Media Capture and Streams API (Media Stream) - Web APIs 编辑

The Media Capture and Streams API, often called the Media Streams API or MediaStream API, is an API related to WebRTC which provides support for streaming audio and video data. It provides the interfaces and methods for working with the streams and their constituent tracks, the constraints associated with data formats, the success and error callbacks when using the data asynchronously, and the events that are fired during the process.

Concepts and usage

The API is based on the manipulation of a MediaStream object representing a flux of audio- or video-related data. See an example in Get the video.

A MediaStream consists of zero or more MediaStreamTrack objects, representing various audio or video tracks. Each MediaStreamTrack may have one or more channels. The channel represents the smallest unit of a media stream, such as an audio signal associated with a given speaker, like left or right in a stereo audio track.

MediaStream objects have a single input and a single output. A MediaStream object generated by getUserMedia() is called local, and has as its source input one of the user's cameras or microphones. A non-local MediaStream may be representing to a media element, like <video> or <audio>, a stream originating over the network, and obtained via the WebRTC RTCPeerConnection API, or a stream created using the Web Audio API MediaStreamAudioSourceNode.

The output of the MediaStream object is linked to a consumer. It can be a media elements, like <audio> or <video>, the WebRTC RTCPeerConnection API or a Web Audio API MediaStreamAudioSourceNode.

Interfaces

In these reference articles, you'll find the fundamental information you'll need to know about each of the interfaces that make up the Media Capture and Streams API.

• BlobEvent
• CanvasCaptureMediaStreamTrack
• InputDeviceInfo
• MediaDeviceKind
• MediaDeviceInfo
• MediaDevices
• MediaStream
• MediaStreamConstraints
• MediaStreamEvent
• MediaStreamTrack
• MediaStreamTrackEvent
• MediaTrackCapabilities
• MediaTrackConstraints
• MediaTrackSettings
• MediaTrackSupportedConstraints
• NavigatorUserMedia
• NavigatorUserMediaError
• OverconstrainedError
• URL

Early versions of the Media Capture and Streams API specification included separate AudioStreamTrack and VideoStreamTrack interfaces—each based upon MediaStreamTrack—which represented streams of those types. These no longer exist, and you should update any existing code to instead use MediaStreamTrack directly.

Events

• addtrack
• ended
• muted
• overconstrained
• removetrack
• started
• unmuted

Guides and tutorials

The articles below provide additional guidance and how-to information that will help you learn to use the API, and how to perform specific tasks that you may wish to handle.

Capabilities, constraints, and settings

The twin concepts of constraints and capabilities let the browser and Web site or app exchange information about what constrainable properties the browser's implementation supports and what values it supports for each one. This article discusses capabilities and constraints, as well as media settings, and includes an example we call the Example Constraint exerciser.

Browser compatibility

BCD tables only load in the browser

See also

• WebRTC - the introductory page to the API
• mediaDevices.getUserMedia()
• Taking still photos with WebRTC: a demonstration and tutorial about using getUserMedia().