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

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Revision 10 - (hide annotations) (download)
Mon Sep 6 11:40:06 2010 UTC (10 years ago) by william
File MIME type: text/plain
File size: 3685 byte(s)
exported r3113 from ./upstream/trunk
1 william 10 #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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