The decodingInfo() method of the MediaCapabilities interface returns a promise that fulfils with information about how well the user agent can decode/display media with a given configuration.
The encodingInfo() method of the MediaCapabilities interface returns a promise that fulfills with the tested media configuration's capabilities for encoding media. This contains the three boolean properties supported, smooth, and powerefficient, which describe how compatible the device is with the type of media.
The
MediaCapabilitiesinterface of the Media Capabilities API provides information about the decoding abilities of the device, system and browser. The API can be used to query the browser about the decoding abilities of the device based on codecs, profile, resolution, and bitrates. The information can be used to serve optimal media streams to the user and determine if playback should be smooth and power efficient.MDN Reference