The MediaTrackSettings dictionary's sampleRate property is an integer indicating how many audio samples per second the MediaStreamTrack is currently configured for. This lets you determine what value was selected to comply with your specified constraints for this property's value as described in the MediaTrackConstraints.sampleRate property you provided when calling either getUserMedia() or MediaStreamTrack.applyConstraints().

If needed, you can determine whether or not this constraint is supported by checking the value of MediaTrackSupportedConstraints.sampleRate as returned by a call to MediaDevices.getSupportedConstraints(). However, typically this is unnecessary since browsers will ignore any constraints they're unfamiliar with.

An integer value indicating how many samples each second of audio data includes. Common values include 44,100 (standard CD audio), 48,000 (standard digital audio), 96,000 (commonly used in audio mastering and post-production), and 192,000 (used for high-resolution audio in professional recording and mastering sessions). However, lower values are often used to reduce bandwidth requirements; 8,000 samples per second is adequate for comprehensible albeit imperfect human speech, and both 11,025 FPS and 22,050 FPS are often used for low-bandwidth, reduced quality sound and music.

See the Constraint exerciser example.

• Media Capture and Streams API
• Capabilities, constraints, and settings
• MediaTrackConstraints.sampleRate
• MediaTrackSettings