AudioNode

AudioNode 接口是一个处理音频的通用模块, 比如一个音频源 (e.g. 一个 HTML <audio> or <video> 元素), 一个音频地址或者一个中间处理模块 (e.g. 一个过滤器如 BiquadFilterNode, 或一个音量控制器如 GainNode).

一个AudioNode 既有输入也有输出. 输入与输出都有一定数量的通道. An AudioNode with zero input and exactly one output is called a source node.

The processing varies from one AudioNode to another but, in general, a node reads its inputs, does some audio-related processing, and generates new values on its output.

Different nodes can be linked together to build a processing graph. Such a graph is contained in an AudioContext. Each AudioNode participates in exactly one such context.

An AudioNode can be target of events, therefore it implements the EventTarget interface.

属性

AudioNode.context 只读

链接到关联的 AudioContext, that is the object representing the processing graph the node is participating in.

AudioNode.numberOfInputs 只读

返回这个node需要的输入数量. Source nodes are defined as nodes having a numberOfInputs attributes with a value of 0.

AudioNode.numberOfOutputs 只读

返回这个node的输出数量. Destination nodes, like AudioDestinationNode, have a value of 0 for this attribute.

AudioNode.channelCount

Represents an integer used in determining how many channels outputs must contains. Its usage and precise definition depends of the value of AudioNode.channelCountMode: it is ignored if the value is "max", used as a maximum value for "clamped-max", or used as the effective value for "explicit".

AudioNode.channelCountMode

Represents an enumerated value describing the way channels must be matched between the inputs and the outputs. Possible values are:

Value	Description	Used as default for the following AudioNode children
"max"	The number of channels is the maximum of the number of channels all connections. That implies that channelCount is ignored and only up-mixing happens	GainNode, DelayNode, ScriptProcessorNode, ChannelSplitterNode, ChannelMergerNode, BiquadFilterNode, WaveShaperNode
"clamped-max"	The number of channels is the maximum of the number of channels of all connections, clamped to the value of channelCount.	PannerNode, ConvolverNode
"explicit"	The number of channels is defined by the value of channelCount.	AudioDestinationNode, AnalyserNode, DynamicsCompressorNode

AudioNode.channelInterpretation

Represents an enumerated value describing the meaning of the channels. This interpretation will define how the up-mixing and the down-mixing will happen.
The possible values are "speakers" or "discrete". In the case of "speakers", the ordering of the channels have the following meaning, and the channels are often represented by a standard abbreviation:

Mono	0: M: mono
Stereo	0: L: left 1: R: right
Quad	0: L:  left 1: R:  right 2: SL: surround left 3: SR: surround right
5.1	0: L:   left 1: R:   right 2: C:   center 3: LFE: subwoofer 4: SL:  surround left 5: SR:  surround right

When the amount of channels doesn't match between an input and an output, up- or down-mixing happens according the following rules:

Interpretation	Input channels	Output channels	Mixing rules
speakers	1 (Mono)	2 (Stereo)	Up-mix from mono to stereo. The M input channel is used for both output channels (L and R). output.L = input.M output.R = input.M
	1 (Mono)	4 (Quad)	Up-mix from mono to quad. The M input channel is used for non-surround output channels (L and R). Surround output channels (SL and SR) are silent. output.L  = input.M output.R  = input.M output.SL = 0 output.SR = 0
	1 (Mono)	6 (5.1)	Up-mix from mono to 5.1. The M input channel is used for the center output channel (C). All the others (L, R, LFE, SL, and SR) are silent. output.L   = 0 output.R   = 0 output.C   = input.M output.LFE = 0 output.SL  = 0 output.SR  = 0
	2 (Stereo)	1 (Mono)	Down-mix from stereo to mono. Both input channels (L and R) are equally combined to produce the unique output channel (M). output.M = 0.5 * (input.L + input.R)
	2 (Stereo)	4 (Quad)	Up-mix from stereo to quad. The L and R input channels are used for their non-surround respective output channels (L and R). Surround output channels (SL and SR) are silent. output.L  = input.L output.R  = input.R output.SL = 0 output.SR = 0
	2 (Stereo)	6 (5.1)	Up-mix from stereo to 5.1. The L and R input channels are used for their non-surround respective output channels (L and R). Surround output channels (SL and SR), as well as the center (C) and subwoofer (LFE) channels, are left silent. output.L   = input.L output.R   = input.R output.C   = 0 output.LFE = 0 output.SL  = 0 output.SR  = 0
	4 (Quad)	1 (Mono)	Down-mix from quad to mono. All four input channels (L, R, SL, and SR) are equally combined to produce the unique output channel (M). output.M = 0.25 * (input.L + input.R + input.SL + input.SR)
	4 (Quad)	2 (Stereo)	Down-mix from quad to mono. Both left input channels (L and SL) are equally combined to produce the unique left output channel (L). And similarly, both right input channels (R and SR) are equally combined to produce the unique right output channel (R). output.L = 0.5 * (input.L + input.SL) output.R = 0.5 * (input.R + input.SR)
	4 (Quad)	6 (5.1)	Up-mix from quad to 5.1. The L, R, SL, and SR input channels are used for their respective output channels (L and R). Center (C) and subwoofer (LFE) channels are left silent. output.L   = input.L output.R   = input.R output.C   = 0 output.LFE = 0 output.SL  = input.SL output.SR  = input.SR
	6 (5.1)	1 (Mono)	Down-mix from 5.1 to stereo. The left and right, both surround or not, and the central channels are all mixed together. The surround channels are slightly attenuated and the regular lateral channels are power-compensated to make them count as a single channel. The subwoofer (LFE) channel is lost. output.M = 0.7071 * (input.L + input.R) + input.C + 0.5 * (input.SL + input.SR)
	6 (5.1)	2 (Stereo)	Down-mix from 5.1 to stereo. The central (C) is summed with each lateral surround channels (SL or SR) and mixed to each lateral channel. As it is mixed in two channels, it is mixed at lower power, that is they are multiplied by √2/2. The subwoofer (LFE) channel is lost. output.L   = input.L + 0.7071 * (input.C + input.SL) output.R   = input.R + 0.7071 * (input.C + input.SR)
	6 (5.1)	4 (Quad)	Down-mix from 5.1 to quad. The central (C) is mixed with the lateral non-surround channels (L and R). As it is mixed in two channels, it is mixed at lower power, that is they are multiplied by √2/2. The surround channels are passed unchanged. The subwoofer (LFE) channel is lost. output.L   = input.L + 0.7071 * input.C output.R   = input.R output.SL  = input.SL output.SR  = input.SR
	Other		As these are non-standard channel layout, they are handled as if channelInterpretation was set to discrete. The specification explicitly allow the future definition of new speakers layout. This fallback is therefore not future proof as the behavior of the browsers for a specific amount of channels may change in the future.
discrete	any (x)	any (y) where x<y	Up-mix discrete channels. Fill each output channel with its input counterpart, that is the input channel with the same index. Channels with no corresponding input channels are left silent.
	any (x)	any (y) where x>y	Down-mix discrete channels. Fill each output channel with its input counterpart, that is the input channel with the same index. Input channels with no corresponding output channels are dropped.

方法

Also implements methods from the interface EventTarget.

AudioNode.connect(AudioNode)

Allows to connect one output of this node to one input of another node.

AudioNode.connect(AudioParam)

Allows to connect one output of this node to one input of an audio parameter.

AudioNode.disconnect()

Allows to disconnect this node from another one.

例子

规范

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相关内容

• Using Web Audio