Low level windows audio support (part 2 of 2)

- Implementation using the WaveXXXX windows API
- Unit tests for the implementation and for the previous CL that
  had the sine wave simple source.

This is the harder one :) I tried to add comments to illuminate the thinking.


Review URL: http://codereview.chromium.org/17403

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@7988 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 106 insertions, 0 deletions

diff --git a/media/audio/win/waveout_output_win.h b/media/audio/win/waveout_output_win.h
new file mode 100644
index 0000000..bdf35b3
--- /dev/null
+++ b/media/audio/win/waveout_output_win.h
@@ -0,0 +1,106 @@
+// 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.
+
+#ifndef MEDIA_AUDIO_WAVEOUT_OUTPUT_WIN_H_
+#define MEDIA_AUDIO_WAVEOUT_OUTPUT_WIN_H_
+
+#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 {
+ 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,
+                              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);
+
+ private:
+  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.
+  WAVEFORMATEX format_;
+
+  // 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_;
+
+  DISALLOW_COPY_AND_ASSIGN(PCMWaveOutAudioOutputStream);
+};
+
+#endif  // MEDIA_AUDIO_WAVEOUT_OUTPUT_WIN_H_
+