XAudio2学习之音效相关结构体

任何XAudio2 voice都可以持有一个音频效果链。你可以使用XAUDIO2_EFFECT_DESCRIPTOR数组来指定效果链。每个描述因子都包含了由客户端提供的指向音效对象的指针。这些对象必须实现APO接口。

结构体定义为：

typedef struct XAUDIO2_EFFECT_DESCRIPTOR {
  IUnknown *pEffect;
  BOOL     InitialState;
  UINT32   OutputChannels;
} XAUDIO2_EFFECT_DESCRIPTOR;

第一个参数指向XAPO对象。第二个参数表示初始化状态，如果效果需要以可用的状态开始的话，那么此值为TRUE，否则为FALSE。第三个参数表示音效需要生成的通道数。

XAPO实例以IUnknown接口的形式传递给XAudio2。XAudio2可以使用 IXAPO::QueryInterface来获取IXAPO接口，并且检测IXAPO是否实现了 IXAPOParameters接口。

将XAPO对象传递给XAudio2后，需要设置具体的参数，关联已有的音效。参数的保存需要使用XAUDIO2FX_REVERB_PARAMETERS结构体。

结构体定义为：

typedef struct XAUDIO2FX_REVERB_PARAMETERS {
  float  WetDryMix;
  UINT32 ReflectionsDelay;
  BYTE   ReverbDelay;
  BYTE   RearDelay;
  BYTE   SideDelay;
  BYTE   PositionLeft;
  BYTE   PositionRight;
  BYTE   PositionMatrixLeft;
  BYTE   PositionMatrixRight;
  BYTE   EarlyDiffusion;
  BYTE   LateDiffusion;
  BYTE   LowEQGain;
  BYTE   LowEQCutoff;
  BYTE   HighEQGain;
  BYTE   HighEQCutoff;
  float  RoomFilterFreq;
  float  RoomFilterMain;
  float  RoomFilterHF;
  float  ReflectionsGain;
  float  ReverbGain;
  float  DecayTime;
  float  Density;
  float  RoomSize;
  BOOL   DisableLateField;
} XAUDIO2FX_REVERB_PARAMETERS;

WetDryMix

 Percentage of the output that will be reverb. Allowable values are from 0 to 100.

将要混响的输出的百分比。允许的数值是0~100.

ReflectionsDelay

The delay time of the first reflection relative to the direct path. Permitted range is from 0 to 300 milliseconds.

相对于直接路径，第一反射的延时。允许的变化范围是从0~300毫秒。

ReverbDelay

Delay of reverb relative to the first reflection. Permitted range is from 0 to 85 milliseconds.

混响相对于第一次反射的延时。允许的变化范围是0~85毫秒。

 

RearDelay

Delay for the left rear output and right rear output. Permitted range is from 0 to 5 milliseconds.

左后输出和右后输出的延迟。允许变化范围是0~5毫秒。

 

SideDelay

Delay for the left side output and right side output. Permitted range is from 0 to 5 milliseconds.

Note  This value is supported beginning with Windows 10.

 左边输出和右边输出的延迟。允许变化范围是0~5毫秒。

 

注意：这个值从win10开始支持。

PositionLeft

Position of the left input within the simulated space relative to the listener. With PositionLeft set to the minimum value, the left input is placed close to the listener. In this position, early reflections are dominant, and the reverb decay is set back in the sound field and reduced in amplitude. With PositionLeft set to the maximum value, the left input is placed at a maximum distance from the listener within the simulated room. PositionLeft does not affect the reverb decay time (liveness of the room), only the apparent position of the source relative to the listener. Permitted range is from 0 to 30 (no units).

在模拟空间中左输入相对于听者的位置。PositionLeft设置为最小值，左输入被放置在离听者近的位置。在这个位置，早期的反射占主导地位，且混响衰减在声音区域推迟并且在幅度上减少。PositionLeft设置为最大值，在模拟空间内左输入被放置在离听众最远的距离。PositionLeft不影响混响衰减时间（房间生命期），只是源相对于听者的明显位置。允许变化范围是0~30，无单位。

PositionRight

Same as PositionLeft, but affecting only the right input. Permitted range is from 0 to 30 (no units).

Note  PositionRight is ignored in mono-in/mono-out mode.

 

和 PositionLeft一样，但是只影响右输入。允许变化范围是0~30，无单位。

注意：单声道入或者单声道出模式下忽略此值。

PositionMatrixLeft

Gives a greater or lesser impression of distance from the source to the listener. Permitted range is from 0 to 30 (no units).

提供一种或多或少的距离上的感觉，从源到听众之间。允许变化范围是0~30，无单位。

PositionMatrixRight

Gives a greater or lesser impression of distance from the source to the listener. Permitted range is from 0 to 30 (no units).

Note   PositionMatrixRight is ignored in mono-in/mono-out mode.

  提供一种或多或少的距离上的感觉，从源到听众之间。 允许变化范围是0~30，无单位。

注意：单声道入或者单声道出模式下忽略此值。

EarlyDiffusion

Controls the character of the individual wall reflections. Set to minimum value to simulate a hard flat surface and to maximum value to simulate a diffuse surface. Permitted range is from 0 to 15 (no units).

控制单个墙壁反射的特性。最小值表示模拟坚硬平坦的表面，最大值表示模拟漫反射表面。允许变化范围是0~15，无单位。

LateDiffusion

Controls the character of the individual wall reverberations. Set to minimum value to simulate a hard flat surface and to maximum value to simulate a diffuse surface. Permitted range is from 0 to 15 (no units).

