3.1 Constructors

MediaRecorder

Parameter	Type	Nullable	Optional	Description
stream	MediaStream	✘	✘	The MediaStream to be recorded. This will be the value of the stream attribute. See [GETUSERMEDIA] for the definition of MediaStream.
options	MediaRecorderOptions	✘	✔	A dictionary of options to for the UA instructing how the recording will take part. options.mimeType, if present, will become the value of mimeType attribute.

3.2 Attributes

audioBitsPerSecond of type unsigned long, readonly

The value of the Audio encoding target bit rate that was passed to the Platform (potentially truncated, rounded, etc), or the calculated one if the user has specified bitsPerSecond.

ignoreMutedMedia of type boolean

If this attribute is set to true, the MediaRecorder will not record anything when the input Media Stream is muted. If this attribute is false, the MediaRecorder will record silence (for audio) and black frames (for video) when the input MediaStream is muted. When the MediaRecorder is created, the UA must set this attribute to false.

mimeType of type DOMString, readonly

The MIME type that has been selected as the container for recording. This entry includes all the parameters to the base mimeType. The UA should be able to play back any of the MIME types it supports for recording. For example, it should be able to display a video recording in the HTML <video> tag. The default value for this property is platform-specific. Note that the mimeType specifies the container format for the recording, and that the codecs that the recording contains will normally be specified as parameters to it.

ondataavailable of type EventHandler

Called to handle the dataavailable event. Note that the Blob (see [FILE-API]) of recorded data is contained in this event and can be accessed via the 'data' attribute.

onerror of type EventHandler

Called to handle a ErrorEvent.

onpause of type EventHandler

Called to handle the pause event.

onresume of type EventHandler

Called to handle the resume event.

onstart of type EventHandler

Called to handle the start event.

onstop of type EventHandler

Called to handle the stop event.

state of type RecordingState, readonly

The current state of the MediaRecorder object. When the MediaRecorder is created, the UA must set this attribute to inactive.

stream of type MediaStream, readonly

The MediaStream to be recorded.

videoBitsPerSecond of type unsigned long, readonly

The value of the Video encoding target bit rate that was passed to the Platform (potentially truncated, rounded, etc), or the calculated one if the user has specified bitsPerSecond.

3.3 Methods

isTypeSupported, static

Check to see whether a MediaRecorder can record in the specified MIME type. If true is returned from this method, it only indicates that the MediaRecorder implementation is capable of recording Blob objects for the specified MIME type. Recording may still fail if sufficient resources are not available to support the concrete media encoding. When this method is invoked, the User Agent must run the following steps:

1. If type is an empty string, then return true (note that this case is essentially equivalent to leaving up to the UA the choice of container and codecs on constructor).
2. If type does not contain a valid MIME type string, then return false.
3. If type contains a media type or media subtype that the MediaRecorder does not support, then return false.
4. If type contains a media container that the MediaSource does not support, then return false.
5. If type contains a codec that the MediaSource does not support, then return false.
6. If the MediaRecorder does not support the specified combination of media type/subtype, codecs and container then return false.
7. Return true.

Parameter	Type	Nullable	Optional	Description
type	DOMString	✘	✘	A MIME Type, including parameters, specifying a container and/or codec formats for recording.

Return type: bool

pause

When a MediaRecorder object’s pause()method is invoked, the UA must queue a task, using the DOM manipulation task source, that runs the following steps:

1. If state is "inactive" throw an InvalidStateError DOMException and terminate these steps. Otherwise:
2. Set state to "paused".
3. Stop gathering data into its current Blob (but keep the Blob available so that recording can be resumed in the future).
4. Fire a pause event

No parameters.

Return type: void

requestData

When a MediaRecorderobject’s requestData() method is invoked, the UA must queue a task, using the DOM manipulation task source, that runs the following steps:

1. If state is not "recording" throw an InvalidStateError DOMException and terminate these steps. Otherwise:
2. Fire a dataavailable event containing the current Blob of saved data. (Note that this Blob will be empty if no data has been gathered yet.)
3. Create a new Blob and gather subsequent data into it.

No parameters.

Return type: void

resume

When a MediaRecorder object’s resume() method is invoked, the UA must queue a task, using the DOM manipulation task source, that runs the following steps:

1. If state is "inactive" throw an InvalidStateError DOMException and terminate these steps. Otherwise:
2. Set state to "recording".
3. Resume (or continue) gathering data into its current Blob.
4. Fire a resume event.

