PlaybackRate

I was asked an interesting question on Thursday after I showed my HTML5 video demo. Q: If you use playbackrate to fast forward video does the property have a max value setting? Reading through the W3C spec I couldn’t find anything specific.

Although the following paragraph seems to suggest that the rate can be set to whatever, but if it is too high then audio should be muted.

“When the [playbackRate](http://dev.w3.org/html5/spec/#dom-media-playbackrate) is negative (playback is backwards), any corresponding audio must be muted. When the [playbackRate](http://dev.w3.org/html5/spec/#dom-media-playbackrate) is so low or so high that the user agent cannot play audio usefully, the corresponding audio must also be muted. If the [playbackRate](http://dev.w3.org/html5/spec/#dom-media-playbackrate) is not 1.0, the user agent may apply pitch adjustments to the audio as necessary to render it faithfully.”

I tried this in IE9 and set the Playbackrate to 20000 (document.getElementById("mVideo").playbackRate = 20000)

IE9 seemed to fast-forward the video to a watchable but very fast speed, there was no notable difference between setting it at 20 and 20000. So I am assuming there is a max setting somewhere.

So in answer to the question. Nothing bad will happen in the current IE9 beta but at this point I don’t know for sure if their is a  Max value setting somewhere (I will find out and update)

Published by thebeebs

Martin works for Oracle as a Developer Evangelist. He’s been a developer since the late 90s and loves figuring out problems and experimenting with code. Read more