控制单个墙壁混响的特性。最小值表示模拟坚硬平坦的表面，最大值表示模拟漫反射表面。允许变化范围是0~15，无单位。

LowEQGain

Adjusts the decay time of low frequencies relative to the decay time at 1 kHz. The values correspond to dB of gain as follows:

调整低频率的衰减时间，相对于1kHz时的衰减时间。值相对于增益的分贝如下：

Value	0	1	2	3	4	5	6	7	8	9	10	11	12
Gain (dB)	-8	-7	-6	-5	-4	-3	-2	-1	0	+1	+2	+3	+4

Note  A  LowEQGain value of 8 results in the decay time of low frequencies being equal to the decay time at 1 kHz.

 

Permitted range is from 0 to 12 (no units).

LowEQGain的值为8时，作用在低频率的衰减时间和1kHz时的衰减时间相等。允许变化范围是0~12，无单位。

LowEQCutoff

Sets the corner frequency of the low pass filter that is controlled by the LowEQGain parameter. The values correspond to frequency in Hz as follows:

设置由 LowEQGain参数控制的低通滤波器的拐角频率。值对应频率如下：

Value	0	1	2	3	4	5	6	7	8	9
Frequency (Hz)	50	100	150	200	250	300	350	400	450	500

Permitted range is from 0 to 9 (no units).

允许变化范围是0~9，无单位。

HighEQGain

Adjusts the decay time of high frequencies relative to the decay time at 1 kHz. When set to zero, high frequencies decay at the same rate as 1 kHz. When set to maximum value, high frequencies decay at a much faster rate than 1 kHz.

调整低频率的衰减时间，相对于1kHz时的衰减时间。当设置为0时，高频衰减和1kHz时的速率相同。当设置为最大值时，高频衰减比1kHz的速率快很多。

Value	0	1	2	3	4	5	6	7	8
Gain (dB)	-8	-7	-6	-5	-4	-3	-2	-1	0

Permitted range is from 0 to 8 (no units).

允许变化范围是0~8，无单位。

HighEQCutoff

Sets the corner frequency of the high pass filter that is controlled by the HighEQGain parameter. The values correspond to frequency in kHz as follows:

设置由 HighEQGain 参数控制的低通滤波器的拐角频率。值对应频率如下：

Value	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14
Frequency (kHz)	1	1.5	2	2.5	3	3.5	4	4.5	5	5.5	6	6.5	7	7.5	8

Permitted range is from 0 to 14 (no units).

允许变化范围是0~14，无单位。

RoomFilterFreq

Sets the corner frequency of the low pass filter for the room effect. Permitted range is from 20 to 20,000 Hz.

为空间效果设置低通滤波器的拐角频率。 允许变化范围是20~20,000Hz。

 

RoomFilterMain

Sets the pass band intensity level of the low-pass filter for both the early reflections and the late field reverberation. Permitted range is from -100 to 0 dB.

为早期反射和晚期区域回响设置低通滤波器的传动带强度水平。允许变化范围是-100~0dB.

RoomFilterHF

Sets the intensity of the low-pass filter for both the early reflections and the late field reverberation at the corner frequency (RoomFilterFreq). Permitted range is from -100 to 0 dB.

在拐角频率基础上为早期反射和晚期区域回响设置低通滤波器的强度。允许变化范围是-100~0dB.

ReflectionsGain

Adjusts the intensity of the early reflections. Permitted range is from -100 to 20 dB.

调节早期反射的强度。允许变化范围是-100~20dB.

ReverbGain

Adjusts the intensity of the reverberations. Permitted range is from -100 to 20 dB.

调节混响的强度。允许变化范围是-100~20dB.

DecayTime

Reverberation decay time at 1 kHz. This is the time that a full scale input signal decays by 60 dB. Permitted range is from 0.1 to infinity seconds.

1Hz时的回响衰减时间。这是完全比例的输入信息衰减60dB的时间。允许变化范围是0.1到无穷大秒。

Density

Controls the modal density in the late field reverberation. For colorless spaces, Density should be set to the maximum value (100). As Density is decreased, the sound becomes hollow (comb filtered). This is an effect that can be useful if you are trying to model a silo. Permitted range as a percentage is from 0 to 100.

控制晚场混响的模态密度。对于无色彩的空间，密度应该设置为最大值100.随着密度减少，声音变为中空（梳状滤波）。如果你想要创建一个筒状模型，这是非常有用的效果。允许变化百分比是0~100.

RoomSize

The apparent size of the acoustic space. Permitted range is from 1 to 100 feet.

听觉空间的明显尺寸。允许变化范围是1~100英尺。

DisableLateField

If set to TRUE, disables late field reflection calculations. Disabling late field reflection calculations results in a significant CPU time savings.

Note  The DirectX SDK versions of XAUDIO2 don't support this member.

 

如果设置为TRUE，禁止晚场反射计算。禁止晚场反射计算可以带来很大的CPU时间节省。

注意：XAudio2的DirectX SDK版本不支持这个成员。

Remarks

All parameters related to sampling rate or time are relative to a 48kHz voice and must be scaled for use with other sampling rates. For example, setting ReflectionsDelay to 300ms gives a true 300ms delay when the reverb is hosted in a 48kHz voice, but becomes a 150ms delay when hosted in a 24kHz voice.

所有和采样率或者时间相关的参数都是相对于48kHz的 voice，如果使用其他采样率，必须进行缩放。例如，设置 ReflectionsDelay 为300ms,当混响被一个48kHz的voice持有时就会出现真实的300ms的延时，但是如果24kHz 的voice持有的话，那么就是150ms的延迟。

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