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1 /*
2  * Copyright (C) 2011 Google Inc. All rights reserved.
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1.  Redistributions of source code must retain the above copyright
9  *     notice, this list of conditions and the following disclaimer.
10  * 2.  Redistributions in binary form must reproduce the above copyright
11  *     notice, this list of conditions and the following disclaimer in the
12  *     documentation and/or other materials provided with the distribution.
13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
14  *     its contributors may be used to endorse or promote products derived
15  *     from this software without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27  */
28 
29 #include "config.h"
30 
31 #if ENABLE(WEB_AUDIO)
32 
33 #include "platform/audio/ZeroPole.h"
34 
35 #include "platform/audio/DenormalDisabler.h"
36 
37 namespace blink {
38 
process(const float * source,float * destination,unsigned framesToProcess)39 void ZeroPole::process(const float *source, float *destination, unsigned framesToProcess)
40 {
41     float zero = m_zero;
42     float pole = m_pole;
43 
44     // Gain compensation to make 0dB @ 0Hz
45     const float k1 = 1 / (1 - zero);
46     const float k2 = 1 - pole;
47 
48     // Member variables to locals.
49     float lastX = m_lastX;
50     float lastY = m_lastY;
51 
52     while (framesToProcess--) {
53         float input = *source++;
54 
55         // Zero
56         float output1 = k1 * (input - zero * lastX);
57         lastX = input;
58 
59         // Pole
60         float output2 = k2 * output1 + pole * lastY;
61         lastY = output2;
62 
63         *destination++ = output2;
64     }
65 
66     // Locals to member variables. Flush denormals here so we don't
67     // slow down the inner loop above.
68     m_lastX = DenormalDisabler::flushDenormalFloatToZero(lastX);
69     m_lastY = DenormalDisabler::flushDenormalFloatToZero(lastY);
70 }
71 
72 } // namespace blink
73 
74 #endif // ENABLE(WEB_AUDIO)
75