c-使用libsox在不改变节奏的情况下更改音频文件音高

Question

我开发了一个简单的应用程序，可以使用libsox更改音频文件的音高(使用本例(。这是我的密码。它使用2个输入参数-输入文件路径&输出文件路径：

#include <sox.h>
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <string.h>
int main(int argc, char * argv[])
{
static sox_format_t * in, * out; /* input and output files */
sox_effects_chain_t * chain;
sox_effect_t * e;
char * args[10];
sox_signalinfo_t interm_signal; /* @ intermediate points in the chain. */
sox_encodinginfo_t out_encoding = {
SOX_ENCODING_SIGN2,
16,
0,
sox_option_default,
sox_option_default,
sox_option_default,
sox_false
};
sox_signalinfo_t out_signal = {
16000,
1,
0,
0,
NULL
};
assert(argc == 3);
assert(sox_init() == SOX_SUCCESS);
assert(in = sox_open_read(argv[1], NULL, NULL, NULL));
assert(out = sox_open_write(argv[2], &out_signal, &out_encoding, NULL, NULL, NULL));
chain = sox_create_effects_chain(&in->encoding, &out->encoding);
interm_signal = in->signal; /* NB: deep copy */
e = sox_create_effect(sox_find_effect("input"));
args[0] = (char *)in; 
assert(sox_effect_options(e, 1, args) == SOX_SUCCESS);
assert(sox_add_effect(chain, e, &interm_signal, &in->signal) == SOX_SUCCESS);
free(e);
e = sox_create_effect(sox_find_effect("pitch"));
args[0] = "1000";
assert(sox_effect_options(e, 1, args) == SOX_SUCCESS);
assert(sox_add_effect(chain, e, &interm_signal, &out->signal) == SOX_SUCCESS);
free(e);
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, &interm_signal, &out->signal) == SOX_SUCCESS);
free(e);
sox_flow_effects(chain, NULL, NULL);
sox_delete_effects_chain(chain);
sox_close(out);
sox_close(in);
sox_quit();
return 0;
}

但我从上面的代码中得到的结果是一个节奏发生了变化的文件。以下是输入和输出的详细信息：

Input File     : 'input.wav'
Channels       : 1
Sample Rate    : 16000
Precision      : 16-bit
Duration       : 00:00:11.87 = 189921 samples ~ 890.255 CDDA sectors
Input File     : 'output.wav'
Channels       : 1
Sample Rate    : 16000
Precision      : 16-bit
Duration       : 00:00:21.15 = 338401 samples ~ 1586.25 CDDA sectors

另外，sox应用程序运行良好。

sox input.wav output_app.wav pitch 1000

它生成一个与输入持续时间相同的文件：

Input File     : 'output_app.wav'
Channels       : 1
Sample Rate    : 16000
Precision      : 16-bit
Duration       : 00:00:11.87 = 189921 samples ~ 890.255 CDDA sectors

这里有人有同样的问题吗？或者，我是否必须向sox_effect提供任何其他选项才能使这种效果正常工作？

Answer 1

libsox的"pitch"效果将改变音频采样率。如果你注意到"pitch"之后的采样率，你会发现它已经改变了。为了以相同的采样率保存音频文件，您需要在"音高"效果之后添加"速率"效果。像这样：

#include <sox.h>
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <string.h>
int main(int argc, char * argv[])
{
static sox_format_t * in, * out; /* input and output files */
sox_effects_chain_t * chain;
sox_effect_t * e;
char * args[10];
sox_signalinfo_t interm_signal; /* @ intermediate points in the chain. */
sox_encodinginfo_t out_encoding = {
SOX_ENCODING_SIGN2,
16,
0,
sox_option_default,
sox_option_default,
sox_option_default,
sox_false
};
sox_signalinfo_t out_signal = {
16000,
1,
0,
0,
NULL
};
assert(argc == 3);
assert(sox_init() == SOX_SUCCESS);
assert(in = sox_open_read(argv[1], NULL, NULL, NULL));
assert(out = sox_open_write(argv[2], &out_signal, &out_encoding, NULL, NULL, NULL));
chain = sox_create_effects_chain(&in->encoding, &out->encoding);
interm_signal = in->signal; /* NB: deep copy */
e = sox_create_effect(sox_find_effect("input"));
args[0] = (char *)in; 
assert(sox_effect_options(e, 1, args) == SOX_SUCCESS);
assert(sox_add_effect(chain, e, &interm_signal, &in->signal) == SOX_SUCCESS);
free(e);
e = sox_create_effect(sox_find_effect("pitch"));
args[0] = "1000";
assert(sox_effect_options(e, 1, args) == SOX_SUCCESS);
assert(sox_add_effect(chain, e, &interm_signal, &out->signal) == SOX_SUCCESS);
free(e);
// Note: interm_signal.rate changed now, we need to rate it back
e = sox_create_effect(sox_find_effect("rate"));
args[0] = "-m";
assert(sox_effect_options(e, 1, args) == SOX_SUCCESS);
assert(sox_add_effect(chain, e, &interm_signal, &out->signal) == SOX_SUCCESS);
free(e);
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, &interm_signal, &out->signal) == SOX_SUCCESS);
free(e);
sox_flow_effects(chain, NULL, NULL);
sox_delete_effects_chain(chain);
sox_close(out);
sox_close(in);
sox_quit();
return 0;
}

或者，您可以在"速率"之后添加"抖动"效果，以获得更好的结果。

Answer 2

搜索了一段时间后，感谢您。我发现，为了保持音频节奏，必须在音高效果之后的效果链中添加速率效果