blob: ae4c69dda9214e9de80bbd2b6a2da402e28a871d (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
|
/*----------------------------------------------------------------------------
*
* File:
* eas_pan.c
*
* Contents and purpose:
* Calculates left and right gain multipliers based on a pan value from -63 to +63
*
* NOTES:
* The _CMX_PARSER and _MFI_PARSER preprocessor symbols determine
* whether the parser works for those particular file formats.
*
* Copyright Sonic Network Inc. 2005
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*----------------------------------------------------------------------------
* Revision Control:
* $Revision: 82 $
* $Date: 2006-07-10 11:45:19 -0700 (Mon, 10 Jul 2006) $
*----------------------------------------------------------------------------
*/
#include "eas_pan.h"
#include "eas_math.h"
/*----------------------------------------------------------------------------
* EAS_CalcPanControl()
*----------------------------------------------------------------------------
* Purpose:
* Assign the left and right gain values corresponding to the given pan value.
*
* This routine uses sin/cos approximations for an equal power curve:
*
* sin(x) = (2-4*c)*x^2 + c + x
* cos(x) = (2-4*c)*x^2 + c - x
*
* where c = 1/sqrt(2)
* using the a0 + x*(a1 + x*a2) approach
*
* Inputs:
* pan - pan value (-63 to + 63)
*
* Outputs:
* pGainLeft linear gain multiplier for left channel (15-bit fraction)
* pGainRight linear gain multiplier for left channel (15-bit fraction)
*
* Side Effects:
*----------------------------------------------------------------------------
*/
void EAS_CalcPanControl (EAS_INT pan, EAS_I16 *pGainLeft, EAS_I16 *pGainRight)
{
EAS_INT temp;
EAS_INT netAngle;
/* impose hard limit */
if (pan < -63)
netAngle = -63;
else if (pan > 63)
netAngle = 63;
else
netAngle = pan;
/*lint -e{701} <avoid multiply for performance reasons>*/
netAngle = netAngle << 8;
/* calculate sin */
temp = EG1_ONE + FMUL_15x15(COEFF_PAN_G2, netAngle);
temp = COEFF_PAN_G0 + FMUL_15x15(temp, netAngle);
if (temp > SYNTH_FULL_SCALE_EG1_GAIN)
temp = SYNTH_FULL_SCALE_EG1_GAIN;
else if (temp < 0)
temp = 0;
*pGainRight = (EAS_I16) temp;
/* calculate cos */
temp = -EG1_ONE + FMUL_15x15(COEFF_PAN_G2, netAngle);
temp = COEFF_PAN_G0 + FMUL_15x15(temp, netAngle);
if (temp > SYNTH_FULL_SCALE_EG1_GAIN)
temp = SYNTH_FULL_SCALE_EG1_GAIN;
else if (temp < 0)
temp = 0;
*pGainLeft = (EAS_I16) temp;
}
|
