FroM： http://uberblo.gs/2011/04/iosiphoneos-equalizer-with-libsox-doing-effects
Today i will show you how to do sound effects from within iOS using libsox.
It is pretty straight forward, the code is here:
#import "sox.h"
-
(
NSString
*
)
transformAudioFileAtPath:
(
NSString
*
)
path
profile:
(
int
)
tprofile
{
static
sox_format_t
*
in
,
*
out
;
/* input and output files */
sox_effects_chain_t
*
chain
;
sox_effect_t
*
e
;
char
*
args
[
10
];
NSString
*
target
=
[
path
stringByReplacingOccurrencesOfString:
@".0.wav"
withString:
[
NSString
stringWithFormat:
@".%i.wav"
,
tprofile
]];
target
=
[
target
stringByReplacingOccurrencesOfString:
@"Hoersimulator.app"
withString:
@"Documents"
];
[
target
retain
];
if
([[
NSFileManager
alloc
]
fileExistsAtPath:
target
])
return
target
;
/* All libSoX applications must start by initialising the SoX library */
assert
(
sox_init
()
==
SOX_SUCCESS
);
/* Open the input file (with default parameters) */
assert
(
in
=
sox_open_read
([
path
UTF8String
],
NULL
,
NULL
,
NULL
));
/* Open the output file; we must specify the output signal characteristics.
* Since we are using only simple effects, they are the same as the input
* file characteristics */
assert
(
out
=
sox_open_write
([
target
UTF8String
],
&
in
->
signal
,
NULL
,
NULL
,
NULL
,
NULL
));
/* Create an effects chain; some effects need to know about the input
* or output file encoding so we provide that information here */
chain
=
sox_create_effects_chain
(
&
in
->
encoding
,
&
out
->
encoding
);
/* The first effect in the effect chain must be something that can source
* samples; in this case, we use the built-in handler that inputs
* data from an audio file */
e
=
sox_create_effect
(
sox_find_effect
(
"input"
));
args
[
0
]
=
(
char
*
)
in
,
assert
(
sox_effect_options
(
e
,
1
,
args
)
==
SOX_SUCCESS
);
/* This becomes the first `effect' in the chain */
assert
(
sox_add_effect
(
chain
,
e
,
&
in
->
signal
,
&
in
->
signal
)
==
SOX_SUCCESS
);
if
(
tprofile
==
1
)
{
e
=
sox_create_effect
(
sox_find_effect
(
"lowpass"
));
args
[
0
]
=
"2000"
,
assert
(
sox_effect_options
(
e
,
1
,
args
)
==
SOX_SUCCESS
);
assert
(
sox_add_effect
(
chain
,
e
,
&
in
->
signal
,
&
in
->
signal
)
==
SOX_SUCCESS
);
e
=
sox_create_effect
(
sox_find_effect
(
"gain"
));
args
[
0
]
=
"-10"
,
assert
(
sox_effect_options
(
e
,
1
,
args
)
==
SOX_SUCCESS
);
assert
(
sox_add_effect
(
chain
,
e
,
&
in
->
signal
,
&
in
->
signal
)
==
SOX_SUCCESS
);
}
if
(
tprofile
==
2
)
{
e
=
sox_create_effect
(
sox_find_effect
(
"lowpass"
));
args
[
0
]
=
"1000"
,
assert
(
sox_effect_options
(
e
,
1
,
args
)
==
SOX_SUCCESS
);
assert
(
sox_add_effect
(
chain
,
e
,
&
in
->
signal
,
&
in
->
signal
)
==
SOX_SUCCESS
);
e
=
sox_create_effect
(
sox_find_effect
(
"gain"
));
args
[
0
]
=
"-25"
,
assert
(
sox_effect_options
(
e
,
1
,
args
)
==
SOX_SUCCESS
);
assert
(
sox_add_effect
(
chain
,
e
,
&
in
->
signal
,
&
in
->
signal
)
==
SOX_SUCCESS
);
}
/* Create the `vol' effect, and initialise it with the desired parameters: */
e
=
sox_create_effect
(
sox_find_effect
(
"vol"
));
args
[
0
]
=
"3dB"
,
assert
(
sox_effect_options
(
e
,
1
,
args
)
==
SOX_SUCCESS
);
/* Add the effect to the end of the effects processing chain: */
assert
(
sox_add_effect
(
chain
,
e
,
&
in
->
signal
,
&
in
->
signal
)
==
SOX_SUCCESS
);
/* Create the `flanger' effect, and initialise it with default parameters: */
e
=
sox_create_effect
(
sox_find_effect
(
"flanger"
));
assert
(
sox_effect_options
(
e
,
0
,
NULL
)
==
SOX_SUCCESS
);
/* Add the effect to the end of the effects processing chain: */
assert
(
sox_add_effect
(
chain
,
e
,
&
in
->
signal
,
&
in
->
signal
)
==
SOX_SUCCESS
);
/* The last effect in the effect chain must be something that only consumes
* samples; in this case, we use the built-in handler that outputs
* data to an audio file */
e
=
sox_create_effect
(
sox_find_effect
(
"output"
));
args
[
0
]
=
(
char
*
)
out
,
assert
(
sox_effect_options
(
e
,
1
,
args
)
==
SOX_SUCCESS
);
assert
(
sox_add_effect
(
chain
,
e
,
&
in
->
signal
,
&
in
->
signal
)
==
SOX_SUCCESS
);
/* Flow samples through the effects processing chain until EOF is reached */
sox_flow_effects
(
chain
,
NULL
,
NULL
);
/* All done; tidy up: */
sox_delete_effects_chain
(
chain
);
sox_close
(
out
);
sox_close
(
in
);
sox_quit
();
return
target
;
}
I've added a variable (int)tprofile which can be used for different effects without having to rewrite or copy everything. Simply apply your effects in an if-clause and be the king of the hill! At least know i am! :)
best regards fellow Apple survivors