Media Recording API

2.1 Attributes

mediaStream of type MediaStream, readonly

The MediaStream passed in to the constructor.

recording of type Boolean, readonly

True if 'record()' has been called and not stopped. Otherwise False.

onrecording of type EventHandler

Called to handle the recording event.

onstoprecording of type EventHandler

Called to handle the stoprecording event.

ondataavailable of type EventHandler

Called to handle the dataavailable event. Note that the Blob (see FILEAPI) of recorded data is contained in this event and can be accessed via the 'detail' attribute.

onrecordingerror of type EventHandler

Called to handle the recordingerror event.

onrecordingwarning of type EventHandler

Called to handle the recordingwarning event.

2.2 Methods

record

When a MediaRecorder object’s record() method is invoked, the user agent must queue a task that runs the following steps:

1. If recording is 'true', raise a recordingwarning event and abort these steps.
2. Otherwise set recording to 'true' and wait until media becomes available from mediaStream.
3. Once data becomes available raise a recordingevent and start gathering the data into a Blob (see FILEAPI).
4. If the timeSlice argument has been provided, then once timeSlice milliseconds of data have been colleced, raise 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 mediaStream is ended set recording to 'false' and stop gathering data.
6. Then raise a dataavailable event containing the Blob of data.
7. Finally, raise a stoprecording event.

Note that the stopRecording() and requestData() 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. If any Track within the MediaStream is muted, the UA must insert black frames or silence until the Track is unmuted. If the UA is unable to start recording or at any point is unable to contine recording, it must raise a recordingerror event, follwowed by a dataavailable event containing the Blob it has gathered, follwed by the stoprecording event.

stopRecording

When a MediaRecorder object’s stopRecording method is invoked, the user agent must queue a task that runs the following steps:

1. If recording is 'false', raise a recordingwarning event and abort these steps.
2. Set recording to 'false' and stop gathering data.
3. Raise a dataavailable event containing the Blob of data that has been gathered.
4. Raise a recordingdone event

requestData

When a MediaRecorder object’s requestData() method is invoked, the user agent must queue a task that runs the following steps:

1. If recording is 'false', raise a recordingwarning event and abort these steps.
2. Raise a dataavailable event containing the current Blob of saved data.
3. Creat a new Blob and gather subsequent data into it.

getRecordingOptions

When a MediaRecorder object’s getRecordingOptions() method is invoked, the user agent must return a availableRecordingFormats structure containing the set of recording formats that it supports.

setRecordingOptions

When a MediaRecorder object’s setRecordingOptions() method is invoked, the user agent must run the following steps:

1. If recording is 'true', raise a recordingwarning event and abort these steps.
2. Otherwise let encodings be the current set of encodings that are specified to be used for recording by the MediaRecorder. (If setRecordingOptions() has not yet been called, these will be the UA's defaults.)
3. For each encoding format that is specified in the requestedFormats argument, if the UA does not support it, raise a recordingwarning event, set encodings back to its value in step 2, and terminate these steps. Otherwise replace the corresponding member of encodings with the specified value.

3.0 Dictionary AvailableRecordingFormats

dictionary AvailableRecordingFormats {
    sequence<DOMString> containerEncodingFormats;
    sequence<DOMString> audioEncodingFormats;
    sequence<DOMString> videoEncodingFormats;
};

containerEncodingFormats of type sequence<DOMtring>

A list of the container encoding formats that the platform supports.

audioEncodingFormats of type sequence<DOMtring>

A list of the audio encoding formats that the platform supports.

videoEncodingFormats of type sequence<DOMtring>

A list of the video encoding formats that the platform supports.

The UA must be able to play back any encoding format that it can record into. The UA must support a container format capable of holding at least two video Tracks and two audio Tracks.

3.1 Dictionary RecordingFormat

dictionary RecordingFormat {
    <DOMString> containerEncodingFormat;
    <DOMString> audioEncodingFormat;
    <DOMString> videoEncodingFormat;
};

containerEncodingFormat of type <DOMtring>

The container encoding format to use for recording. If it is not specified, the platform default will be used.

audioEncodingFormat of type <DOMtring>

The audio encoding format to use for recording. If it is not specified, the platform default will be used.

videoEncodingFormat of type <DOMtring>

The video encoding format to use for recording. If it is not specified, the platform default will be used.