Changeset 102733 in webkit

Timestamp:

Dec 13, 2011 8:56:56 PM (12 years ago)

Author:

commit-queue@webkit.org

Message:

Optimize to not use pow() in the inner loop in AudioParamTimeline
​https://bugs.webkit.org/show_bug.cgi?id=73530

Patch by James Wei <​james.wei@intel.com> on 2011-12-13
Reviewed by Kenneth Russell.

No new tests.

• webaudio/AudioParamTimeline.cpp:

(WebCore:AudioParamTimeline:valuesForTimeRangeImpl):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• webaudio/AudioParamTimeline.cpp (modified) (1 diff)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2011-12-13  James Wei <james.wei@intel.com> 
+
+        Optimize to not use pow() in the inner loop in AudioParamTimeline
+        https://bugs.webkit.org/show_bug.cgi?id=73530
+
+        Reviewed by Kenneth Russell.
+
+        No new tests.
+
+        * webaudio/AudioParamTimeline.cpp:
+        (WebCore:AudioParamTimeline:valuesForTimeRangeImpl):
+
 2011-12-13  Hajime Morrita  <morrita@chromium.org>
 

trunk/Source/WebCore/webaudio/AudioParamTimeline.cpp

@@ -246 +246 @@
                     values[writeIndex] = value;
             } else {
-                // Interpolate in log space.
-                value1 = log2f(value1);
-                value2 = log2f(value2);
-
-                // FIXME: optimize to not use pow() in inner loop, this is just a simple exponential ramp.
+                float numSampleFrames = deltaTime * sampleRate;
+                // The value goes exponentially from value1 to value2 in a duration of deltaTime seconds (corresponding to numSampleFrames).
+                // Compute the per-sample multiplier.
+                float multiplier = powf(value2 / value1, 1 / numSampleFrames);
                 for (; writeIndex < fillToFrame; ++writeIndex) {
-                    float x = (currentTime - time1) * k;
-                    value = (1 - x) * value1 + x * value2;
-                    value = powf(2.0f, value);
                     values[writeIndex] = value;
+                    value *= multiplier;
                     currentTime += sampleFrameTimeIncr;
                 }