From 36843ab0abc7239d0fc2eaa6fea2a85d357f6dba Mon Sep 17 00:00:00 2001
From: "nfullagar@google.com"
<nfullagar@google.com@0039d316-1c4b-4281-b951-d872f2087c98>
Date: Tue, 11 Jan 2011 22:02:38 +0000
Subject: [PATCH] Make audio example up-to-date BUG=none TEST=none
Review URL: http://codereview.chromium.org/6135007
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@71095 0039d316-1c4b-4281-b951-d872f2087c98
---
ppapi/examples/audio/audio.cc | 49 ++++++++++++++++++++++-------------
1 file changed, 31 insertions(+), 18 deletions(-)
diff --git a/ppapi/examples/audio/audio.cc b/ppapi/examples/audio/audio.cc
index fcef2b194abdb..a0ba06748ba99 100644
--- a/ppapi/examples/audio/audio.cc
+++ b/ppapi/examples/audio/audio.cc
@@ -12,7 +12,7 @@
// Separate left and right frequency to make sure we didn't swap L & R.
// Sounds pretty horrible, though...
-const double frequency_l = 200;
+const double frequency_l = 400;
const double frequency_r = 1000;
// This sample frequency is guaranteed to work.
@@ -20,46 +20,59 @@ const PP_AudioSampleRate_Dev sample_frequency = PP_AUDIOSAMPLERATE_44100;
const uint32_t sample_count = 4096;
uint32_t obtained_sample_count = 0;
+const double kPi = 3.141592653589;
+const double kTwoPi = 2.0 * kPi;
+
class MyInstance : public pp::Instance {
public:
explicit MyInstance(PP_Instance instance)
: pp::Instance(instance),
- audio_time_(0) {
+ audio_wave_l_(0.0),
+ audio_wave_r_(0.0) {
}
virtual bool Init(uint32_t argc, const char* argn[], const char* argv[]) {
pp::AudioConfig_Dev config;
obtained_sample_count = pp::AudioConfig_Dev::RecommendSampleFrameCount(
sample_count);
- config = pp::AudioConfig_Dev(sample_frequency, obtained_sample_count);
- audio_ = pp::Audio_Dev(*this, config, SineWaveCallback, this);
+ config = pp::AudioConfig_Dev(this, sample_frequency, obtained_sample_count);
+ audio_ = pp::Audio_Dev(this, config, SineWaveCallback, this);
return audio_.StartPlayback();
}
private:
static void SineWaveCallback(void* samples, size_t num_bytes, void* thiz) {
- const double th_l = 2 * 3.141592653589 * frequency_l / sample_frequency;
- const double th_r = 2 * 3.141592653589 * frequency_r / sample_frequency;
-
- // Store time value to avoid clicks on buffer boundries.
- size_t t = reinterpret_cast<MyInstance*>(thiz)->audio_time_;
+ const double delta_l = kTwoPi * frequency_l / sample_frequency;
+ const double delta_r = kTwoPi * frequency_r / sample_frequency;
- uint16_t* buf = reinterpret_cast<uint16_t*>(samples);
+ // Use per channel audio wave value to avoid clicks on buffer boundries.
+ double wave_l = reinterpret_cast<MyInstance*>(thiz)->audio_wave_l_;
+ double wave_r = reinterpret_cast<MyInstance*>(thiz)->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 < obtained_sample_count; ++sample) {
- *buf++ = static_cast<uint16_t>(sin(th_l * t)
- * std::numeric_limits<uint16_t>::max());
- *buf++ = static_cast<uint16_t>(sin(th_r * t++)
- * std::numeric_limits<uint16_t>::max());
+ *buf++ = static_cast<int16_t>(sin(wave_l) * max_int16);
+ *buf++ = static_cast<int16_t>(sin(wave_r) * max_int16);
+ // Add delta, keep within -kTwoPi..kTwoPi to preserve precision.
+ wave_l += delta_l;
+ if (wave_l > kTwoPi)
+ wave_l -= kTwoPi * 2.0;
+ wave_r += delta_r;
+ if (wave_r > kTwoPi)
+ wave_r -= kTwoPi * 2.0;
}
- reinterpret_cast<MyInstance*>(thiz)->audio_time_ = t;
+ // Store current value to use as starting point for next callback.
+ reinterpret_cast<MyInstance*>(thiz)->audio_wave_l_ = wave_l;
+ reinterpret_cast<MyInstance*>(thiz)->audio_wave_r_ = wave_r;
}
// Audio resource. Allocated in Init(), freed on destruction.
pp::Audio_Dev audio_;
- // Audio buffer time. Used to make prevent sine wave skips on buffer
- // boundaries.
- size_t audio_time_;
+ // 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 {
--
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