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// Copyright (c) 2012 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.
// Needed on Windows to get |M_PI| from math.h.
#ifdef _WIN32
#define _USE_MATH_DEFINES
#endif
#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <limits>
#include "ppapi/c/pp_errors.h"
#include "ppapi/cpp/audio.h"
#include "ppapi/cpp/audio_config.h"
#include "ppapi/cpp/completion_callback.h"
#include "ppapi/cpp/instance.h"
#include "ppapi/cpp/module.h"
#include "ppapi/cpp/view.h"
// Separate left and right frequency to make sure we didn't swap L & R.
// Sounds pretty horrible, though...
const double kLeftFrequency = 400;
const double kRightFrequency = 1000;
// This sample frequency is guaranteed to work.
const PP_AudioSampleRate kDefaultSampleRate = PP_AUDIOSAMPLERATE_44100;
const uint32_t kDefaultSampleCount = 4096;
const char kSampleRateAttributeName[] = "samplerate";
class MyInstance : public pp::Instance {
public:
explicit MyInstance(PP_Instance instance)
: pp::Instance(instance),
visible_(false),
sample_rate_(kDefaultSampleRate),
sample_count_(0),
audio_wave_l_(0.0),
audio_wave_r_(0.0) {
}
virtual bool Init(uint32_t argc, const char* argn[], const char* argv[]) {
for (uint32_t i = 0; i < argc; i++) {
if (strcmp(kSampleRateAttributeName, argn[i]) == 0) {
int value = atoi(argv[i]);
if (value > 0 && value <= 1000000)
sample_rate_ = static_cast<PP_AudioSampleRate>(value);
else
return false;
}
}
pp::AudioConfig config;
sample_count_ = pp::AudioConfig::RecommendSampleFrameCount(
this, sample_rate_, kDefaultSampleCount);
config = pp::AudioConfig(this, sample_rate_, sample_count_);
audio_ = pp::Audio(this, config, SineWaveCallbackTrampoline, this);
return audio_.StartPlayback();
}
virtual void DidChangeView(const pp::View& view) {
// The frequency will change depending on whether the page is in the
// foreground or background.
visible_ = view.IsPageVisible();
}
private:
static void SineWaveCallbackTrampoline(void* samples,
uint32_t num_bytes,
void* thiz) {
static_cast<MyInstance*>(thiz)->SineWaveCallback(samples, num_bytes);
}
void SineWaveCallback(void* samples, uint32_t num_bytes) {
double delta_l = 2.0 * M_PI * kLeftFrequency / sample_rate_ /
(visible_ ? 1 : 2);
double delta_r = 2.0 * M_PI * kRightFrequency / sample_rate_ /
(visible_ ? 1 : 2);
// Use per channel audio wave value to avoid clicks on buffer boundries.
double wave_l = audio_wave_l_;
double wave_r = audio_wave_r_;
const int16_t max_int16 = std::numeric_limits<int16_t>::max();
int16_t* buf = reinterpret_cast<int16_t*>(samples);
for (size_t sample = 0; sample < sample_count_; ++sample) {
*buf++ = static_cast<int16_t>(sin(wave_l) * max_int16);
*buf++ = static_cast<int16_t>(sin(wave_r) * max_int16);
// Add delta, keep within -2 * M_PI .. 2 * M_PI to preserve precision.
wave_l += delta_l;
if (wave_l > 2.0 * M_PI)
wave_l -= 2.0 * M_PI;
wave_r += delta_r;
if (wave_r > 2.0 * M_PI)
wave_r -= 2.0 * M_PI;
}
// Store current value to use as starting point for next callback.
audio_wave_l_ = wave_l;
audio_wave_r_ = wave_r;
}
bool visible_;
PP_AudioSampleRate sample_rate_;
uint32_t sample_count_;
pp::Audio audio_;
// Current audio wave position, used to prevent sine wave skips
// on buffer boundaries.
double audio_wave_l_;
double audio_wave_r_;
};
class MyModule : public pp::Module {
public:
// Override CreateInstance to create your customized Instance object.
virtual pp::Instance* CreateInstance(PP_Instance instance) {
return new MyInstance(instance);
}
};
namespace pp {
// Factory function for your specialization of the Module object.
Module* CreateModule() {
return new MyModule();
}
} // namespace pp
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