媒体捕捉与媒体流 API(媒体流)

媒体捕捉与媒体流 API(Media Capture and Streams API),通常被称为媒体流 API(Media Streams API、MediaStream API),是与 WebRTC 相关的 API,提供对音频或视频数据流的支持。

它提供了用于处理媒体流及其组成轨道的接口和方法、与数据格式相关的约束、异步使用数据时成功和错误的回调以及在处理期间触发的事件。

概念和用法

这个 API 基于对表示音视频相关数据流的 MediaStream 对象的所有操作。参见获取媒体流中的示例。

一个 MediaStream 包含零个或多个代表各种声音和视频轨道MediaStreamTrack 对象。每一个 MediaStreamTrack 可能有一个或多个通道。这个通道代表着媒体流的最小单元,比如一个音频信号对应着一个对应的扬声器,像是在立体声道中的声道或声道。

MediaStream 对象有着单一的输入输出。由 getUserMedia() 创建的 MediaStream 对象是在本地借助用户相机和麦克风的源输入。非本地的 MediaStream 可能代表一个媒体元素(如 <video><audio>),或是一个通过 WebRTC RTCPeerConnection API 获得的源自网络的媒体流,又或是一个使用 Web 音频 APIMediaStreamAudioDestinationNode 创建的媒体流。

MediaStream 对象的输出能连接到一个消费端(consumer)。它可以是一个媒体元素(如 <audio><video>),也可以是 WebRTC RTCPeerConnection API 或 Web 音频 APIMediaStreamAudioSourceNode

接口

事件

指南和教程

功能、约束和设置文章讨论了约束功能以及媒体设置的概念,并包含了一个约束练习器,它允许你尝试应用于来自计算机音视频输入设备(如网络摄像头和麦克风)的音频和视频轨道的不同约束集的结果。

使用 getUserMedia() 拍摄静态照片文章展示了如何使用 getUserMedia() 来访问支持 getUserMedia() 的计算机或移动设备上的摄像头,并使用它拍摄照片。

浏览器兼容性

api.MediaStream

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MediaStream
MediaStream() constructor
active
active event
Non-standard
addTrack
addtrack event
clone
getAudioTracks
getTrackById
getTracks
getVideoTracks
id
inactive event
Non-standard
removeTrack
removetrack event

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Full support
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No support
Non-standard. Check cross-browser support before using.
See implementation notes.
Requires a vendor prefix or different name for use.
Has more compatibility info.

api.MediaStreamTrack

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MediaStreamTrack
applyConstraints
aspectRatio constraint
autoGainControl constraint
channelCount constraint
deviceId constraint
displaySurface constraint
echoCancellation constraint
facingMode constraint
frameRate constraint
groupId constraint
height constraint
latency constraint
logicalSurface constraint
noiseSuppression constraint
resizeMode constraint
sampleRate constraint
sampleSize constraint
suppressLocalAudioPlayback constraint
Experimental
volume constraint
DeprecatedNon-standard
width constraint
capturehandlechange event
Experimental
clone
contentHint
enabled
ended event
getCapabilities
getCaptureHandle
Experimental
getConstraints
getSettings
id
kind
label
mute event
muted
readyState
stop
unmute event

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Full support
Partial support
Partial support
No support
No support
Experimental. Expect behavior to change in the future.
Non-standard. Check cross-browser support before using.
Deprecated. Not for use in new websites.
See implementation notes.
Requires a vendor prefix or different name for use.
Has more compatibility info.

api.MediaDevices

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MediaDevices
devicechange event
enumerateDevices
getDisplayMedia()
Audio capture support
controller option
Experimental
monitorTypeSurfaces option
Experimental
preferCurrentTab option
ExperimentalNon-standard
selfBrowserSurface option
Experimental
surfaceSwitching option
Experimental
systemAudio option
Experimental
getSupportedConstraints
getUserMedia
Secure context required
selectAudioOutput
Experimental
setCaptureHandleConfig
Experimental

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Experimental. Expect behavior to change in the future.
Non-standard. Check cross-browser support before using.
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Has more compatibility info.

api.MediaDeviceInfo

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MediaDeviceInfo
deviceId
groupId
kind
label
toJSON()

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Full support
See implementation notes.

api.InputDeviceInfo

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InputDeviceInfo
getCapabilities

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api.CanvasCaptureMediaStreamTrack

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CanvasCaptureMediaStreamTrack
canvas
requestFrame

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参见