/[pcsx2_0.9.7]/trunk/3rdparty/portaudio/src/common/pa_dither.h
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Contents of /trunk/3rdparty/portaudio/src/common/pa_dither.h

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Revision 10 - (show annotations) (download)
Mon Sep 6 11:40:06 2010 UTC (9 years, 11 months ago) by william
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exported r3113 from ./upstream/trunk
1 #ifndef PA_DITHER_H
2 #define PA_DITHER_H
3 /*
4 * $Id: pa_dither.h 1418 2009-10-12 21:00:53Z philburk $
5 * Portable Audio I/O Library triangular dither generator
6 *
7 * Based on the Open Source API proposed by Ross Bencina
8 * Copyright (c) 1999-2002 Phil Burk, Ross Bencina
9 *
10 * Permission is hereby granted, free of charge, to any person obtaining
11 * a copy of this software and associated documentation files
12 * (the "Software"), to deal in the Software without restriction,
13 * including without limitation the rights to use, copy, modify, merge,
14 * publish, distribute, sublicense, and/or sell copies of the Software,
15 * and to permit persons to whom the Software is furnished to do so,
16 * subject to the following conditions:
17 *
18 * The above copyright notice and this permission notice shall be
19 * included in all copies or substantial portions of the Software.
20 *
21 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
22 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
23 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
24 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
25 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
26 * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
27 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
28 */
29
30 /*
31 * The text above constitutes the entire PortAudio license; however,
32 * the PortAudio community also makes the following non-binding requests:
33 *
34 * Any person wishing to distribute modifications to the Software is
35 * requested to send the modifications to the original developer so that
36 * they can be incorporated into the canonical version. It is also
37 * requested that these non-binding requests be included along with the
38 * license above.
39 */
40
41 /** @file
42 @ingroup common_src
43
44 @brief Functions for generating dither noise
45 */
46
47 #include "pa_types.h"
48
49
50 #ifdef __cplusplus
51 extern "C"
52 {
53 #endif /* __cplusplus */
54
55 /* Note that the linear congruential algorithm requires 32 bit integers
56 * because it uses arithmetic overflow. So use PaUint32 instead of
57 * unsigned long so it will work on 64 bit systems.
58 */
59
60 /** @brief State needed to generate a dither signal */
61 typedef struct PaUtilTriangularDitherGenerator{
62 PaUint32 previous;
63 PaUint32 randSeed1;
64 PaUint32 randSeed2;
65 } PaUtilTriangularDitherGenerator;
66
67
68 /** @brief Initialize dither state */
69 void PaUtil_InitializeTriangularDitherState( PaUtilTriangularDitherGenerator *ditherState );
70
71
72 /**
73 @brief Calculate 2 LSB dither signal with a triangular distribution.
74 Ranged for adding to a 1 bit right-shifted 32 bit integer
75 prior to >>15. eg:
76 <pre>
77 signed long in = *
78 signed long dither = PaUtil_Generate16BitTriangularDither( ditherState );
79 signed short out = (signed short)(((in>>1) + dither) >> 15);
80 </pre>
81 @return
82 A signed 32-bit integer with a range of +32767 to -32768
83 */
84 PaInt32 PaUtil_Generate16BitTriangularDither( PaUtilTriangularDitherGenerator *ditherState );
85
86
87 /**
88 @brief Calculate 2 LSB dither signal with a triangular distribution.
89 Ranged for adding to a pre-scaled float.
90 <pre>
91 float in = *
92 float dither = PaUtil_GenerateFloatTriangularDither( ditherState );
93 // use smaller scaler to prevent overflow when we add the dither
94 signed short out = (signed short)(in*(32766.0f) + dither );
95 </pre>
96 @return
97 A float with a range of -2.0 to +1.99999.
98 */
99 float PaUtil_GenerateFloatTriangularDither( PaUtilTriangularDitherGenerator *ditherState );
100
101
102
103 #ifdef __cplusplus
104 }
105 #endif /* __cplusplus */
106 #endif /* PA_DITHER_H */

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