您可以实现您的项目作为一个LADSPA插件的,与audacity
或任何其他程序支持LADSPA插件测试它,当你喜欢它,把它插入到ALSA /的PulseAudio /插孔播放链。
“LADSPA”是一个single header file定义了一个简单的接口来编写音频处理插件。每个插件都有其输入/输出/控制端口和run()
功能。对每个采样块执行run()
函数以进行实际的音频处理 - 将“控制”参数应用于“输入”缓冲区并将结果写入“输出”缓冲区。
例LADSPA立体声放大器插件(单个控制参数:“扩增因子”,两个输入端口,两个输出端口):
///gcc -shared -o /full/path/to/plugindir/amp_example.so amp_example.c
#include <stdlib.h>
#include "ladspa.h"
enum PORTS {
PORT_CAMP,
PORT_INPUT1,
PORT_INPUT2,
PORT_OUTPUT1,
PORT_OUTPUT2
};
typedef struct {
LADSPA_Data *c_amp;
LADSPA_Data *i_audio1;
LADSPA_Data *i_audio2;
LADSPA_Data *o_audio1;
LADSPA_Data *o_audio2;
} MyAmpData;
static LADSPA_Handle myamp_instantiate(const LADSPA_Descriptor *Descriptor, unsigned long SampleRate)
{
MyAmpData *data = (MyAmpData*)malloc(sizeof(MyAmpData));
data->c_amp = NULL;
data->i_audio1 = NULL;
data->i_audio2 = NULL;
data->o_audio1 = NULL;
data->o_audio2 = NULL;
return data;
}
static void myamp_connect_port(LADSPA_Handle Instance, unsigned long Port, LADSPA_Data *DataLocation)
{
MyAmpData *data = (MyAmpData*)Instance;
switch (Port)
{
case PORT_CAMP: data->c_amp = DataLocation; break;
case PORT_INPUT1: data->i_audio1 = DataLocation; break;
case PORT_INPUT2: data->i_audio2 = DataLocation; break;
case PORT_OUTPUT1: data->o_audio1 = DataLocation; break;
case PORT_OUTPUT2: data->o_audio2 = DataLocation; break;
}
}
static void myamp_run(LADSPA_Handle Instance, unsigned long SampleCount)
{
MyAmpData *data = (MyAmpData*)Instance;
double amp = *data->c_amp;
size_t i;
for (i = 0; i < SampleCount; i++)
{
data->o_audio1[i] = data->i_audio1[i]*amp;
data->o_audio2[i] = data->i_audio2[i]*amp;
}
}
static void myamp_cleanup(LADSPA_Handle Instance)
{
MyAmpData *data = (MyAmpData*)Instance;
free(data);
}
static LADSPA_Descriptor myampDescriptor = {
.UniqueID = 123, // for public release see http://ladspa.org/ladspa_sdk/unique_ids.html
.Label = "amp_example",
.Name = "My Amplify Plugin",
.Maker = "alsauser",
.Copyright = "WTFPL",
.PortCount = 5,
.PortDescriptors = (LADSPA_PortDescriptor[]){
LADSPA_PORT_INPUT | LADSPA_PORT_CONTROL,
LADSPA_PORT_INPUT | LADSPA_PORT_AUDIO,
LADSPA_PORT_INPUT | LADSPA_PORT_AUDIO,
LADSPA_PORT_OUTPUT | LADSPA_PORT_AUDIO,
LADSPA_PORT_OUTPUT | LADSPA_PORT_AUDIO
},
.PortNames = (const char * const[]){
"Amplification factor",
"Input left",
"Input right",
"Output left",
"Output right"
},
.PortRangeHints = (LADSPA_PortRangeHint[]){
{ /* PORT_CAMP */
LADSPA_HINT_BOUNDED_BELOW | LADSPA_HINT_BOUNDED_ABOVE | LADSPA_HINT_DEFAULT_1,
0, /* LowerBound*/
10 /* UpperBound */
},
{0, 0, 0}, /* PORT_INPUT1 */
{0, 0, 0}, /* PORT_INPUT2 */
{0, 0, 0}, /* PORT_OUTPUT1 */
{0, 0, 0} /* PORT_OUTPUT2 */
},
.instantiate = myamp_instantiate,
//.activate = myamp_activate,
.connect_port = myamp_connect_port,
.run = myamp_run,
//.deactivate = myamp_deactivate,
.cleanup = myamp_cleanup
};
// NULL-terminated list of plugins in this library
const LADSPA_Descriptor *ladspa_descriptor(unsigned long Index)
{
if (Index == 0)
return &myampDescriptor;
else
return NULL;
}
(如果你喜欢的“短” 40线版本见https://pastebin.com/unCnjYfD)
根据需要添加尽可能多的输入/输出通道,在myamp_run()函数中实现您的代码。构建插件和LADSPA_PATH环境变量设置为你建造它的目录,以便其他应用程序可以找到它:
export LADSPA_PATH=/usr/lib/ladspa:/full/path/to/plugindir
测试它audacity
或任何其他程序支持LADSPA插件。为了在终端测试它,你可以从“LADSPA-SDK”包中使用applyplugin
工具:
applyplugin input.wav output.wav /full/path/to/plugindir/amp_example.so amp_example 2
如果你喜欢的结果将其插入到您的默认播放链。对于纯ALSA你可以使用像配置(不适用于脉冲/插孔工作):
# ~/.asoundrc
pcm.myamp {
type plug
slave.pcm {
type ladspa
path "/usr/lib/ladspa" # required but ignored as `filename` is set
slave.pcm "sysdefault"
playback_plugins [{
filename "/full/path/to/plugindir/amp_example.so"
label "amp_example"
input.controls [ 2.0 ] # Amplification=2
}]
}
}
# to test it: aplay -Dmyamp input.wav
# to point "default" pcm to it uncomment next line:
#pcm.!default "myamp"
参见:
这听起来像是用于[外部过滤器插件]的作业(http://www.alsa-project.org/alsa-doc/alsa-lib/group___p_c_m___ext_plug.html)。 (例如,请参阅'upmix'或'vdownmix'插件。) –
我理解这个权利吗?来自http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_external_plugins.html中的文档:“过滤器类型的插件是一个插件,用于将来自输入和馈送的PCM信号转换为输出”。这不是我所追求的---我想拦截发送到输出的数据(来自图腾或VLC视频播放器;来自YouTube或一般来自网络浏览器;来自游戏等),修改它(包括改变频道数量等),并让它继续到达输出设备。我误解了吗?我可以通过外部过滤器插件来实现吗? –
这正是过滤器插件的功能; “输入”和“输出”不是指单独的设备,而是指数据流。 –