id_;
// Windows native structure to encode the format parameters.
// Handle to the instance of the wave device.
HWAVEOUT waveout_;
// Pointer to the first allocated audio buffer. This object owns it.
WAVEHDR* buffer_;
// An event that is signaled when the callback thread is ready to stop.
ScopedHandle stopped_event_;