A simple tone source useful for testing and troubleshooting

- Only windows 16 PCM mono implementation so far.

Review URL: http://codereview.chromium.org/16226

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@7557 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 83 insertions, 0 deletions

diff --git a/media/audio/simple_sources.h b/media/audio/simple_sources.h
new file mode 100644
index 0000000..992aba5
--- /dev/null
+++ b/media/audio/simple_sources.h
@@ -0,0 +1,40 @@
+// 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_SIMPLE_SOURCES_H_
+#define MEDIA_AUDIO_SIMPLE_SOURCES_H_
+
+#include "media/audio/audio_output.h"
+
+// An audio source that produces a pure sinusoidal tone. Each platform needs
+// a slightly different implementation because it needs to handle the native
+// audio buffer format.
+class SineWaveAudioSource : public AudioOutputStream::AudioSourceCallback {
+ public:
+  enum Format {
+    FORMAT_8BIT_LINEAR_PCM,
+    FORMAT_16BIT_LINEAR_PCM,
+  };
+
+  // |channels| is the number of audio channels, |freq| is the frequency in
+  // hertz and it has to be less than half of the sampling frequency
+  // |sample_freq| or else you will get aliasing.
+  SineWaveAudioSource(Format format, int channels,
+                      double freq, double sample_freq);
+  virtual ~SineWaveAudioSource() {}
+
+  // Implementation of AudioSourceCallback.
+  virtual size_t OnMoreData(AudioOutputStream* stream,
+                            void* dest, size_t max_size);
+  virtual void OnClose(AudioOutputStream* stream);
+  virtual void OnError(AudioOutputStream* stream, int code);
+
+ protected:
+  Format format_;
+  int channels_;
+  double freq_;
+  double sample_freq_;
+};
+
+#endif  // MEDIA_AUDIO_SIMPLE_SOURCES_H_
diff --git a/media/audio/win/simple_sources_win.cc b/media/audio/win/simple_sources_win.cc
new file mode 100644
index 0000000..b6fda23
--- /dev/null
+++ b/media/audio/win/simple_sources_win.cc
@@ -0,0 +1,43 @@
+// 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 <math.h>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "media/audio/audio_output.h"
+#include "media/audio/simple_sources.h"
+
+SineWaveAudioSource::SineWaveAudioSource(Format format, int channels,
+                                         double freq, double sample_freq)
+    : format_(format),
+      channels_(channels),
+      freq_(freq),
+      sample_freq_(sample_freq) {
+  // TODO(cpu): support other formats.
+  DCHECK((format_ == FORMAT_16BIT_LINEAR_PCM) && (channels_ == 1));
+}
+
+// The implementation could be more efficient if a lookup table is constructed
+// but it is efficient enough for our simple needs.
+size_t SineWaveAudioSource::OnMoreData(AudioOutputStream* stream,
+                                       void* dest, size_t max_size) {
+  const double kTwoPi = 2.0 * 3.141592653589;
+  double f = freq_ / sample_freq_;
+  int16* sin_tbl = reinterpret_cast<int16*>(dest);
+  size_t len = max_size / sizeof(int16);
+  // The table is filled with s(t) = 32768*sin(2PI*f*t).
+  for (size_t ix = 0; ix != len; ++ix) {
+    double th = kTwoPi * ix * f;
+    sin_tbl[ix] = static_cast<int16>((1 << 15) * sin(th));
+  }
+  return max_size;
+}
+
+void SineWaveAudioSource::OnClose(AudioOutputStream* stream) {
+}
+
+void SineWaveAudioSource::OnError(AudioOutputStream* stream, int code) {
+  NOTREACHED();
+}