更改话筒增益编程在OSX
问题描述:
答
看来,改变音量增益是不可能在飞行时AudioQueue运行,一些如何能够增加麦克风增益缓冲器,张贴代码,
void AQRecorder::setGain(void *data, int bytes, float gain){
SInt16 *editBuffer = (SInt16 *)data;
// loop over every packet
for (int nb = 0; nb < (bytes/2); nb++) {
// we check if the gain has been modified to save resoures
if (gain != 0) {
// we need more accuracy in our calculation so we calculate with doubles
double gainSample = ((double)editBuffer[nb])/32767.0;
/*
at this point we multiply with our gain factor
we dont make a addition to prevent generation of sound where no sound is.
no noise
0*10=0
noise if zero
0+10=10
*/
gainSample *= gain;
/**
our signal range cant be higher or lesser -1.0/1.0
we prevent that the signal got outside our range
*/
gainSample = (gainSample < -1.0) ? -1.0 : (gainSample > 1.0) ? 1.0 : gainSample;
/*
This thing here is a little helper to shape our incoming wave.
The sound gets pretty warm and better and the noise is reduced a lot.
Feel free to outcomment this line and here again.
You can see here what happens here http://silentmatt.com/javascript-function-plotter/
Copy this to the command line and hit enter: plot y=(1.5*x)-0.5*x*x*x
*/
gainSample = (1.5 * gainSample) - 0.5 * gainSample * gainSample * gainSample;
// multiply the new signal back to short
gainSample = gainSample * 32767.0;
// write calculate sample back to the buffer
editBuffer[nb] = (SInt16)gainSample;
}
}
}
记住此功能只应叫当有一个增益变化,否则保存CPU资源..
答
首先,问你的队列其kAudioQueueProperty_CurrentDevice
,这是它的读取设备的标识字符串。
接下来,您需要打开该设备。这是比它应该做的更多的工作,因为Core Audio的设计人员通过通用的“GetProperty”和“SetProperty”功能相信所有事情都做得很好。这里所说:
- 创建包含一个指向包含设备标识符和一个指向您希望
AudioDeviceID
变量的变量的AudioValueTranslation
结构。 - 使用
AudioHardwareGetProperty
或未被弃用,但更通用的AudioObjectGetProperty
得到kAudioHardwarePropertyDeviceForUID
,将指针传递给结构。 HAL将查找设备,并通过放置在结构中的指针将其返回给您。
如果这没有返回错误,您现在有一个设备。
最后一步是设置其增益。我认为这是显示为kAudioDevicePropertyVolumeScalar
上的输入范围,但我不是100%确定。无论如何,你会修补AudioDeviceSetProperty
和/或AudioObjectSetProperty
,直到找到合适的组合。
,非常感谢,我会试一试 – Amitg2k12 2013-02-28 03:47:54
我试过了,但我不能AudioObjectHasProperty总是返回麦克风错误,此外,我需要做它当AudioQueue运行:(,有一些解决方法张贴在这里... – Amitg2k12 2013-03-01 03:09:41