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// Copyright (c) 2011 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_WIN_WAVEOUT_OUTPUT_WIN_H_
#define MEDIA_AUDIO_WIN_WAVEOUT_OUTPUT_WIN_H_
#pragma once
#include <windows.h>
#include <mmsystem.h>
#include <mmreg.h>
#include "base/basictypes.h"
#include "base/win/scoped_handle.h"
#include "media/audio/audio_io.h"
#include "media/audio/audio_parameters.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 {
public:
// 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,
const AudioParameters& params,
int num_buffers,
UINT device_id);
virtual ~PCMWaveOutAudioOutputStream();
// Implementation of AudioOutputStream.
virtual bool Open();
virtual void Close();
virtual void Start(AudioSourceCallback* callback);
virtual void Stop();
virtual void SetVolume(double volume);
virtual void GetVolume(double* volume);
// Sends a buffer to the audio driver for playback.
void QueueNextPacket(WAVEHDR* buffer);
private:
enum State {
PCMA_BRAND_NEW, // Initial state.
PCMA_READY, // Device obtained and ready to play.
PCMA_PLAYING, // Playing audio.
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();
// 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 number of buffers of size |buffer_size_| each to use.
const int num_buffers_;
// The size in bytes of each audio buffer, we usually have two of these.
uint32 buffer_size_;
// Volume level from 0 to 1.
float volume_;
// Channels from 0 to 8.
const int channels_;
// Number of bytes yet to be played in the hardware buffer.
uint32 pending_bytes_;
// 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.
WAVEFORMATPCMEX format_;
// Handle to the instance of the wave device.
HWAVEOUT waveout_;
// Pointer to the first allocated audio buffer. This object owns it.
WAVEHDR* buffer_;
// Lock used to prevent stopping the hardware callback thread while it is
// pending for data or feeding it to audio driver, because doing that causes
// the deadlock. Main thread gets that lock before stopping the playback.
// Callback tries to acquire that lock before entering critical code. If
// acquire fails then main thread is stopping the playback, callback should
// immediately return.
// Use Windows-specific lock, not Chrome one, because there is limited set of
// functions callback can use.
CRITICAL_SECTION lock_;
DISALLOW_COPY_AND_ASSIGN(PCMWaveOutAudioOutputStream);
};
#endif // MEDIA_AUDIO_WIN_WAVEOUT_OUTPUT_WIN_H_
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