Extending supported sample rate from 3.0KHz to 192.0KHz for OfflineAudioContext.

Source/platform/audio/HRTFPanner.cpp

Index: Source/platform/audio/HRTFPanner.cpp
diff --git a/Source/platform/audio/HRTFPanner.cpp b/Source/platform/audio/HRTFPanner.cpp
index 04e410dba233decde70c91472d12cf7ba6103ab3..7309d0049a622086469d406f61052a967a0f9bdd 100644
--- a/Source/platform/audio/HRTFPanner.cpp
+++ b/Source/platform/audio/HRTFPanner.cpp
@@ -45,6 +45,11 @@ const double MaxDelayTimeSeconds = 0.002;
 const int UninitializedAzimuth = -1;
 const unsigned RenderingQuantum = 128;
 
+// Support sample rate from 3 kHz to 192 kHz.

[Raymond Toy, 2014/09/04 17:27:20]

This comment seems unrelated to the following code. Update it to match the code.
You probably want to explain why 32 and 4096 are appropriate limits on the fft
size.

[KhNo, 2014/09/05 05:03:25]

I changed logic to find correct fft size. Do not need more this magic values.

+const size_t minfftSize = 32;
+const size_t maxfftSize = 4096;
+const float coefficientSampleRate = 2756.25f;

[Raymond Toy, 2014/09/04 17:27:20]

No trialing "f" required according to blink style.

You probably explained this to me, but where does the 2765.25 come from? You'll
probably need to add a comment to say where this magic number comes from.

[KhNo, 2014/09/05 05:03:25]

Done.

+
 HRTFPanner::HRTFPanner(float sampleRate, HRTFDatabaseLoader* databaseLoader)
     : Panner(PanningModelHRTF)
     , m_databaseLoader(databaseLoader)
@@ -79,8 +84,15 @@ size_t HRTFPanner::fftSizeForSampleRate(float sampleRate)
     // The HRTF impulse responses (loaded as audio resources) are 512 sample-frames @44.1KHz.
     // Currently, we truncate the impulse responses to half this size, but an FFT-size of twice impulse response size is needed (for convolution).
     // So for sample rates around 44.1KHz an FFT size of 512 is good. We double the FFT-size only for sample rates at least double this.
-    ASSERT(sampleRate >= 44100 && sampleRate <= 96000.0);
-    return (sampleRate < 88200.0) ? 512 : 1024;
+    ASSERT(sampleRate >= 3000.f && sampleRate <= 192000.f);

[Raymond Toy, 2014/09/04 17:27:20]

No ".f" allowed per blink style guide.

[KhNo, 2014/09/05 05:03:25]

Done.

+
+    if (sampleRate < 3000.f)
+        return minfftSize;
+    if (sampleRate > 192000.f)
+        return maxfftSize;
+
+    int scale = floor(sampleRate / coefficientSampleRate);
+    return scale * minfftSize;

[Raymond Toy, 2014/09/04 17:27:20]

Don't you need to make sure the returned FFT size is a power of two?

[KhNo, 2014/09/05 05:03:25]

Yes, it is required. I think I missed it during update patch set.
I changed the logic to find correct fft size from array that is guaranteed power
of two.
Thanks for detailed checking.

 }
 
 void HRTFPanner::reset()