AudioBufferSourceNode: start() method
The start()
method of the AudioBufferSourceNode
Interface is used to schedule playback of the audio data contained in the buffer, or
to begin playback immediately.
Syntax
js
start(when)
start(when, offset)
start(when, offset, duration)
Parameters
when
Optional-
The time, in seconds, at which the sound should begin to play, in the same time coordinate system used by the
AudioContext
. Ifwhen
is less than (AudioContext.currentTime
, or if it's 0, the sound begins to play at once. The default value is 0. offset
Optional-
An offset, specified as the number of seconds in the same time coordinate system as the
AudioContext
, to the time within the audio buffer that playback should begin. For example, to start playback halfway through a 10-second audio clip,offset
should be 5. The default value, 0, will begin playback at the beginning of the audio buffer, and offsets past the end of the audio which will be played (based on the audio buffer'sduration
and/or theloopEnd
property) are silently clamped to the maximum value allowed. The computation of the offset into the sound is performed using the sound buffer's natural sample rate, rather than the current playback rate, so even if the sound is playing at twice its normal speed, the midway point through a 10-second audio buffer is still 5. duration
Optional-
The duration of the sound to be played, specified in seconds. If this parameter isn't specified, the sound plays until it reaches its natural conclusion or is stopped using the
stop()
method. Using this parameter is functionally identical to callingstart(when, offset)
and then callingstop(when+duration)
.
Return value
None (undefined
).
Exceptions
TypeError
-
Thrown if a negative value was specified for one or more of the three time parameters. Please don't attempt to tamper with the laws of temporal physics.
InvalidStateError
DOMException
-
Thrown if
start()
has already been called. You can only call this function once during the lifetime of anAudioBufferSourceNode
.
Examples
The most simple example just starts the audio buffer playing from the beginning — you don't need to specify any parameters in this case:
js
source.start();
The following more complex example will, 1 second from now, start playing 10 seconds worth of sound starting 3 seconds into the audio buffer.
js
source.start(audioCtx.currentTime + 1, 3, 10);
Note: For a more complete example showing start()
in use, check out our AudioContext.decodeAudioData()
example. You can also run the code example live, or view the source.
Specifications
Specification |
---|
Web Audio API # dom-audiobuffersourcenode-start |
Browser compatibility
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