No parameters.

Return type: void

start

When a MediaRecorder object’s start() method is invoked, the UA must queue a task, using the DOM manipulation task source, that runs the following steps:

1. If the state is not "inactive", throw a InvalidStateError DOMException and terminate these steps. Otherwise:
2. Set state to 'recording' and wait until media becomes available from stream.
3. Once data becomes available fire a start event and start gathering the data into a Blob (see [FILE-API]).
4. If the timeSlice argument has been provided, then once timeSlice milliseconds of data have been colleced, or some minimum time slice imposed by the UA, whichever is greater, fire a dataavailable event containing the Blob of collected data, and start gathering a new Blob of data. Otherwise (if timeSlice has not been provided), continue gathering data into the original Blob.
5. When the stream is ended set recording to 'inactive' and stop gathering data. Callers should not rely on exactness of the timeSlice value, especially if the timeSlice value is small. Callers should consider timeSlice as a minimum value
6. Then fire a dataavailable event containing the Blob of data.
7. Finally, fire a stop event.

Note that stop(), requestData(), and pause() also affect the recording behavior.

The UA must record the MediaStream in such a way that the original Tracks can be retrieved at playback time. When multiple Blobs are returned (because of timeSlice or requestData), the individual Blobs need not be playable, but the combination of all the Blobs from a completed recording must be playable. If any Track within the MediaStream is muted at any time (i.e., if its readyState is set to muted), the UA must insert black frames or silence until the Track is unmuted.

If at any point the stream's isolation properties change so that MediaRecorder is no longer allowed access to it, the UA must stop recording, discard any data that it has gathered and throw a SecurityError DOMException followed by the stop event. If the UA is unable to start recording or at any point is unable to continue recording (i.e., for reasons other than a security violation), it must throw an UnknownError DOMException, followed by a dataavailable event containing the Blob it has gathered, follwed by the stop event.

Parameter	Type	Nullable	Optional	Description
timeslice	long	✘	✔	The number of milliseconds of data to return in a single Blob.

Return type: void

stop

When a MediaRecorder object’s stop method is invoked, the UA must queue a task, using the DOM manipulation task source, that runs the following steps:

1. If state is "inactive", throw a InvalidStateError DOMException and terminate these steps. Otherwise:
2. Set state to 'inactive' and stop gathering data.
3. Fire a dataavailable event containing the Blob of data that has been gathered.
4. Fire a stop event

No parameters.

Return type: void

3.4 MediaRecorderOptions

dictionary MediaRecorderOptions {
             DOMString     mimeType;
             unsigned long audioBitsPerSecond;
             unsigned long videoBitsPerSecond;
             unsigned long bitsPerSecond;
};

3.5 RecordingState

enum RecordingState {
    "inactive",
    "recording",
    "paused"
};

4.1 Constructors

BlobEvent

Parameter	Type	Nullable	Optional	Description
type	DOMString	✘	✘	Associated Event type.
eventInitDict	BlobEventInit	✘	✘	An initializer whose data field will be used to initialize the attribute of the same name.

4.2 Attributes

data of type Blob, readonly

Returns a Blob object whose type attribute indicates the encoding of the blob data.

4.3 Dictionary BlobEventInit Members

data of type Blob, required

A Blob object containing the data to deliver via this event.

5.1 General Principles

The UA must throw a DOMException (see [DOM4]) when the error can be detected at the time that the call is made. In all other cases, an ErrorEvent must be fired. If recording has been started and not yet stopped when the error occurs, then after raising the error, the UA must fire a dataavailable event, containing any data that it has gathered, and then a stop event. The UA may set platform-specific limits, such as those for the minimum and maximum Blob size that it will support, or the number of Tracks it will record at once. It must signal a fatal error if these limits are exceeded.

5.2 ErrorEvent

The following interface is defined for cases when an event is raised that could have been caused by an error:

Firing an error event named e with an Error error means that an event with the name e, which does not bubble (except where otherwise stated) and is not cancelable (except where otherwise stated), and which uses the ErrorEvent interface with the error attribute set to error, MUST be created and dispatched at the given target. If no Error object is specified, the error attribute defaults to null.

dictionary ErrorEventInit : EventInit {
             Error? error = null;
};

[Exposed=Window,
 Constructor (DOMString type, ErrorEventInit eventInitDict)]
interface ErrorEvent : Event {
    readonly        attribute Error? error;
};